Quick Summary

Concealed vertical rod devices look like the obvious choice right up until the first service call. They give you a clean pair of doors with nothing running up the face, and then eighteen months later the top latch stops engaging and nobody can work out how to get at the rod.

This guide explains what the device is actually doing, where it is the right answer, where it is not, and how to work through the latching problems that make up most of the service work on these openings.

What Is a Concealed Vertical Rod Exit Device?

A concealed vertical rod exit device, usually shortened to CVR, is an exit device that latches the door at two points: a latch at the top that engages a strike in the frame head, and a latch at the bottom that engages a strike in the threshold or floor.

The two latches are driven by rods that run from the device up and down inside the door. Pushing the touchpad pulls both rods at once, retracting both latches, and the door is free.

The word that does the work is concealed. On a surface vertical rod device, the same mechanism exists but the rods are visible on the face of the door, held in place by brackets. On a CVR device the rods live inside the door and nothing shows.

How Does a CVR Device Latch the Door?

Three parts have to agree for the door to latch: the latch itself, the rod that drives it, and the strike it engages. If any one of those three is out of position the door will not stay shut, and all three are adjustable.

The top latch engages a strike mounted in the frame head. The bottom latch engages a strike set into the threshold, or in some configurations drops into a floor socket.

Why two latching points changes the behaviour

A rim device has one latch. If it engages, the door is shut. A CVR device has two, and the door can appear shut while only one of them is doing anything.

That is the source of most CVR confusion. Somebody pulls the door and it holds, so the device is assumed to be working, when in fact only the top latch is engaging and the bottom latch has been missing its strike for months.

CVR vs SVR vs Rim vs Mortise: Which Device Type Is on Your Door?

Identification takes about ten seconds once you know what to look at, and it has to be settled before any part is ordered because the latching components differ completely between configurations.

Pairs of doors are the usual home for vertical rod devices, because without a mullion between the leaves there is nothing in the middle for a rim latch to engage. Our mullion guide covers the alternative approach to the same problem.

If you have established that the device is rim rather than vertical rod, our rim exit device guide is the better starting point.

Why Would You Specify Concealed Vertical Rod?

Three reasons come up repeatedly, and they are all good ones.

Appearance is the first. On a glazed entrance or a prestigious opening, rods running up and down the face of the leaf are the visual element nobody wants. Concealing them leaves a clean door.

Protection is the second. Exposed rods get knocked by trolleys, caught by luggage and bent by people pushing on them. Rods inside the door cannot be reached, so they cannot be damaged by ordinary traffic.

Security is the third. There is nothing on the surface to interfere with, which matters on doors that are accessible to the public outside staffed hours.

What Are the Drawbacks of CVR?

The drawbacks are all versions of the same thing: the parts you most need to reach are the ones you cannot see.

That last point is the one that catches specifiers. Surface rod conversion kits exist precisely because moving in the other direction, towards exposed rods, is something you can do on site.

What Does LBR Mean and When Is It Used?

LBR stands for less bottom rod. The device is supplied without the bottom rod and bottom latch, so it latches only at the head.

The reason is the environment at the sill. A bottom latch sits where mop water, grit and floor dirt accumulate, and on a busy opening it is the component that stops working first. Removing it removes the problem.

LBR is common on fire rated openings, where the device still has to latch positively, but the designers would rather put all of that responsibility on the top latch than risk a bottom latch that is fouled with dirt. Where a bottom rod is removed, the configuration has to be the one the manufacturer intends, not simply the original device with parts left off.

Identifying an LBR device

Look at the bottom of the door. If there is no latch emerging from the bottom edge and no strike in the threshold, the device is either LBR or the bottom components have been removed by someone. Those are very different situations, and the door schedule is the way to tell them apart.

What Fails on a Concealed Vertical Rod Device?

The failures are consistent across manufacturers because the mechanism is the same shape everywhere.

How Do You Adjust Vertical Rods?

Adjustment is about travel, not about tension. The rod has to retract the latch far enough to clear the strike when the touchpad is pressed, and it has to let the latch return fully when the touchpad is released.

Work with the door open first so you can see what the latches are doing without the frame in the way. Press the touchpad, confirm that both latches retract fully, then release and confirm both return fully. A latch that returns sluggishly will not engage a strike reliably.

Then close the door slowly and watch where each latch meets its strike. If a latch is arriving high, low or off to one side, the strike is the thing to move, not the rod.

Why the door closer gets blamed and sometimes deserves it

A CVR device needs a positive push at the very end of the swing to drive both latches home. If the closer has lost its latch speed, the door drifts into the frame and the latches do not engage.

That presents as a device fault and is not one. Before stripping the device, check the closer. Our guide to adjusting a commercial door closer covers the latch valve, which is the adjustment that matters here.

What Changes on a Fire Rated CVR Device?

Fire rated configurations behave differently in two ways that matter every day.

Dogging is not available. A fire exit device may not be held in the retracted position, because the door has to latch every time it closes. If a device on a fire door has a dogging keyhole, something is wrong with how the opening was specified.

Latching has to be positive. The door has to actively latch, not merely come to rest against the frame, which is why rod adjustment on a fire rated CVR device is a life safety matter rather than a convenience one.

Our commercial door fire rating guide and the NFPA 80 inspection guide cover what an inspection is looking for on these openings.

Which Parts Do You Order and What Do You Need to Know First?

Four pieces of information settle a CVR parts order, and three of them have to be read off the door rather than guessed.

For the model level breakdowns, our 9947 CVR parts guide and 9847 CVR parts guide list the components by assembly, and the exit device parts section covers the wider range.

If you are still deciding between device types rather than repairing one, our exit device and panic bar comparison and the Von Duprin series comparison cover the choice, and panic hardware on commercial doors covers where the code requires a device at all.

About the Author

Security Parts has supplied repair parts for commercial door hardware since 2001, covering Von Duprin, LCN, Schlage, Falcon, Detex and Adams Rite at the component level. Our diagram based lookup exists so a technician can confirm a part before ordering it. This guide was written by the Security Parts team from supplier documentation and the questions our customers bring us.

If the device stamping is hidden under the cover and you would rather not pull the door apart to find it, contact us with a photograph of the device and the door, and we will narrow it down before you order.

Quick Summary

Parallel arm is the mounting most people have seen the most and named the least. It is the flat looking arm tucked up against the door face in corridors, schools and hospitals, chosen because nothing sticks out into the space where people walk.

This guide covers how parallel arm mounting differs from the alternatives, why it changes the spring size you need, what the shoe is doing, and which parts to order when something on the arm side fails.

What Is a Parallel Arm Door Closer?

A parallel arm door closer is a surface closer mounted on the push side of the door, with the closer body fixed to the door leaf and the arm running back parallel to the face of the door to a shoe mounted on the underside of the frame head.

The name describes the arm, not the closer. When the door is closed, the arm lies flat along the door rather than standing out at an angle, which is the whole point of the arrangement.

Almost every common surface closer can be mounted in all three positions. What changes is the arm, the shoe and sometimes a bracket or plate, so converting a door from one mounting to another rarely means a new closer.

Parallel Arm, Regular Arm or Top Jamb: How Do the Three Mountings Differ?

The differences come down to which side of the door the closer lives on and where the load is transferred.

Regular arm puts the closer on the pull side of the door, with the arm reaching up to the soffit of the frame. It is the most mechanically efficient arrangement, and it is the one where the arm is most exposed, because it projects out from the door.

Top jamb puts the closer on the frame rather than the door, on the push side. It is used where the door leaf cannot take the closer body, for example on a narrow stile aluminium door, or where the door is a pair of glazed leaves.

Parallel arm puts the closer on the door on the push side, with the arm folded back. It gives the cleanest result in a corridor and it protects the arm, at the cost of efficiency.

Why Does Parallel Arm Mounting Need More Spring Power?

This is the part that surprises people. A door that works perfectly on regular arm mounting can feel weak and fail to latch when the same closer is moved to parallel arm.

The reason is leverage. In parallel arm mounting the arm works at a less favourable angle through most of the swing, so less of the closer spring energy reaches the door as closing force. The closer has not changed. The geometry has.

In practical terms that means you plan for a higher spring setting on a parallel arm installation than you would on the same door with regular arm mounting, and you check that the door still latches under the conditions it actually sees.

That third row is the tension to be aware of. Accessible openings cap the force needed to open an interior hinged door, and parallel arm mounting pushes the spring setting the other way. Where both requirements bite, the answer is usually a correctly sized closer rather than a compromise, and sometimes a power operator. Our closer sizing guide covers how the sizes map to door width and weight.

When Should You Choose Parallel Arm?

Four situations point strongly at parallel arm mounting.

The door opens into a circulation route. A projecting arm in a corridor is both a snag hazard and something people walk into, so folding it flat against the door removes the problem.

The opening sees abuse. Schools, hospitals, back of house areas and anywhere trolleys pass through all shorten the life of an exposed arm. A parallel arm sits out of the way.

The appearance matters. On a visible entrance the flat profile reads as tidier than an arm standing out at an angle.

A stop is needed and there is no room for a separate overhead stop. Parallel arm shoes are available with stop functions built in, which solves two problems with one part.

What Is the Shoe and Why Does It Matter?

The shoe is the bracket that fixes to the underside of the frame head and receives the forearm of the closer arm. On a parallel arm installation it is the part that makes the mounting what it is.

Two things follow from that. First, the shoe is a separate part, so a damaged shoe does not mean a new closer or even a new arm. Second, shoes are not universal, so the closer series has to be identified before ordering.

The shoe is also what carries the stop function on the variants that have one. The arm pushes against a built in stop inside the shoe at the end of the opening swing, so the shoe is doing structural work as well as locating the arm.

What Are Cush-N-Stop and Stop Arms?

These are parallel arm variants with a stop built into the shoe, so the door is prevented from opening past a set angle without a separate overhead stop or a floor stop.

A plain stop arm provides a hard stop. A cush arm cushions the end of the swing rather than stopping it abruptly. A spring cush arm adds a spring to absorb the energy of a door that is thrown open, which is the version specified where abuse is expected.

One caution. A stop built into the arm transfers the force of a door being thrown open into the closer and into its fixings. On a genuinely abusive opening a separate overhead stop alongside a plain arm is often the longer lasting arrangement.

What Is an Extra Duty Arm and When Do You Need One?

An extra duty arm is a heavier parallel arm built for openings where a standard arm will not survive. It is the answer to doors that get kicked, propped, pulled and generally mistreated.

The clue that you need one is the failure history. If the same opening has had arms replaced more than once, the fix is not another standard arm, it is a heavier one, and probably a look at whether the door has a stop at all.

Extra duty arms and stop arm variants are often specified together on the worst openings, because an abused door usually has both an arm problem and a swing control problem.

Do You Need a Mounting Plate or Bracket?

Often, yes, and it is the part most frequently left off an order.

A parallel arm installation sometimes needs a mounting plate to give the closer body something to fix to, particularly where the door construction will not take the fixings directly, or where an existing fixing pattern does not match the new closer.

Drop plates and brackets solve the related problem of frames with a narrow soffit, or doors with glazing stops in the way. These are stocked separately and are series specific like the shoe.

The practical rule when replacing a closer on an existing door is to confirm what is currently fixed to the door and frame before ordering, because the old plate may not suit the new closer and discovering that on site costs a return visit.

What Goes Wrong With Parallel Arm Installations?

The useful habit is to separate arm side problems from closer body problems before ordering anything. An arm, a shoe and a plate are inexpensive parts to change. Our LCN door closer parts guide breaks the assemblies down, and the guide to the four main types of commercial door closer covers where surface closers sit overall.

What Do You Need to Confirm Before Ordering an Arm?

If the closer is being replaced rather than repaired, confirm the size as well. Our LCN closer selection guide covers choosing the unit, installing a commercial door closer covers fitting it, and the door closer parts section covers the components.

About the Author

Security Parts has supplied repair parts for commercial door hardware since 2001, covering Von Duprin, LCN, Schlage, Falcon, Detex and Adams Rite at the component level. Our diagram based lookup exists so a technician can confirm a part before ordering it. This guide was written by the Security Parts team from supplier documentation and the questions our customers bring us.

To match an arm to the closer you already have, browse LCN parts or the door closer parts section, or contact us with the series stamping and we will confirm the arm, shoe and plate together.

Quick Summary

The 996L is one of those parts that is easy to order wrongly. The lever looks the same across the range, the escutcheon looks the same, and the difference between two part numbers can be a single letter that changes how the door behaves for everyone who uses it.

This guide sets out what each variant does, which device the trim has to match, and the four pieces of information that settle the order, so you can replace trim without changing the way the opening works.

What Is the Von Duprin 996L and What Does It Do?

The 996L is outside trim for an exit device. An exit device on its own handles one direction only: push the bar from the inside and the door opens. Trim is what gives you a controlled way back in from the outside.

It consists of an escutcheon plate, a lever and, in most functions, a cylinder that decides whether the lever is live. The trim does not latch the door itself. It reaches through to the device and operates the device latch.

That relationship is the thing to hold on to. If the lever turns freely and the door does not open, the problem is as likely to be in the device as in the trim, and swapping the trim will not fix it.

Which Exit Devices Does the 996L Trim Fit?

Trim is matched to the device family, not just to the door. The 996 range is the trim family used with Von Duprin exit devices, and the specific device series decides which variant of the trim is correct.

Before ordering, identify the device underneath. The series stamping, the chassis shape and the device configuration all feed into the trim choice, and a trim that physically mounts is not necessarily a trim that operates the latch correctly.

Our Von Duprin 98 and 99 Series parts guide and the Von Duprin series guide cover how to read the device before you look at trim at all.

What Do the 996L Suffixes Mean?

The base number tells you the family and the lever. Everything after it tells you the behaviour.

This is the single most common ordering mistake on trim. A 996L and a 996L-NL look almost identical on the door and behave completely differently for the person trying to get in, so a like for like replacement has to carry the suffix across.

Reading an existing trim

The suffix is not always stamped where you can see it. If the trim is already fitted and unmarked, work it out from behaviour instead: try the lever with the door unlocked, then with it locked, and see whether the key retracts the latch or merely changes what the lever does.

Why the suffix is a safety decision, not a preference

Changing the suffix changes who can get through the door. Replacing a night latch trim with a standard lever trim turns a key controlled service entrance into a door anyone can open by hand. Replacing a standard trim with dummy trim locks out people who are supposed to have access.

Because the hardware mounts identically, neither mistake announces itself during installation. It shows up later, as a security incident or as a complaint that a door no longer works. Confirm the function before the old trim comes off the door, not after.

How Does the 996L-NL Night Latch Version Behave?

On a night latch trim the lever is not a latch operator. It is a pull. The key is what retracts the device latch, and it does so only while it is turned.

That makes it the standard choice on doors where nobody should be able to walk in by turning a handle, but authorised staff need key access. Service entrances, delivery doors and back of house openings are the usual homes for it.

The failure mode people report is a night latch that stops retracting the latch. That usually points to the cylinder, the tailpiece length or the device, in that order, rather than to the trim body. Our 880 night latch trim guide covers the same function on a different trim family.

When Would You Use 996L-BE or 996L-DT?

These two look similar on paper and do different jobs.

The 996L-BE is blank escutcheon trim. There is no cylinder preparation, so there is no outside key access at all. It is used where the opening is controlled some other way, or where an outside key would create a security problem rather than solve one.

The 996L-DT is dummy trim. The lever does not operate anything. It exists to give a hand hold and to make a pair of doors look consistent, which is why it so often ends up on the inactive leaf.

What Is Key Capture Trim and Who Needs It?

Key capture trim holds the key while the trim is in the unlocked state. The key cannot be withdrawn until the trim is returned to locked, which means the person who unlocked the door cannot walk away and leave it unlocked without noticing.

Schools, shared buildings and any site where several people hold the same key are the places this earns its keep. It converts a procedural rule into a physical one.

If you already have standard 996L trim and want this behaviour, there is a stocked conversion kit rather than a requirement to buy complete new trim. That keeps the escutcheon, lever and finish you already have on the door.

What Is the M996 Motorized Trim and Can You Convert to It?

M996 is the motorized version of the same trim family. Instead of a cylinder deciding whether the lever is live, an electrical signal does, which is what lets the outside of an exit device join an access control system.

It is used where a card reader, a keypad or a scheduled unlock has to control entry while egress stays mechanical. The device still opens from the inside with a push, whatever the trim is doing.

Conversion is a stocked route. There is a kit specifically for taking 996 R, V and C function trim to M996 motorized, so an existing mechanical opening can be brought onto access control without replacing the device.

For how that fits into the wider system, see our access control hardware integration guide and the QEL conversion kit parts guide, which covers the equivalent change on the device side.

996L Lever or 996K Knob: Which Is Fitted and Which Should Be?

The same trim family exists with a knob, designated 996K. Mechanically the two do the same job. For accessibility they do not.

Hardware on an accessible route has to be operable with one hand without tight grasping or twisting of the wrist, and a knob cannot be turned without doing both. That is why a 996K on a main entrance tends to become a 996L after an accessibility review.

If the trim is being changed for that reason, the finish and the device series stay the same, so only the trim part number changes. The device, the cylinder and the strike can all stay where they are.

What Do You Need to Confirm Before Ordering 996L Trim?

Four pieces of information. Collect them at the door and the order becomes straightforward.

Cylinders are the fifth consideration, and they are usually ordered separately. Confirm whether the trim you are buying includes cylinder preparation, whether you are reusing an existing cylinder, and whether the keyway matches the rest of the site. Our mortise cylinder and rim cylinder guide covers which cylinder type belongs with which device.

What Fails on 996L Trim?

Trim failures are mechanical and predictable. The lever is the part that absorbs daily use, so it is the part that wears.

Start every one of these at the device rather than at the trim. The Von Duprin parts guide and the exit device parts section cover the components the trim is reaching through to.

Trim that was never right in the first place

Not every trim problem is wear. A proportion of the trim we are asked about was ordered as a visual match rather than a functional one, usually during a refurbishment where somebody matched the finish and the lever shape and did not check the suffix.

The clue is that the door has behaved the same way since the work was done. Wear comes on gradually, a wrong part is wrong from day one. If staff say the door has never worked properly since it was changed, check the function before you check for wear.

About the Author

Security Parts has supplied repair parts for commercial door hardware since 2001, covering Von Duprin, LCN, Schlage, Falcon, Detex and Adams Rite at the component level. Our diagram based lookup exists so a technician can confirm a part before ordering it. This guide was written by the Security Parts team from supplier documentation and the questions our customers bring us.

To see the trim variants side by side, start at the 996 trim range or browse Von Duprin parts. If you are not sure which function is on the door, contact us and describe how the lever and key behave.

Quick Summary

Any time an electrified lock, a latch retraction device or a monitoring switch goes on a door, somebody has to answer an awkward question: how does the wire get from a frame that never moves into a leaf that swings a few hundred times a day without breaking?

The electric hinge is one answer, and often the neatest one. This guide covers how it works, when it is the right route, how to size it, and why most problems with electrified doors turn out to live in this part of the system rather than in the lock.

What Is an Electric Hinge and What Problem Does It Solve?

An electric hinge is a door hinge with conductors built into it. Externally it looks like a normal butt hinge. Internally, a set of small wires passes through the knuckle, so the two leaves of the hinge are electrically connected as well as mechanically connected.

The problem it solves is flex. A cable stretched between a frame and a door would be bent through the same arc at the same point thousands of times, and copper that is flexed repeatedly at a single point eventually breaks. Routing the conductors through the pivot axis means they twist rather than bend sharply.

The second thing it solves is appearance and tamper resistance. There is nothing on the surface to cut, catch or paint around, which matters on public facing entrances and on doors where a visible loop would invite interference.

How Does an Electric Hinge Actually Carry Power?

The conductors leave the hinge through a small opening at the back of each leaf. One set goes into the frame, where it joins the wiring from the power supply and the access control panel. The other set goes into the door, where it runs through a raceway drilled inside the leaf to whatever device needs it.

Inside the knuckle the wires are arranged so that opening the door twists them gently along their own axis rather than folding them. That is the whole trick, and it is why a hinge route lasts where a casually routed cable does not.

The hinge is still a hinge

It is easy to treat an electric hinge as an electrical component that happens to be hinge shaped. It is not. It still carries the weight of the door, so it has to suit the door size, weight and frequency of use exactly as a plain hinge would.

If the opening has three hinges and one is swapped for an electric version, the other two have to be in good condition. A sagging door puts a shearing load through the knuckle, and that is precisely where the conductors are.

Electric Hinge, Power Transfer or Armored Loop: Which Route Should You Use?

All three move power from frame to door. They differ in how much current they will carry, how much preparation they need and how visible they are.

In practice the deciding question is what is at the far end. Monitoring switches and small solenoids are comfortable on a hinge. Motor driven devices usually push you towards a power transfer. Our electric power transfer guide covers that side in detail.

How Many Conductors Do You Need?

Count the devices in the door leaf first, then count the wires each one needs, then add spares. Counting devices and stopping there is how installers end up one pair short on the day.

Two rules keep people out of trouble. Always specify spare conductors, because adding a monitoring function later is cheap if the wires are there and expensive if they are not. And always check the inrush, not just the holding current, on anything with a motor in it.

What Hardware on the Door Actually Needs Power?

It helps to be precise about which side of the opening each device sits on, because only the devices in the moving leaf need the transfer route at all.

Electric strikes do not. A strike lives in the frame, so it is wired directly and needs no transfer. That single fact is why a strike is often chosen over an electrified lock when retrofitting an existing door.

Electromagnetic locks usually do not either, because the magnet mounts to the frame or header and only the armature plate goes on the door. Our electromagnetic lock parts guide covers the exceptions.

What does need the route is anything electrified inside the leaf: electrified lock bodies, electrified exit device trim, latch retraction devices, request to exit switches built into the device, and latch monitoring contacts. If you are weighing a door mounted option against a frame mounted one, our electrified mortise lock and electric strike comparison sets out the trade.

What Preparation Does the Door and Frame Need?

Three pieces of preparation have to line up, and all three have to be decided before anything is ordered.

The hinge mortise has to suit the hinge. Size, backset and screw pattern all follow the hinge model, and an electric hinge is not always dimensionally identical to the plain hinge it replaces.

The frame needs a route from the hinge pocket back to the point where the field wiring arrives. On a new frame this is designed in. On an existing frame it is often the hardest part of the job.

The door needs a raceway, a drilled path from the hinge pocket to the device location inside the leaf. On a hollow metal door this is factory work rather than site work, which is why electrified hardware is so much easier to specify at order time than to retrofit.

Weatherised and exposed openings

Exterior openings add a requirement the drawings often miss. Where the route is exposed, the cable itself needs protection against weather and against physical damage.

Does an Electric Hinge Work on a Fire Rated Door?

Fire rated openings can carry electrified hardware, but everything on the opening has to be compatible with the rating, and the hinge is part of the opening.

The constraints that matter are the ones that always matter on a fire door. The door has to self close and positively latch every time, and nothing fitted to the opening may prevent that. Hardware has to suit the rating of the assembly.

Practically, that means the fire rating of the assembly has to be checked against every component, the hinge included, before parts are chosen. Our commercial door fire rating guide covers how the labelling works and what it restricts.

Why Do Electric Hinges Fail, and What Does Failure Look Like?

Failures are almost always mechanical in origin even though they present electrically. The conductors are the thinnest part of the system and they live inside the part that moves.

That last row deserves attention. A route that reads perfectly on a continuity test can still fail under load, because a thin conductor drops voltage once current flows. Always measure at the device while it is working.

How Do You Troubleshoot a Dead Electrified Door?

Work from the power supply towards the device, and prove each stage before moving on.

Start at the supply and confirm the output under load, not at rest. Then confirm the signal is arriving at the frame side of the transfer route. Then check continuity across the transfer with the door closed, and again with the door open, because a fatigued conductor often reads fine in one position and open in the other.

Only when the transfer route is proven should the device itself be suspected. Our commercial door hardware troubleshooting guide covers the rest of the sequence, and the access control integration guide covers how the panel side should behave.

What Should You Confirm Before Ordering?

Get those six settled and the order is simple. Skip one and the usual outcome is a second visit, because transfer routes are not something you can change your mind about once the door has been cut.

About the Author

Security Parts has supplied repair parts for commercial door hardware since 2001, covering Von Duprin, LCN, Schlage, Falcon, Detex and Adams Rite at the component level. Our diagram based lookup exists so a technician can confirm a part before ordering it. This guide was written by the Security Parts team from supplier documentation and the questions our customers bring us.

To compare transfer options side by side, browse Detex parts and Von Duprin parts, or contact us with the device list and conductor count and we will confirm the route before you order.

Quick Summary

Most people meet ADA door clearance as a line on an inspection report rather than as a design decision. Somebody measures an opening, writes down a number that is short by an inch, and the building owner is left guessing whether that means a new door frame or a different part.

In practice the answer is usually a part. This guide walks through each clearance requirement in turn, explains what is actually being measured, and shows which piece of door hardware controls it, so you can work out whether the opening needs a carpenter or a box from the shelf.

What Does ADA Door Clearance Actually Mean?

ADA door clearance is shorthand for a group of requirements in the 2010 ADA Standards for Accessible Design that together make a doorway usable by someone with limited mobility, limited reach or limited grip strength.

The requirements fall into two families. The first is about space: how wide the opening is and how much floor there is to maneuver on either side. The second is about effort: how hard the door is to pull, how fast it comes back, and whether the handle can be worked with a closed fist.

The split matters because the two families have very different remedies. Space problems are building problems. Effort problems are hardware problems, and hardware problems are the ones you can usually solve without touching the structure.

Which doors have to comply?

Accessible routes are the trigger. Doors on an accessible route into and through a building have to meet these requirements, which in most commercial buildings means the main entrance, corridor doors, restroom doors and the doors to any space the public or employees are expected to reach.

Doors that are not on an accessible route, such as a door to a space entered only for maintenance, are treated differently. Local code and the building official have the final word, so confirm the scope before you start replacing parts.

How Much Clear Width Does an Accessible Door Need?

The standard calls for a minimum of 32 inches of clear width. The measurement is taken with the door open 90 degrees, from the face of the door to the opposite stop. It is not the width of the frame and it is not the width of the leaf.

That distinction catches people out. A 36 inch leaf does not give you a 36 inch opening, because the thickness of the door and the depth of the stop both eat into the gap. A 32 inch leaf will not pass at all.

Hardware can eat into it too. Door mounted projections between 34 and 80 inches above the floor are limited to 4 inches of projection into the opening, which is why surface mounted exit device chassis and bulky pull trim get looked at closely on narrow leaves.

Doors in series

Vestibules have their own rule. Where two doors are in series, there has to be at least 48 inches between them, measured clear of the swing of any door that opens into the space. A tight vestibule with two inward swinging doors is one of the most common failures on older buildings.

What Maneuvering Clearance Is Required on Each Side of the Door?

Clear width gets a person through the gap. Maneuvering clearance gives them the floor space to position a wheelchair, reach the handle and pull the door without being pushed backwards by it.

The required space changes with the direction of approach and with which side of the door you are on. The pull side always needs more room than the push side, because the user has to retreat as the door comes towards them.

That bottom row is the one that surprises facilities teams. Adding a door closer to a door that already has a latch changes the maneuvering clearance requirement on the push side. A closer is not a neutral addition to an opening.

Hinge side and latch side approaches have their own figures, and they are more generous in depth because the user is coming at the door from an angle. If an opening fails on approach geometry and the walls cannot move, a power operator is usually the way out.

How Much Force Can It Take to Open the Door?

Interior hinged doors are limited to 5 pounds of opening force. Sliding and folding doors carry the same 5 pound limit. The figure applies to the effort needed to get the door moving and to keep it swinging, not to the effort needed to release a latch.

Exterior doors are the exception people misquote. The ADA Standards do not set a maximum opening force for exterior hinged doors, which is why wind load and stack pressure are handled through local code and through the choice of closer rather than through a single national number.

Fire doors are the other exception. A fire rated door has to latch positively every time, which takes spring power, so the standard allows the minimum opening force permitted by the authority having jurisdiction rather than a flat 5 pounds.

Why the closer is almost always the cause

A door closer works by compressing a spring as the door opens. The stronger the spring setting, the harder the pull. Facilities teams raise the spring power to make a door latch reliably, then fail the opening force test without realising the two are connected.

The honest fix is rarely to weaken the spring until the door stops latching. It is to reduce the resistance the spring is fighting: free up a binding hinge, correct a dragging sweep, fix a strike that the latch is scraping into, and only then reset the spring.

How Slowly Does the Door Have to Close?

Closing speed is specified as a minimum time, which trips people up because every other door requirement is a maximum. The door has to take at least 5 seconds to travel from 90 degrees open down to 12 degrees from the latch.

Where spring hinges are used instead of a closer, the equivalent requirement is that the door takes at least 1.5 seconds to swing from 70 degrees to the closed position.

On a conventional closer this is the sweep valve, the adjustment that governs the main part of the swing. Latch speed, the short burst at the end, is a separate valve and is not what the 5 second measurement is testing.

If you are working through these valves on a specific unit, our guide to adjusting a commercial door closer walks through the order to do them in, and the closer sizing guide covers choosing the right size in the first place.

What Height Does the Door Hardware Have to Be?

Operable hardware has to sit between 34 and 48 inches above the finished floor. That band covers levers, panic bar touchpads, thumbturns and anything else a user has to work to get through the door.

Most commercial hardware lands inside the band by default, because standard lock heights put a lever at around 38 to 40 inches. The parts that drift outside it are additions: a surface bolt near the top of the door, a secondary deadbolt fitted high, or a thumbturn mounted above the main lock.

On a pair of doors, check the inactive leaf as well. Flush bolts at the head of the inactive leaf are not operable parts in the accessibility sense, but any hardware a user is expected to work to pass through the opening is.

Which Types of Door Hardware Meet the Operable Parts Rule?

The rule is written in terms of what the user must not have to do. Hardware must be operable with one hand and must not require tight grasping, tight pinching or twisting of the wrist. Operating force is capped at 5 pounds.

That wording is what rules out the round knob. A knob cannot be turned without grasping and twisting, and no amount of adjustment changes that. It also rules out small thumbturns that need a pinch grip, and tight recessed pulls.

Levers that have stopped behaving

A compliant lever that has worn is a quiet failure. Once the return spring weakens the lever droops, and a drooping lever is both a snag hazard and a sign the latch is no longer being fully retracted. Spring cages and lever kits are stocked as individual parts for exactly this reason.

When Does a Power Operator Become the Only Practical Answer?

Three situations push an opening towards a powered solution. The maneuvering clearance is not there and the walls cannot move. The door is a fire door that has to latch, so the spring power cannot come down. Or the door is an exterior door fighting wind and stack pressure.

Low energy operators are the type used on accessible entrances. They open the door slowly, under limited force, and only when a person deliberately activates them by pressing a plate or waving at a sensor. They are covered by ANSI/BHMA A156.19, which sets the opening and closing timings.

The operator is only half the decision. The activation device is a separate choice, and it has its own reach and height requirements because a user has to be able to work it from a clear floor space that does not sit in the path of the opening door.

For the whole powered opening, including sensors and control boxes, see our commercial door operators guide and the door operator parts guide.

What About Thresholds and the Bottom of the Door?

Thresholds at doorways are limited to half an inch in height. Anything above a quarter inch has to be beveled, at a slope no steeper than one in two, so a wheel can ride up rather than stop against a square edge.

The push side of the door has its own rule. The bottom 10 inches has to present a smooth surface across the full width, so a footrest can push the door open without catching. Projecting kick plate edges and applied mouldings in that zone are what fail this one.

Both of these are easy to break during a repair. A new sweep that stands proud, or a kick plate fitted with raised fixings, can put a previously compliant door outside the rule without anyone noticing.

Which Parts Do You Actually Change to Bring an Opening Into Compliance?

Working from the most common finding to the least, the fix list is short and almost all of it is parts rather than construction.

Before ordering anything, confirm what is already on the door. The closer body, the arm and the mounting plate are separate line items, and an arm change alone sometimes solves a force problem that looks like it needs a new closer. Our door closer parts section and the guide to the four types of commercial door closer cover how those pieces fit together.

Where the opening is also fire rated, check the two requirement sets together rather than one after the other. Our commercial door fire rating guide and the ANSI and BHMA standards guide explain where the grading and labelling requirements sit alongside accessibility.

About the Author

Security Parts has supplied repair parts for commercial door hardware since 2001, covering Von Duprin, LCN, Schlage, Falcon, Detex and Adams Rite at the component level. Our diagram based lookup exists so a technician can confirm a part before ordering it. This guide was written by the Security Parts team from supplier documentation and the questions our customers bring us.

If you have a measurement that is failing and you know the hardware on the door, start with the parts by product type index, or contact us with the model number and we will confirm the part before you order.

Quick Summary

Falcon hardware tends to turn up on a job without any paperwork. Somebody inherits a building, a lever snaps or a device stops dogging, and the only clue to what is installed is a stamping on the chassis and a shape that looks familiar.

This guide is the orientation layer. It covers which Falcon families exist, how to tell them apart on the door, how the service part numbering behaves, and which of our deeper part guides to go to once you know what you are holding.

What Is Falcon Door Hardware and Where Does It Sit?

Falcon is a commercial door hardware line covering exit devices, cylindrical locks, mortise locks and the cylinders and trim that serve them. It is specified where a building needs dependable, serviceable hardware without the weight and cost of the heaviest institutional ranges.

The practical consequence for a facilities team is that Falcon openings are repairable. The ranges were designed around replaceable sub assemblies rather than sealed units, so a failure usually resolves to one part rather than to a new lock.

That is also why identification matters more than it does on some ranges. The same lever can appear across several chassis, and the same looking exit device can be a 24 or a 25 depending on the stile it was built for.

Which Falcon Product Families Will You Find on a Commercial Door?

Four families account for nearly everything in service. Knowing which one you are looking at narrows the part search from thousands of numbers to a few dozen.

Exit devices

The 19 Series is the lighter of the three exit device ranges. The 24 Series is the heavy duty narrow stile device, built for aluminium and glass openings where there is very little stile to work with. The 25 Series is the heavy duty wide stile device used on hollow metal and wood doors.

Each of those series then carries configurations: rim, surface vertical rod, concealed vertical rod and mortise. The configuration decides which latching parts exist, so it has to be settled before any part is ordered. Our Falcon 19, 24 and 25 Series parts guide works through each one.

Cylindrical locks

The T Series is the Grade 1 cylindrical lockset. It is the family you meet on classroom and office doors, and the one whose spring cage becomes a talking point once levers start to sag. The Falcon T Series parts guide covers the function codes and chassis numbers.

Mortise locks

The M Series is the mortise family. Mortise locks carry their functions inside a single case set into the edge of the door, and the function is changed with cams and internal parts rather than by swapping the whole lock.

Cylinders, trim and keying parts

Cylinders sit across all three families. Deadbolt cylinders, keyed in lever kits and the tailpieces that connect a cylinder to a chassis are ordered separately from the locks themselves.

How Do You Tell Which Falcon Exit Device You Have?

Start with the door, not the device. The stile is the single most useful clue, because the narrow stile and wide stile ranges were built for different openings and rarely appear on the wrong one.

Next look at the rods. No rods at all means a rim device latching into a strike on the frame. Visible rods running up and down the face of the door mean surface vertical rod. No visible rods but latches top and bottom means concealed vertical rod, with the rods running inside the door.

Finally check the dogging. A hex dogging keyhole in the touchpad end tells you the device can be held in the retracted position, which in turn tells you it is not a fire rated configuration, because fire devices are not allowed to be dogged down.

What Is the Falcon T Series and How Is It Serviced?

The T Series is a cylindrical lockset, meaning the working parts sit in a chassis that passes through a bored hole in the door face, with the latch running into the edge.

Service on a cylindrical lock is mostly about three sub assemblies. The chassis carries the function. The spring cage returns the lever. The latch and strike decide whether the door actually stays shut.

The symptoms and what they point to

A lever that droops points at the spring cage. A lever that turns but does not retract the latch points at the chassis or the lever connection. A door that will not stay shut, with the lever behaving normally, points at the latch or at strike alignment rather than at the lock.

That last one is worth separating out, because a misaligned strike gets blamed on the lock more often than anything else. Our cylindrical lock parts guide covers how the pieces relate.

What Does the Falcon M Series Cover?

The M Series is the mortise range. A mortise lock case is let into a pocket cut in the edge of the door, which gives it room for more internal mechanism than a cylindrical lock has.

That extra room is why mortise locks carry the more complex functions, and why the cam becomes an ordering decision. Cams translate the turn of the cylinder into movement inside the case, and different functions take different cams.

If you are working on the mortise case itself rather than the cylinder side, the mortise lock parts guide covers the internal components, and commercial lock function codes explains how the function designations are read.

How Do Falcon Service Part Numbers Work?

Falcon service parts do not all share one numbering scheme. They carry prefixes that group parts by the family they serve, and recognising the prefix tells you which family you are in before you read the rest of the number.

The lesson is simple. A partial number is not enough. The suffix after the prefix usually carries the finish, the pin count or the specific variant, and two parts that differ only in the last three digits can be completely different items.

Which Falcon Parts Fail First?

Across the families the failures cluster into a short list, and most of them are wear items rather than defects.

The pattern is that a Falcon problem is usually a sub assembly problem. Before ordering a complete lock or device, confirm which of these the symptom actually matches.

Can You Mix Falcon Parts With Other Hardware on the Same Door?

Within the cylinder and keying world, yes, and the catalogue reflects it. There are tailpieces and keyed in lever kits made specifically so a Falcon cylinder can serve a lever or chassis from another range in the same family of brands.

That is a deliberate convenience rather than an accident, and it is why you will find parts described as a Falcon tailpiece or a keyed in lever for a Falcon cylinder sitting under a different brand name in the parts list. The cylinder dictates the keyway, the tailpiece dictates the fit.

Outside of cylinders and keying, mixing is a different matter. Chassis parts, latch assemblies, rods and dogging components are family specific, and a part from one exit device series will not serve another even where it looks similar.

How Do You Confirm a Falcon Part Before You Order It?

Four pieces of information settle almost every Falcon order. Collect them before you search.

Fire rated openings add one more step. Confirm the rating from the label on the door edge, because fire configurations exclude dogging and insist on positive latching, and those two facts rule several otherwise identical parts out.

Where to Start for Each Falcon Family

Once you know the family, go straight to the part level rather than browsing. The Falcon replacement parts section is the starting point, and the family guides go deeper.

For egress hardware, use the 19, 24 and 25 Series parts guide alongside the exit device parts section. For cylindrical locks, the T Series guide and the cylindrical lock parts section. For deadbolt cylinders and keying parts, the Q500 parts guide and the deadlock parts section.

If you have a Falcon part number already, the parts by brand index and the full products and parts index will take you to the item directly.

About the Author

Security Parts has supplied repair parts for commercial door hardware since 2001, covering Von Duprin, LCN, Schlage, Falcon, Detex and Adams Rite at the component level. Our diagram based lookup exists so a technician can confirm a part before ordering it. This guide was written by the Security Parts team from supplier documentation and the questions our customers bring us.

If the stamping on the device is unreadable or the series is not obvious, contact us with a photograph of the chassis and the door type, and we will confirm the family before you order.

Quick Summary

A strike plate costs a fraction of what the lock costs and decides whether the lock works. It is also the part most likely to have been replaced by whatever was in the van, which is why so many doors have a strike that nearly fits.

This guide covers what the strike does, the types you will meet, how to work out which one an opening needs, and why most strike problems are not actually the strike. For the part level breakdown, see our strike plates and deadlatches parts guide.

What Is a Strike Plate and What Does It Do?

The strike plate is the metal plate fitted into the frame opposite the lock. It has an opening in it that the latch bolt or deadbolt enters when the door closes, and it is screwed into the jamb so that it sits flush with the frame face.

It does three jobs at once.

• It guides the latch. As the door swings closed, the sloped face of the latch runs along the lip of the strike and is pushed back into the lock. When it reaches the opening, it springs out again and the door is latched.
• It takes the load. Everything the door does, every slam, every pull against the lock, every attempt to force it, lands on the strike and its screws.
• It protects the frame. Without a plate, the latch would be hammering wood or thin steel on every cycle.

That first job explains why the lip exists and why its length matters so much.

What Is the Lip on a Strike Plate and Why Does Length Matter?

The lip is the curved tab that extends from the faceplate out over the edge of the frame. It is the ramp that pushes the latch back as the door closes.

Lip length is measured from the centre line of the strike to the end of the lip, and it is not a style choice. It has to be long enough that the latch meets it rather than meeting the frame or the architrave, and short enough that it does not project into the opening where people walk past it.

Get it too short and the latch catches on the frame edge instead of riding over the lip, so the door bangs rather than closing. Get it too long and the lip sticks out into the traffic, snags clothing, and gets bent by trolleys until it no longer guides anything.

This is why you will see the same strike offered in a range of lip lengths as separate part numbers. A T shaped square corner strike with a plastic box might be stocked in half a dozen lip lengths, and they are not interchangeable once the frame is built.

What Are the Different Types of Strike Plate?

These are not interchangeable. The frame has been prepared for one shape, and fitting a different one means either a visible gap or cutting the frame. On a rated opening, cutting the frame is not a casual decision at all.

The ANSI pattern is the one worth knowing because it is the common denominator. A frame prepped to the ANSI strike pattern will take any strike built to it, which is precisely the point of having a standard.

Does the Box Behind the Strike Matter?

Yes, more than most people expect.

Behind the opening in the strike there is a cavity in the frame. A box, sometimes called a dust box, lines that cavity. Its obvious job is keeping mortar, insulation and debris out of the space the latch has to enter, because a latch that cannot fully extend is a latch that can be pushed back.

Its less obvious job is resistance. Strikes are stocked both with plastic boxes and with metal boxes, and that is a deliberate difference. A plastic box is fine on an interior door where nothing is going to be attacked. On an exterior door or anything protecting value, a metal box adds real resistance behind the plate rather than just keeping the hole tidy.

When you order a strike, check whether the box is included and which kind it is. The part number usually tells you.

Why Will My Door Not Latch? Strike Alignment Explained

This is the complaint behind most strike work, and the first test takes ten seconds.

Open the door and operate the latch by hand. If the latch extends and retracts freely with the door open, the lock is fine. The problem is between the latch and the strike. If it binds with the door open, the problem is in the lock or the door prep and the strike is innocent.

Assuming the lock is fine, there are three ways the alignment can be out.

The marks tell you the direction. A strike face with a bright wear line above the opening is a door that has dropped, and the fix is at the hinges, not at the strike. Filing the strike opening bigger to accommodate a sagging door is the repair that comes back.

When Moving the Strike Is the Right Answer

Sometimes it genuinely is. Frames settle, buildings move, and a strike fitted square to a frame thirty years ago may no longer be square to the door. In that case the strike is relocated properly, with the old fixing holes filled so the new screws bite into solid material rather than spinning in enlarged holes.

What is not a repair is packing the strike out with washers, or enlarging the opening with a file until the latch finds its way in. Both work for a while and both leave an opening that is easier to force than it was.

What Is a Rabbeted Strike and When Do You Need One?

A rabbeted frame has the door stop formed as a step in the frame section rather than planted on as a separate strip. The door sits into that step when it closes.

A flat strike cannot follow that profile. Fitted into a rabbeted frame it either stands proud of the step or leaves the latch meeting a corner, and neither works. A rabbeted strike is stepped to match, so its face follows the frame and the latch meets a continuous surface.

You can identify a rabbeted frame in a second by looking at the jamb with the door open. If the stop is a separate piece of timber or steel pinned on, the frame is not rabbeted. If the stop is part of the same section, stepping back from the face, it is.

Getting this wrong is common on replacements, because a flat strike will physically screw into a rabbeted frame. It just will not latch reliably, and the symptom looks like an alignment fault rather than the wrong part.

Why the Screws Matter as Much as the Plate

A strike is only as good as what is holding it in, and this is where most of the real security is won or lost on an exterior door.

Short screws reach into the frame skin and nothing else. Under a kick, the screws tear through thin material and the whole strike comes away with a section of jamb, regardless of how strong the lock was. Longer fixings that reach past the frame into the structure behind change what has to fail before the door opens.

Three things worth checking on any strike you are working on:

• Are the existing holes still sound, or have they been enlarged by previous adjustment so the screws no longer bite.
• Is the strike sitting flat, or has it been packed out with washers to cover an alignment problem.
• Is the frame reinforced behind the strike, which on hollow metal usually means a strike reinforcement rather than bare skin.

None of that is expensive. All of it is invisible once the door is shut, which is why it gets skipped.

What Should You Check on a Strike During Routine Maintenance?

1. Look for wear marks on the strike face, which show the latch is not arriving where it should.
2. Check the lip is straight and has not been bent by trolleys or carts.
3. Test the latch from a slow close, not a slam, because a slammed door will latch over a fault that a gentle close will not.
4. Check the deadlatch lands on the strike face, not in the opening, on locks that have one.
5. Check the screws are tight and that the holes have not opened up.
6. Look into the box for debris, particularly on doors near building work.

The slow close test is the useful one. Most doors that have a developing strike problem will still latch if you let them slam, so a quick check during a walk round misses it. Close the door gently and see whether it latches on its own.

Strikes, Deadlatches and Electric Strikes

Three things get called strikes and they are not the same.

• A strike plate is passive. It is a shaped piece of metal with no moving parts.
• A deadlatch is part of the lock, not the frame. It is the small plunger beside the main latch that stops the latch being pushed back once the door is closed. If the deadlatch misses the strike face it is not doing its job, which is another reason strike alignment matters.
• An electric strike replaces the passive plate with a powered one that can release the latch on a signal. That is a different product with wiring, handing and fail safe or fail secure behaviour to decide.

For the powered version, see our electric strike schematic diagram and the electric strike parts section.

What to Confirm Before Ordering a Strike Plate

1. The frame prep, which decides the shape: ANSI, square corner, T or rabbeted.
2. Faceplate dimensions, measured off the existing plate.
3. Lip length, measured from the centre line to the end of the lip.
4. Whether a box is included, and whether it should be plastic or metal.
5. What the strike has to receive, a latch bolt, a deadbolt, or both.
6. The finish, matched to the rest of the hardware on the opening.

Browse cylindrical lock parts and mortise lock parts for the locks these strikes serve, or the full products and parts index if you already have a part number.

About the Author

Security Parts has supplied repair parts for commercial door hardware since 2001, covering Von Duprin, LCN, Schlage, Falcon, Detex and Adams Rite at the component level. Our diagram based lookup exists so a technician can confirm a part before ordering it. This guide was written by the Security Parts team from supplier documentation and the questions our customers bring us.

For related reading, see our commercial door hardware troubleshooting guide and the commercial door hardware finish guide.

Quick Summary

The reader is the part of an access control system everybody sees and the part that does the least thinking. Understanding that split explains most of what is confusing about specifying one.

This guide covers what a proximity reader actually does, how mounting and technology are separate decisions, and what to confirm before ordering. For how the reader fits into the rest of the opening, see our access control and door hardware integration guide.

How Does a Proximity Card Reader Work?

A proximity reader emits a field. When a card or fob enters that field, the credential draws enough energy from it to power itself and transmit its number back. The reader picks up that number and passes it on.

Two things follow from that and both matter in practice.

First, the credential has no battery. It is powered entirely by the reader's field, which is why a card works for years and why it stops working at a distance. Range is a property of the field, not of the card.

Second, the reader is not making a decision. It reads a number and sends it to the controller. The controller holds the list of who is permitted, checks the number against it, and decides whether to release the door. If the door does not open, the reader is usually not the thing that refused.

Mullion, Wall or Mini: Why Mounting Decides the Part

Readers performing the same function come in different bodies, and the body is chosen by where it has to live.

Mullion readers exist because storefront doors leave almost nowhere to put anything. The mullion between the leaves is often the only vertical surface near the handle, and it is narrow, so the reader is built to match.

This is also why ordering goes wrong. The technology is identical across several of these, so somebody orders the wrong body and it physically will not fit the only place it can go.

What Is a Multi Technology Reader and Why Does It Matter?

Card technologies are not one thing. Older proximity formats, smart card formats and various proprietary schemes all exist in the same buildings, usually because the estate was built over decades.

A multi technology reader accepts more than one of those formats at the same reader. That turns an impossible migration into a manageable one.

Without it, changing credential technology means changing every reader and every card on the same weekend, because a reader that only understands the old format cannot read a new card and vice versa. With multi technology readers, you change the readers first, keep issuing old cards while both work, then switch credentials at your own pace and turn the old format off at the end.

That is why multi technology units dominate current ranges, and why the stocked line includes plain multi technology readers, keypad versions, mullion and wall bodies, and government specification variants built to federal credential requirements.

Reader Modules Versus Finished Readers

Some products in the range are described as reader modules rather than readers. A module is the reading electronics intended to be built into another assembly, rather than a finished unit with its own housing. If you are replacing something on a wall, you want the finished reader. If you are servicing an integrated product, you may want the module.

How Do You Change Which Card Technologies a Reader Accepts?

This is the part most people do not know exists, and it saves a surprising amount of trouble.

On multi technology readers, the set of card formats the reader will accept is configurable. Rather than returning the unit or editing anything in software, the change is made by presenting a configuration card to the reader.

The stocked range includes cards that enable all proximity card technologies, cards that disable all of them, and cards that turn individual technologies on or off one at a time. There are also configuration cards covering card serial number bit lengths.

Why that matters: a reader that accepts every format it can is convenient and is also reading credentials you may not want accepted. Turning off the technologies a site does not use narrows what will open the door. It also stops a reader responding to a visitor's card from an unrelated system, which is the sort of thing that generates confusing access logs rather than a real breach.

Keep the configuration cards with the site records. They are small, they look like ordinary cards, and a reader that has been reconfigured by somebody who then left is a puzzle nobody enjoys.

When Should a Reader Have a Keypad?

A card on its own is something you have. Anyone holding the card is treated as the person it belongs to, which is fine for most doors and inadequate for some.

Adding a keypad adds something you know. The user presents a credential and enters a PIN, so a lost or borrowed card is not enough on its own. Most ranges offer a keypad version of the same reader body, so the decision does not change the mounting.

Where that is usually worth it:

• Server rooms, comms rooms and plant spaces.
• Cash handling and stock rooms.
• Doors that are rarely used, where a missing card may not be noticed for weeks.
• Out of hours access on a door that is open to card only during the day.

Where it usually is not: high traffic main entrances, where a PIN at every entry creates a queue and encourages people to hold the door for each other, which defeats the whole arrangement.

What Does a Reader Need to Be Wired To?

A reader needs power and a data path back to the controller, and in most installations those run in the same multi conductor cable.

Three practical points come up on nearly every job.

• Metal affects range. Mounting a reader directly on a metal mullion or frame changes its field. Readers intended for mullion mounting are designed with that in mind, which is another reason to use the right body rather than the one that fits.
• Cable runs have limits. Readers are rated for a maximum distance to the controller, and exceeding it causes intermittent reads that look like a faulty reader.
• Keep reader cable away from lock power. The lock circuit switches a relatively large current, and running it alongside the reader data pair is a reliable way to create faults that come and go.

The lock itself is a separate decision from the reader. For what releases the door once the controller says yes, see our comparison of an electrified mortise lock versus an electric strike and our electromagnetic lock parts guide.

Why Reader Covers Are Ordered Separately

On several readers the outer cover is a separate part number with its own colour, and this catches people out on a replacement.

The stocked covers come in a range that includes black, cream, warm tone brown and cool tone gray, and they are specific to the reader body and gang size. A single gang cover is not a double gang cover, and a cover for one reader family will not clip onto another.

Two situations where this matters. The first is damage: a cracked cover does not mean a new reader, it means a cover. The second is appearance: a reader replaced like for like in function can look wrong on the wall if the cover colour was chosen to match a previous decor scheme.

When ordering a reader for an existing location, confirm whether the cover is included or separate, and record the colour from the one already on the wall.

What Goes Wrong With Card Readers?

The second row is the one worth internalising. A reader that beeps and flashes has done its job. If the door did not open, the problem is downstream of the reader, and replacing the reader will change nothing.

The Reader Is Only Half of a Monitored Door

A reader tells the system somebody presented a valid credential. It does not tell the system whether the door actually opened, whether it closed again, or whether somebody left through it.

That is the job of two other devices. A door position switch reports whether the leaf is open or closed. A request to exit device reports that somebody on the inside operated the hardware to leave. Without those, an access control system knows who was granted access and nothing about what happened next.

Our guide to request to exit and door position switches covers both and how they are wired.

What to Confirm Before Ordering a Reader

1. The mounting position, which decides the body: mini mullion, mullion, wall or keypad.
2. The card technologies in use on site, and any migration planned.
3. Whether a keypad is needed for that specific door.
4. Any government or federal credential requirement, which is a distinct product variant.
5. The interface and cable run back to the controller.
6. The finish and cover, which on several readers is a separately ordered part.

Browse Schlage parts for readers, modules, covers and configuration cards, or the full products and parts index if you already have a part number.

About the Author

Security Parts has supplied repair parts for commercial door hardware since 2001, covering Von Duprin, LCN, Schlage, Falcon, Detex and Adams Rite at the component level. Our diagram based lookup exists so a technician can confirm a part before ordering it. This guide was written by the Security Parts team from supplier documentation and the questions our customers bring us.

For the rest of the electrified opening, see our electric strike schematic diagram and the electric strike parts section.

Quick Summary

The double cylinder deadbolt is the most argued about piece of hardware in a commercial building. It solves one real problem and creates a different one, and which of those matters more depends entirely on the door it is going on.

This guide covers how it differs mechanically, where it is genuinely appropriate, where it is restricted, and what you need to know before ordering parts. For the components of the lock itself, see our deadbolt parts guide.

What Is a Double Cylinder Deadbolt?

A deadbolt is a bolt with no spring in it. It does not retract when the door closes against the frame, and it cannot be pushed back by pressure on the end. The only way it moves is because something turns it. That is what makes it a deadbolt rather than a latch.

What varies is what does the turning. On a single cylinder deadbolt there is a keyed cylinder on the outside and a thumbturn on the inside. On a double cylinder deadbolt there is a keyed cylinder on both sides, so the bolt cannot be operated from either face without a key.

Everything else about the lock is the same. The bolt, the strike, the backset and the door prep do not change. What changes is the inside trim and therefore the behaviour of the door from the inside.

Why Would Anybody Fit a Double Cylinder Deadbolt?

One reason dominates: adjacent glass.

If there is a glazed panel in the door or a sidelight next to it, a thumbturn on the inside is reachable. Break the glass, put an arm through, turn the thumbturn, open the door. The lock has been defeated without any attack on the lock at all.

A double cylinder deadbolt removes that route, because reaching the inside face achieves nothing without a key. That is a genuine security improvement on storefront doors, rear doors with glazed panels, and any opening where the glazing was designed before anybody thought about the lock.

Secondary reasons come up too. Doors that lead to a secured area from inside the building, where you want the door controlled in both directions. Store rooms inside a public space. Doors where the occupant should not be able to unlock the way out casually.

Where Are Double Cylinder Deadbolts Restricted?

The objection is simple and it is about getting out, not getting in.

If the only way to unlock a door from the inside is with a key, then anyone inside without the key is held in. In an ordinary day that is an inconvenience. In a fire, with smoke and no light, somebody hunting for a key at a door they need to be through is a serious problem.

That is why free egress is a principle that runs through commercial door hardware. A person should be able to leave through an exit with one motion, without a key, without special knowledge and without tools. A double cylinder deadbolt is in direct conflict with that on any door used for egress.

The practical rules vary by jurisdiction and by occupancy, and your authority having jurisdiction is the one that settles it for a given building. What is consistent is the direction of travel: the more a door is relied on as a way out, the less acceptable a key operated inside becomes.

The Compromise Nobody Should Use

A habit exists of fitting a double cylinder deadbolt and leaving a key permanently in the inside cylinder during occupied hours. It defeats the purpose in both directions. During the day the lock is a single cylinder with a key sticking out of it, and the glass attack it was fitted to prevent now works again. At night, if the key is removed and somebody is still inside, you have the egress problem in full.

If egress is required, the answer is different hardware for that opening, not a procedure that depends on somebody remembering.

What Should You Use Instead on an Exit Door?

Classroom function is worth understanding properly, because it answers a different question from the deadbolt. Our classroom deadbolt guide covers the function and the cylinder options, and our exit device parts section covers the panic hardware route.

Does the Grade of the Deadbolt Change the Single Versus Double Decision?

No, but it changes how much the decision is worth.

Deadbolts are graded, and the grade describes how much abuse the lock will take before it fails. Within the Schlage B range, the B600 series is the Grade 1 family and the B500 series sits below it. Both are available in single and double cylinder versions, so grade and cylinder count are two separate choices made at the same time.

The point worth making on a glazed door is that upgrading the grade does nothing about the glass. A Grade 1 deadbolt with a thumbturn inside is defeated through a broken pane exactly as fast as a Grade 2 one.

Grade protects against force applied to the lock. Cylinder count protects against somebody reaching the inside. They answer different attacks, so the right choice depends on which attack the door is actually exposed to.

The Bolt and the Strike Have to Match the Ambition

A heavy deadbolt in a light frame moves the weak point rather than removing it. If the bolt is strong and well thrown but the strike is screwed into a thin jamb with short screws, the frame fails first. On an exterior door where the deadbolt is doing real work, the strike and its fixings deserve the same attention as the lock.

What Goes Wrong With a Deadbolt?

Deadbolts have very few moving parts, so the failure list is short and most of it is alignment rather than the lock.

The pattern worth remembering is that a bolt which throws freely with the door open and binds with it closed is an alignment problem, not a lock problem. Replacing the deadbolt will not fix it. Our commercial door hardware troubleshooting guide covers the strike and frame side of the same complaint.

How Do You Tell Which One Is Fitted?

Look at the inside face. A thumbturn is a single cylinder. A keyway is a double cylinder. That is the whole test and it takes a second.

For ordering, you need more than that. In the Schlage B series, the single cylinder and double cylinder versions carry different model numbers, and the replacement cylinders are listed against those models. A cylinder listed for a B562 is not the same order line as one listed for a B662, even though both are deadbolt cylinders, because they belong to different grades within the range.

Each cylinder is also listed against a door thickness range. The same model will have one cylinder for doors from roughly one and three eighths to one and three quarters inches, and a longer one for thicker doors. Ordering without measuring is the fastest way to get a cylinder that will not reach or will not tighten.

Can You Convert a Single Cylinder Deadbolt to a Double?

Often yes, because the change is at the inside trim rather than in the door prep. The bolt, the case and the hole through the door are usually common to both.

What you are replacing is the thumbturn with a keyed cylinder, which means a cylinder of the correct length for the door and, if the building is keyed, one that matches the existing key system. Conversion and adapter kits exist for exactly this.

Before doing it, answer the egress question for that specific door. A conversion that is mechanically straightforward can still be the wrong decision, and it is far easier to decide that before the thumbturn comes off than after an inspection.

Keying a Double Cylinder Deadbolt Into the Building

Two cylinders means two cylinders to key, and on a building with an existing key system that is not a detail to leave to the installer on the day.

Both sides should normally be keyed alike to each other, so one key works from either face. Beyond that, the deadbolt has to sit correctly in the building hierarchy so the right master keys operate it. Our master key system design guide covers the levels of keying, and the Schlage key systems guide covers the keyways and cylinder formats.

What to Confirm Before Ordering

1. Single or double, confirmed by looking at the inside face.
2. The model number from the lock, because grades within a range take different cylinders.
3. Door thickness, measured rather than assumed.
4. The keyway and key system, so the new cylinder works with the existing keys.
5. The finish, matched to the rest of the hardware on the opening.
6. Whether the door is an exit, which may rule the double cylinder out entirely.

Browse deadbolt parts and diagrams for the exploded views, or the full products and parts index if you have a part number. Our Schlage B series deadbolt parts guide covers the range in detail, and the labelled deadbolt diagram names every component.

About the Author

Security Parts has supplied repair parts for commercial door hardware since 2001, covering Von Duprin, LCN, Schlage, Falcon, Detex and Adams Rite at the component level. Our diagram based lookup exists so a technician can confirm a part before ordering it. This guide was written by the Security Parts team from supplier documentation and the questions our customers bring us.

For related reading, see our comparison of a mortise cylinder and a rim cylinder and the thumbturn cylinder guide.

Quick Summary

Keyed alike is one of those phrases that gets used loosely, usually to mean "I want one key for everything". That is sometimes exactly right and sometimes the start of a problem that takes years to unpick. The difference is whether the group of doors will stay small and stable.

This guide covers what keyed alike actually is, how it differs from master keying, when it is the better answer and when it is not. For the hierarchical alternative, see our master key system design guide.

What Does Keyed Alike Mean?

Keyed alike means a set of locks has been pinned to accept the same key. Turn up with that key and every lock in the set opens. Turn up with any other key and none of them do.

Mechanically there is nothing clever about it. A pin tumbler cylinder is pinned so that one particular cut of key lifts its pins to the shear line. Pin a second cylinder the same way and it accepts the same key.

The locks need not be the same type, or even the same product. A deadbolt, a cylindrical lever lock and a padlock can all be keyed alike to each other provided they take compatible cylinders.

That last point is what people miss. Keying happens at the cylinder, not at the lock. The lock body determines the function, the cylinder determines the key.

How Is Keyed Alike Different From Master Keying?

They sound similar and they solve different problems.

Keyed alike is flat. There is one key and there are no levels. Everybody who holds it can open everything in the group, and nobody can be given access to part of it.

Master keying is hierarchical. Each lock keeps its own change key, and a higher level key is added that operates a defined set of locks. Each cylinder is pinned so that more than one key cut will reach the shear line.

A department head's key opens their floor, a facilities key opens more, and the grand master opens the building.

They are not mutually exclusive. A master keyed building will often have small keyed alike groups inside it, so that a row of identical store cupboards share one change key while still sitting under the building's masters.

When Is Keyed Alike the Right Choice?

It works well when three things are true: the group is small, everybody who needs one door needs all of them, and that is unlikely to change.

• A suite of rooms used by one team. Office, store, and the door between them.
• Multiple entrances serving the same people. Front, rear and side doors of one unit.
• Equipment and enclosures. Cabinets, gates and padlocks that the same maintenance person opens on the same round.
• Doors with two locks. A lever lock and a deadbolt on the same leaf should almost always be keyed alike, so one key does the door.

That last one is worth calling out because it is the most common sensible use. A door with a deadbolt above the lockset is two locks, and if they take different keys then every entry and exit is a two key operation that nobody thanks you for.

When Does Keyed Alike Become a Problem?

The failure mode is always the same: the group grew, or the people changed.

Keyed alike has no way to withdraw access from part of the group. If one person should no longer have the store room, you cannot take the store room off their key. You can only take the key, which removes everything, or rekey the store room, which separates it from the group permanently.

Lost keys are the second problem. One key opens everything in the set, so losing one exposes every door at once. The remedy is rekeying every cylinder in the group, and the larger the group has quietly grown, the more expensive that morning becomes.

The third is drift. Keyed alike groups are rarely designed. They accumulate. Somebody adds one more door "while we are here", and five years later there are forty cylinders on one key and nobody is sure which doors are on it. At that point the building needs a key system rather than a habit. Our Schlage key systems guide covers what a designed system looks like.

What Happens When You Need to Add a Door Later?

This is where keyed alike groups quietly go wrong, so it is worth planning for on day one.

Adding a door to an existing keyed alike group is easy if you know the key code. A cylinder is pinned to that code, fitted, and the existing key works. It takes minutes and costs very little.

It is a different job if nobody wrote the code down. Then you are either taking an existing cylinder apart to read the pinning, or cutting a new key from an existing one and working backwards. Both are achievable and both cost more than the five seconds it would have taken to record the code when the group was created.

What to Record

None of that needs software. A sheet of paper in the facilities file is enough, and it is the difference between a twenty minute job and a day.

How Do You Rekey a Keyed Alike Group?

The honest answer is that you rekey all of it or none of it, and that is the whole argument for keeping these groups small.

Because every cylinder accepts the same key, changing that key means changing every cylinder. Leaving one behind means the old key still opens one door, which is usually the door you were worried about.

Three routes, in order of how much they cost you.

1. Swap interchangeable cores. If the group is built on removable cores, a control key pulls each core and a pre pinned replacement goes in. Fastest by a wide margin.
2. Repin conventional cylinders. Each cylinder comes apart and is repinned to a new code. Reliable, but it is a visit to every door.
3. Replace cylinders entirely. Sometimes the quickest option when cylinders are worn anyway, or when the group is being redesigned rather than just rekeyed.

Whichever route, take the opportunity to write down the new code and the door list. The reason the group was painful to rekey is almost always that nobody did that last time.

Which Cylinders Can Be Keyed Alike?

Any set of cylinders that share a keyway and a compatible pinning can be keyed alike to each other. In practice that means three decisions.

Cylinder format being different is not an obstacle. A rim cylinder on an exit device and a mortise cylinder on a lock body are built completely differently, and both can be pinned to the same key. Our comparison of a mortise cylinder and a rim cylinder explains how the two differ physically.

Why Interchangeable Cores Change the Maths

On a conventional cylinder, rekeying means taking the cylinder apart and repinning it, which is a locksmith job done at the door or on a bench.

An interchangeable core system changes that. The core is removed as a unit with a control key and a new core goes in. Rekeying a door becomes a thirty second swap rather than a service visit, and the old core can be repinned elsewhere at leisure.

That matters most for exactly the situation where keyed alike goes wrong. If a key is lost on a twelve door keyed alike group, conventional cylinders mean twelve repinning jobs. Interchangeable cores mean twelve core swaps, which one person can do in an afternoon. Our master key system design guide covers the core formats and how they differ.

What to Confirm Before Ordering Keyed Alike Cylinders

1. Which doors are actually in the group, written down rather than assumed.
2. The keyway, so one blank fits everything.
3. Pin count, consistent across the group.
4. Cylinder format for each opening, rim, mortise, key in knob or key in lever.
5. Whether the building already has a key system this group has to sit inside.
6. How many keys are needed, and who will hold a record of them.

Browse Schlage parts for cylinders and cores, or the full products and parts index if you already have part numbers.

About the Author

Security Parts has supplied repair parts for commercial door hardware since 2001, covering Von Duprin, LCN, Schlage, Falcon, Detex and Adams Rite at the component level. Our diagram based lookup exists so a technician can confirm a part before ordering it. This guide was written by the Security Parts team from supplier documentation and the questions our customers bring us.

For related reading, see the thumbturn cylinder guide and our deadbolt parts and diagrams.

Quick Summary

An automatic door opener looks simple from the outside. Somebody presses a plate, the door swings, it closes again. Underneath there are four separate systems that have to agree with each other, and when one of them drifts the whole opening starts behaving strangely.

This guide covers how these systems fit together, the terminology that gets mixed up, and where the fault usually is when a powered door stops behaving. For the component level breakdown, see our door operator parts guide.

What Is an Automatic Door Opener and How Does It Work?

An automatic door opener, more properly called a door operator, is a powered unit mounted at the head of the opening that drives the door through its swing or slide. It replaces the push you would give the door yourself.

The important thing people miss is that the operator does not stop working once the door is open. It also controls the door coming back. A powered swing door still has to close at a controlled speed, latch properly, and not slam. So the operator contains or works alongside a closing mechanism, which is why the same manufacturers make both closers and operators and why the parts families overlap.

Operators are driven in different ways depending on the series. Some are electrohydraulic, some are pneumatic, and some are electromechanical. That difference decides what is inside the unit when it fails, and it decides which spares list you are working from.

Low Energy Versus Full Power

The term you will see constantly on accessible entrances is low energy. A low energy operator opens the door slowly and with limited force, and it is activated by a deliberate human action such as pressing a plate or waving at a sensor.

That is why low energy units can be used on an ordinary corridor or office door without a guard rail around them. Full power automatic doors, the sort that open as you walk at them, move faster and carry a different set of safety requirements. The products stocked for accessible entrances are explicitly described as low energy operators, supplied in single door, double door and dual egress versions.

Single, Double or Dual Egress: Why the Door Count Changes the Part

Operators are not ordered by the door, they are ordered by the opening. Three configurations come up and they are three different products.

Dual egress is the one that catches people out. The two leaves swing in opposite directions, usually in a corridor, so what looks like an ordinary pair is actually a different opening with its own part number. Confirm which of the three you have before ordering anything.

What Activates an Automatic Door Opener?

Activation is a completely separate decision from the operator, and this is where most of the product choice actually happens. The operator does not care what tells it to open, it just needs a signal.

• Push plates. The traditional answer. A square or round plate on the wall, usually carrying a wheelchair icon, wired back to the operator.
• Touchless actuators. The user waves a hand near the plate rather than pressing it. Stocked versions come in single gang and double gang sizes, with either a wave icon or a wheelchair icon and text.
• Bollard posts. A free standing post in the approach path, used where there is no wall in a sensible position. Available in flush length and full length versions.
• Wireless transmitters. Battery or mains actuators that signal the operator without a cable run, which is the practical answer in a retrofit where chasing a wall is not an option.

Why Bollards Exist

A push plate needs a wall. Plenty of accessible entrances have glass on both sides, a long approach across open paving, or a route where the nearest wall is too far from the door to be useful. A bollard puts the actuator where the user actually is.

Bollards are ordered as full length or flush length, and as actuator only posts or as complete actuator and bollard packages. Wireless bollard versions remove the cable run entirely, which on an existing paved approach is often the difference between a one day job and a week of groundwork.

How Do the Safety Sensors Keep the Door From Hitting Somebody?

A powered door that cannot see people is a hazard, so the safety layer is not optional and it is usually where intermittent faults live.

Two kinds of sensing are involved. Approach side sensing watches the area the door swings into. Door mounted sensing rides on the leaf itself and watches the space immediately in front of it as it travels.

Those two cannot both be active all the time, because a door mounted sensor sweeps a different area as the leaf moves and would see the floor, the frame or the wall. That is the job of the door position switch. A surface mount position switch disables the approach side sensor when the door is closed, working together with the door mounted safety sensor and a relay module, so the operator knows which part of its cycle it is in.

The practical consequence: when a powered door starts stalling, reopening for no reason, or refusing to settle, check the sensors and the position switch before condemning the operator. Our guide to actuators, sensors and accessories for automatic operators covers those components individually.

What Connects the Operator to the Door?

The operator drives the door through an arm, and the arm is a wearing part in a way the operator body is not.

Push arms are ordered by length and by finish, so a 20 inch push arm exists in aluminium and in bronze as two separate part numbers. If the arm has been bent by somebody forcing the door, the replacement has to match both.

Track driven operators use a different arrangement again, with the arm running in a track rather than folding at an elbow. Sliding door operators like the SlidePro series replace the arm entirely with a belt and carrier system. Those are three different parts families, so identifying which one you are looking at is the first step in any repair.

Can an Automatic Door Opener Go on a Fire Rated Door?

Yes, with conditions, and the conditions are the same ones that apply to any powered hold open arrangement.

A fire rated opening has to close and latch when the alarm sounds. An operator that holds a door open, or that simply sits in the way of the door closing under its own spring, has to release and let the door do its job. That means the operator and its hold open function need to be tied into the fire alarm, not left as a mechanical catch somebody can set and forget.

The rating on the door also constrains what can be cut into it or bolted to it. Our commercial door fire rating guide explains what each rating requires of the opening.

Which Operator Series Is on Your Door?

Identifying the series matters more than identifying the brand, because the parts lists are organised by series.

Swing door operators run across several families, including units built around an electrohydraulic mechanism, pneumatic units, and the Benchmark and Senior Swing families. Sliding operators sit in their own series. Each has its own motor, control box, arm set and accessory range, and very little crosses between them.

Start by reading the label inside the header cover. If that is gone, photograph the header end plates, the arm, and the control board, and work from the diagrams. Our commercial door operators guide covers the main models and what distinguishes them, and the Benchmark and Senior Swing parts guide covers those two families specifically.

What Goes Wrong With Automatic Door Openers?

For faults on the mechanical side of the same opening, our commercial door hardware troubleshooting guide covers closers, latches and strikes.

What Should You Confirm Before Ordering Operator Parts?

1. The operator series, read from the label inside the header.
2. The configuration, single, double or dual egress.
3. Swing or slide, because the parts families do not overlap.
4. The activation device, including gang size, icon and whether it is wired or wireless.
5. Arm length and finish, for anything that connects the operator to the door.
6. Whether the opening is fire rated, which constrains hold open.

Everything here is stocked at component level. Browse door operator parts, the wider LCN parts range, or the full products and parts index if you already have a part number.

About the Author

Security Parts has supplied repair parts for commercial door hardware since 2001, covering Von Duprin, LCN, Schlage, Falcon, Detex and Adams Rite at the component level. Our diagram based lookup exists so a technician can confirm a part before ordering it. This guide was written by the Security Parts team from supplier documentation and the questions our customers bring us.

For the rest of the powered opening, see our door closer parts section and our guide to the four main types of commercial door closer.

Quick Summary

Almost every commercial door closer you will touch is hydraulic. The word gets used so routinely that it stops meaning anything, which is a shame, because understanding what the oil is actually doing explains most of the faults people spend hours chasing.

This guide is about the mechanism rather than the model range. For the different types of closer and the grading system, see our guide to the four main types of commercial door closer.

How Does a Hydraulic Door Closer Actually Work?

There are two energy events in every cycle and it helps to keep them separate.

Opening. When somebody pushes the door, they are compressing a spring inside the closer body. All the energy that will later close the door is put in at this moment, by the person opening it.

The closer is not powered. It has no motor and nothing stored between uses.

Closing. When the door is released, the spring pushes back. If it were allowed to act freely the door would fly shut and slam.

So the spring has to drive a piston through a chamber of oil, and the oil can only escape through small passages. Those passages have needle valves in them, and how far each valve is open decides how quickly the oil gets out of the way.

That is the whole idea. The spring provides the force. The oil provides the timing. Almost every closer complaint resolves to one or the other, and telling them apart saves a great deal of fiddling.

What Do the Valves on a Hydraulic Door Closer Control?

The adjustment screws on the end of the body are not volume controls or strength controls. Each one meters the oil through a different part of the swing.

Backcheck is the one people misunderstand. It is not a door stop and it is not a substitute for one. It cushions the final part of the opening swing so the door is not flung into the wall, but a door that is regularly forced past its intended limit still needs a physical stop.

For the adjustment sequence itself, see our guide to adjusting a fire door closer, which covers the same valves with the compliance constraints that apply on a rated opening.

Why Spring Size Is a Separate Decision From the Valves

Closer size refers to spring strength, and it is matched to the door, not to how the door feels on the day. A wider or heavier door needs more stored energy to close it, so it needs a stronger spring.

Many modern closer bodies are adjustable across a range rather than fixed. A cylinder assembly described as adjustable size 1 through 4 covers several door widths in one part, which is why distributors can stock one unit for a large share of openings instead of six.

What that adjustability does not do is fix a timing problem. Winding spring strength up to force a sticky door shut masks a binding leaf and makes the door harder for everybody to open. Our commercial door closer sizing guide works through sizes against door width.

Why Does a Hydraulic Door Closer Behave Differently in Winter?

Because oil gets thicker as it gets colder. A fluid that flows easily through a needle valve at room temperature moves more reluctantly near freezing, and the door takes longer to close.

This produces a seasonal pattern that confuses people. An exterior door that behaved perfectly through summer starts failing to latch when the weather turns, and nothing on the door has changed. The valve settings are the same. The oil is simply slower.

Two practical consequences. First, set valves on an exterior closer with the season in mind, and expect to revisit the setting. Second, a door that only fails to latch on cold mornings is telling you it has very little margin, which usually means the spring is under sized for the opening or the door is dragging.

What Happens When a Hydraulic Door Closer Leaks?

It is finished. This is the single most useful thing to know about hydraulic closers.

The oil is not a lubricant that can be topped up. It is the working fluid, and the volume of it is what makes the control possible. Once a seal has failed, the closer is losing the thing that controls the door. Adjusting the valves at that point just redistributes a shrinking amount of fluid, and the setting will not hold.

Signs to look for:

• A film of oil on the door face below the closer, or drips on the floor.
• Oil weeping around the valve stems rather than from the body seam.
• A valve setting that has to be reset every few weeks.
• A door that was controlled and is now progressively getting faster.

Weeping from the valve stems alone is sometimes just over tightened or damaged valve seats. Oil from the body seam is a dead closer. Either way, the fix is a part, not an adjustment.

Hydraulic, Pneumatic and Powered: What Is the Difference?

Oil gives finer control than air, which is why it dominates commercial work. It also means the closer carries a fluid that can leak, which air cannot, and that is the trade. Powered openings still rely on controlled closing, so hydraulics often remain part of the picture even when the door opens itself. Our commercial door operators guide covers the powered side.

What Is a Hold Open Hydraulic Closer?

A hold open closer does everything described above and adds one function: at a chosen point in the swing, the door stays where it is put instead of closing.

Mechanically that is usually a detent in the arm or the track that catches the door at a set angle. The user swings the door past that point and it parks. Pull it back past the detent and the closer takes over again as normal.

Two things to know before specifying one. First, hold open is a property of the arm rather than the body on most surface mounted units, so the same closer can be ordered with or without it.

Second, mechanical hold open is not permitted on a fire rated opening. A rated door has to close on alarm, and a detent somebody has set does not release. Where hold open is genuinely needed there, it has to be an electrically released arrangement tied into the fire alarm.

Hold Open and the Latch Problem

A door parked at hold open for most of the day spends very little time actually closing, which hides a weakening closer. Nobody notices the door is losing power until the hold open is released during a drill and the door drifts shut without latching. Test rated doors from fully open with the hold open disengaged, not from the parked position.

How Long Should a Hydraulic Door Closer Last?

There is no single figure, because the answer depends on cycles rather than years. A closer on a store room used twice a day and one on a main corridor used two thousand times a day are not comparable, even if they are the same model fitted on the same date.

What is predictable is the order in which things go wrong.

The useful thing about that sequence is the middle stage. A closer that needs resetting every few weeks is giving you several months of warning before it starts dripping on a corridor floor. That is the moment to order the part, not after the leak.

How Do You Identify the Hydraulic Closer on Your Door?

Take the cover off. The body almost always carries a stamped or cast model number, and that number is the fastest route to the right part.

If the stamping is gone, the arm and mounting position narrow it to a family, and the valve layout on the end of the body is the next clue. Three valves in a row is a different unit from two valves plus a separate backcheck on the side.

Our surface mounted door closer guide covers the identification sequence in detail, and the door closer component guide explains what each part does.

What Maintenance Does a Hydraulic Door Closer Need?

Very little, and that is part of the problem. Closers are ignored until they fail.

1. Look for oil on the door face and the floor beneath, twice a year.
2. Check the door still latches from a fully open position without being helped.
3. Check the fixings are tight, particularly on hollow doors where screws work loose.
4. Check the arm is straight and that its connections are not worn oval.
5. Check there is a working door stop, because backcheck is not one.
6. Retest exterior doors seasonally, because the oil behaves differently in cold weather.

For faults on the rest of the opening, our commercial door hardware troubleshooting guide covers latches, strikes and exit devices. Browse door closer parts for cylinder assemblies, arms and covers, or start from the full products and parts index.

About the Author

Security Parts has supplied repair parts for commercial door hardware since 2001, covering Von Duprin, LCN, Schlage, Falcon, Detex and Adams Rite at the component level. Our diagram based lookup exists so a technician can confirm a part before ordering it. This guide was written by the Security Parts team from supplier documentation and the questions our customers bring us.

For more on the closer, see the LCN door closer parts and service guide and the full LCN parts range.

Quick Summary

Most commercial closers you will ever touch are surface mounted, and most people never think about the term until they need a part. Then it matters, because the first thing a supplier needs to know is whether the unit is sitting on the door or buried in it.

This guide is about the surface mounted family specifically: what defines it, how to work out which one is on your door, and the parts that only exist because the closer is mounted on the outside. For the full taxonomy of closer types, see our guide to the four main types of commercial door closer.

What Makes a Door Closer Surface Mounted?

A surface mounted closer has its body fixed to the outside of the opening. You can see it, touch it, and unscrew it without taking the door off its hinges or opening up the frame.

That is the whole definition. It says nothing about the size, the arm, the brand or the application. It says where the hydraulic body lives.

The alternative is a concealed closer, where the body is hidden inside the door leaf, inside the frame head, or in the floor beneath the door. Those require the opening to be machined for them, usually at the factory, which is why they are mostly specified for new work and almost never retrofitted into an existing door.

The Three Parts You Can See

On any surface mounted closer there are three visible elements, and naming them correctly makes every conversation with a supplier faster:

• The body, or cylinder assembly. The metal casting that holds the spring and the hydraulic fluid. This is the part that does the work and the part that fails expensively.
• The arm. The linkage from the body to whichever surface the body is not mounted on. Its shape is the quickest visual clue to how the closer is mounted.
• The cover. A shell that clips or screws over the body. Cosmetic, protective, and the thing most likely to be missing on a door that has been serviced badly.

The body carries a size. An adjustable cylinder assembly will state its range, for example a size 1 through 4 adjustable unit, which means one part covers several door widths rather than being fixed to a single spring strength.

Where Does the Body Sit on a Surface Mounted Closer?

Surface mounted closers go on in one of three positions, and the position decides what you are looking at when you stand in front of the door.

Top jamb is the one people forget is still surface mounted. The body has moved off the door and onto the frame, but it is still bolted to the outside of the opening, still visible, and still serviceable from a ladder. Hidden inside the frame head is a different thing entirely and is not surface mounted.

The arm itself is a deeper subject than this page needs to cover. Our door closer selection guide works through regular, parallel and top jamb arms in detail, including which to pick for which opening.

How Do You Identify the Surface Mounted Closer Already on Your Door?

This is the question that actually blocks most repairs. The closer is leaking or slamming, somebody needs a part, and nobody knows what the unit is.

Work through it in this order.

Take the Cover Off First

The cover is usually held by one or two screws at the ends, sometimes by a clip. Under it, the body almost always carries a stamped or cast model number, and often a date. That number is the answer, and everything else below is for when the number has worn away.

Read the Arm Shape

If the number is gone, the arm narrows it down fast. A straight two piece arm running from the door up to the frame head is a regular arm installation. An arm that runs from the body out to a bracket on the underside of the frame head is a parallel arm. A single rigid arm running into a track rather than folding at an elbow means a track arm closer, which is a different parts family again.

What to Photograph Before You Order

Six photographs will let any supplier identify a closer without guesswork:

1. The body with the cover removed, square on, so any stamping is readable.
2. The full opening from the side the closer is on, far enough back to show which face it is mounted to.
3. The arm, including where it lands on the frame or the door.
4. Any bracket or plate between the closer and the surface it is bolted to.
5. The adjustment valves on the end of the body.
6. Any label on the door edge, for fire rated openings.

If the unit is coming off anyway, our walkthrough of how to install a door closer on a commercial door covers what the replacement will need in terms of fixings and prep.

What Is a Drop Plate and Why Would a Surface Mounted Closer Need One?

A drop plate is a flat metal plate that goes between the closer and the surface it is mounting to. It exists for one reason: the surface is not giving the closer what it needs.

That sounds trivial. It is the single most common reason a closer that was ordered correctly cannot actually be fitted on the day.

The useful thing to understand is that two drop plates for the same mounting position can be solving two completely different problems. Two top jamb plates from the same family make the point:

One is about the ceiling above the frame. The other is about the frame being too narrow. Ordering the wrong one gets you a plate that bolts to nothing useful.

Measure the frame face before you order, and look up at what is above the frame. Those two observations decide the plate.

Why Do Surface Mounted Closers Have Covers, and Does It Matter Which One?

A concealed closer does not need a cover because nobody can see it. A surface mounted closer sits in plain view on a corridor door, so the cover does three jobs: it hides the body, it carries the finish that matches the rest of the hardware, and it keeps fingers and trolleys off the adjustment valves.

Two things about covers catch people out.

Covers come in the full finish range. The same metal cover will be listed in a long list of powder coat and plated finishes, from aluminium and dark bronze through to satin chrome and satin nickel. Ordering the right part number in the wrong finish gives you a working closer that looks wrong on the door. Our commercial door hardware finish guide explains how the finish codes map to each other.

A cover can be handed even when the body is not. This is the one that produces returns. A standard cylinder assembly is frequently non-handed, so one part serves both left and right hand doors.

The metal cover for that same closer can still be offered as a left hand or a right hand part. Non-handed body does not mean non-handed cover, and the handing has to be stated when you order.

Surface Mounted or Concealed: Which Belongs on Which Door?

This is a design decision on new work and almost never a real choice on an existing opening, because the door either has the pocket machined into it or it does not.

Neither is better. They are answers to different questions. A facilities team maintaining a building full of existing doors will deal almost entirely with surface mounted units, because that is what is already fitted and what can be replaced without a carpenter.

Is a Surface Mounted Door Closer Handed?

The body usually is not. Many surface mounted closer bodies are explicitly non-handed, which is part of why they are stocked so widely: one unit covers both hands of door.

What is handed, or can be, is everything around the body. Covers are the obvious one. Some arms and hold open arms are non-handed and some are not, and the description on the part is the only thing that settles it. An arm described as non-handed, supplied with a long head and tube for top jamb mounting, is telling you both that it fits either hand and that it is intended for one specific mounting position.

So the practical rule is simple. Do not assume the whole assembly inherits the handing of the body. Check the handing on each part you are ordering.

What Changes on a Fire Rated Door?

A surface mounted closer on a fire rated opening is doing a life safety job, not a convenience job. It has to close and latch the door every time, not merely swing it most of the way shut.

Three things follow from that. The closer has to be a listed unit suited to the rating of the opening. Hold open, where it is used at all, has to release on alarm rather than being a mechanical catch that somebody leaves set. And the spring strength cannot simply be wound down to make the door easier to open, because the door still has to overcome the latch.

That last point is where well intentioned maintenance goes wrong most often. Our guide to adjusting a fire door closer covers the compliance side, and the commercial door fire rating guide explains what the rating on the opening actually requires.

Why Do Surface Mounted Closers Dominate Retrofit Work?

Four reasons, and they all come back to the body being on the outside.

• No machining. Fitting one means drilling and bolting, not routing a pocket into a door leaf that may be fire rated and cannot legally be cut on site.
• The door stays hung. A concealed unit in the door often means taking the leaf off. A surface unit is replaced with the door in place.
• Adjustment without disassembly. Sweep, latch and backcheck valves are on the end of the body, reachable with the cover off and the door hanging normally.
• Parts are available at component level. Arms, covers, plates, screws and cylinder assemblies are all separately replaceable, so a damaged arm does not mean a new closer.

That last point is worth taking seriously on a maintenance budget. A great many closers get replaced whole when a single part had failed. Our door closer component guide walks through what each part does and which ones are worth replacing on their own.

What Fails on a Surface Mounted Door Closer?

Being exposed is the advantage and the weakness. A surface mounted closer takes knocks that a concealed one never sees.

Why Winding the Valves Further Is Rarely the Answer

When a closer stops behaving, the instinct is to reach for the valves. Sometimes that is correct. But the valves control how the spring energy is released, not how much of it there is. If the body has lost fluid or the spring has weakened, more valve adjustment just moves the problem around and can empty the body faster.

The test is whether the adjustment holds. A valve that needs resetting every few weeks is telling you the body is finished. For faults elsewhere on the opening, our commercial door hardware troubleshooting guide covers latches, strikes and exit devices on the same door.

What Should You Confirm Before Ordering Parts?

Seven details, and the first one settles most of the rest.

1. The model number from the body, read with the cover off.
2. The mounting position, regular arm, parallel arm or top jamb.
3. Whether the arm is a folding arm or runs in a track, because the parts families differ.
4. The handing of the door, for any part whose description mentions hand.
5. The finish, matched to the rest of the hardware on the opening.
6. Whether a plate or bracket is already fitted, and if so what it is doing.
7. Whether the opening is fire rated, which constrains what you are allowed to fit.

With the model number and the mounting in hand, everything else follows from the diagram. Start from the door closer parts section, or the full products and parts index if you already have the part number.

About the Author

Security Parts has supplied repair parts for commercial door hardware since 2001, covering Von Duprin, LCN, Schlage, Falcon, Detex and Adams Rite at the component level. Our diagram based lookup exists so a technician can confirm a part before ordering it. This guide was written by the Security Parts team from supplier documentation and the questions our customers bring us.

For the rest of the closer, see our commercial door closer sizing guide, the LCN door closer parts and service guide, and the full LCN parts range.

Quick Summary

Two switches turn an ordinary opening into a monitored one, and they are constantly mixed up. A technician is told the door needs monitoring, fits one switch, and the panel still throws a forced door alarm every time somebody leaves. The hardware is fine. The wrong switch was fitted, or the right switch was wired to the wrong contact.

This guide covers both devices at component level: what each one senses, how the contacts behave, which part fits which door, and what the wiring actually has to do at the panel. For how these switches sit inside a wider electrified opening, see our access control and door hardware integration guide.

What Is a Door Position Switch and What Does It Actually Monitor?

A door position switch, usually shortened to DPS, monitors whether the door is open or closed, independent of the latch state. That last part is the bit people miss. The switch watches the gap between the leaf and the frame. It does not know whether the latch bolt has thrown, whether the lock is secure, or who opened the door.

Physically it is two pieces. A switch body goes in the frame and a magnet or actuator goes in the door edge opposite it, so closing the door brings them together and changes the state of the contacts. Pull the door open and the contacts change back.

That single piece of information drives most of what an access control system does after the door opens:

• Door forced open. The door went open with no valid credential and no exit request. Without a DPS the panel cannot detect this at all.
• Door held open. The door has been open longer than the allowed time, so something is propping it.
• Relock on close. Fail secure hardware can be told to drop back to locked the moment the door closes, rather than waiting out a fixed timer.
• Interlocks and operators. Automatic operators and mantraps need to know the leaf is closed before the next thing is allowed to happen.

Why the Latch State Is a Separate Question

A closed door is not a locked door. A door can sit closed against the stop with the latch bolt held back, and a DPS will happily report closed. If you need to know that the opening is actually secured, you need latch monitoring as well, which on an exit device is a different switch entirely.

What Is a Request to Exit Switch and Why Is It Required?

A request to exit switch, written RX or REX, generates a signal to the access control panel whenever the push bar or touch pad is actuated. It is how the panel tells a person leaving the building from a person forcing the door.

Without it the system has no way to interpret an opening from the inside. Somebody pushes the bar, the door swings, the DPS reports open, and because no credential was presented the panel calls it a forced door. Every legitimate exit becomes an alarm, and within a week nobody is reading the alarms any more.

On access controlled egress doors the request to exit signal is not optional. The egress side has to stay mechanically free, so the building relies on the RX signal to keep the monitoring honest rather than restricting the exit itself.

How the Shunt Window Works

When the RX contact changes state, the panel records an egress event and suppresses the door forced alarm for a set period, typically in the range of five to ten seconds. That window is called the shunt. The door is expected to open and close again inside it.

Two things go wrong with shunt timing. Set it too short and a slow closer or a person holding the door produces nuisance alarms. Set it too long and somebody can push the bar, prop the door and walk away with the alarm suppressed. The shunt is a security setting, not just a convenience setting.

Door Position Switch vs Request to Exit: What Is the Difference?

Put plainly: the DPS watches the door, the RX watches the hardware being operated. A monitored opening normally needs both, wired to two separate panel inputs.

What Do the Exit Device Switch Codes RX, LX, SS and LC Mean?

On exit devices the monitoring is not a separate box on the wall. It is a switch kit inside the device, ordered as a suffix on the part number. Four codes come up constantly and they are not interchangeable.

Why LX and RX Are Not the Same Thing

This is the ordering mistake that costs the most. LX reports the latch bolt. RX reports the egress event. A door can give you a clean LX signal and still produce forced door alarms all day, because the panel was never told that somebody pushed the bar.

SS sits between them. It is simpler than RX because it monitors the bar being depressed rather than the latch retracting, which is enough for a basic egress signal but tells you nothing about whether the device actually released.

Kits are also length specific. A switch kit built for a 48 inch device will not serve a 36 inch device, so the device width has to be confirmed before the kit is ordered. Browse the exit device parts section for the switch kits that match your device.

Which Door Position Switch Fits Which Door?

Door position switches are not generic. The two things that decide the part number are how it mounts and what the door and frame are made of. A switch bored into a hollow metal frame is a different part from the one that surface mounts on an aluminium storefront.

Concealed switches disappear into the opening and cannot be tampered with from the occupied side, but they need a prep in both the door edge and the frame. That prep is straightforward on a new opening and a real job on an existing one. Surface mount magnetic switches need no prep at all, which is why they dominate retrofits, but they are visible and they sit where a trolley or a cart can hit them.

What Do SPDT, Form A, Form B and Form C Mean?

Nearly every spec sheet for these switches uses contact form language, and getting it wrong is how a monitored door ends up quietly unmonitored.

Most of the door position switches on this site are SPDT, which is the same thing as Form C. The Schlage 679-05 provides normally open and normally closed contacts from the one device, and the Schlage 7766 is also SPDT. That gives you a choice at install time, and the choice matters more than it looks.

Normally Closed Is Usually the Safer Default

Wire a DPS on the normally closed contact and the circuit sits closed while the door is shut. Open the door and the circuit breaks, so the panel sees a change. Cut the wire, pull the switch off the frame, or lose a connection in the loop and the panel also sees a break. The failure looks like an alarm.

Wire the same switch normally open and a cut wire looks exactly like a door that is sitting quietly closed. Nothing is reported. On a door that matters, supervise the loop or use the normally closed contact so that a fault announces itself.

How Do You Wire a Door Position Switch?

The electrical side is simple. The complications are mechanical and they are all about the gap.

The switch is a dry contact into a monitor input on the panel or controller. Two conductors run from the switch to that input, and the panel supplies whatever small voltage it needs to sense the state.

The ratings are modest for the same reason. The Schlage 679-05 and 679-05HM are rated 0.3 amps at 30 VDC, and the 7766 is rated 0.25 amps at 30 VDC. These are signalling contacts, not switching contacts. Never run lock current through them.

What actually causes trouble on site:

• Alignment. Magnetic switches have a working gap. Push past it and the contacts stop changing reliably, so a door that looks shut reports open. A sagging door, a worn hinge or a closer that is not pulling the leaf fully home all show up here first.
• Which leaf it goes on. On a pair, the switch belongs on the active leaf unless both leaves need monitoring, in which case you need two switches and the panel has to treat them sensibly.
• Getting the wires across. If the switch sits in the door rather than the frame, the conductors have to cross the hinge line, which means a power transfer or an electrified hinge. Our electric power transfer guide covers how to do that without creasing a conductor.
• Keeping signal away from power. Run the monitoring pair separately from lock power. Shared conduit with a switching load is a reliable way to manufacture phantom door events.

How Do You Wire a Request to Exit Switch?

An RX switch is also a dry contact, but it can be used in two completely different ways, and conflating them is the root of most REX confusion.

Shunting Versus Unlocking

Shunting is the normal case. The RX contact goes to the panel's request to exit input. Somebody pushes the bar, the panel opens the shunt window, the DPS reports the door opening, and no alarm is raised. The lock itself does nothing, because an exit device already releases mechanically.

Unlocking applies where the egress side is not mechanically free, for example a fail secure electric strike on a door with a lever that is locked from the inside. Here the request to exit device, often a sensor or a button rather than a bar switch, has to actually release the lock. That is a different circuit with life safety consequences, and it is the case where a failed switch traps people rather than just producing a nuisance alarm.

Know which of the two you are building before you pick the part. For the broader comparison of what releases a door and when, see our guide to an electrified mortise lock versus an electric strike and our electromagnetic lock parts guide, since a maglock opening handles egress differently again.

Switch Kits Are Device Specific

A request to exit switch for an exit device is ordered against the device family and the device width. A Von Duprin 050251-CON request to exit switch with connector installed, for example, is listed as fitting 22, 33A, 35A, 98 and 99 style devices. Confirm both the series and the rail length before ordering, and check the Von Duprin 98/99 series parts manual if you are working on those devices.

What Do Electronic Locks Use Instead of a Separate Switch?

Standalone and networked electronic locks often carry their own monitoring rather than relying on a switch in the frame. The request to exit function is built into the lever, because turning the inside lever is itself the egress event, and the lock reports it over its own connection.

Door position is the part that still needs hardware. On Schlage NDE series locks the door position function is supplied as a DPS wiring kit containing a magnet, a switch and a wiring harness. The same part is listed for LE series mortise deadbolt locks as an external DPS kit. If the lock was ordered without it, the function is simply absent until the kit is fitted.

Mortise locks can also carry signalling internally. A signal switch mortise lock reports hardware operation from inside the lock case, which keeps the monitoring hidden and removes a separate device from the frame. For the mechanical side of those lock bodies, see our Schlage L series mortise lock component guide.

How Does Door Position Monitoring Work on an Automatic Operator?

On an automatic door operator the switch is doing something different again. It is not feeding an alarm panel, it is feeding the operator's own safety logic.

The LCN 8310-805 is a surface mount door position switch that disables the approach side sensor when the door is closed. It is applied with the 8310-804-1 or 8310-804-2 door mounted safety sensor and the 8310-845 relay module, working with an electrohydraulic, pneumatic or Benchmark automatic operator. A concealed version, the 8310-805C, covers installations where a surface device is unacceptable.

The reason this exists is that a door mounted sensor sweeps a different area as the leaf swings. Leaving the approach side sensor active through the whole cycle produces false detections and a door that will not settle. The position switch tells the operator which part of the cycle it is in.

Should You Use a Magnetic or a Mechanical Door Position Switch?

Both are in service everywhere and the choice is usually decided by the opening rather than by preference.

Magnetic switches use a reed contact in the switch body and a magnet in the door. Nothing touches, so there is nothing to wear out and nothing to bind when the door is slightly out of alignment, within the working gap. They are the practical choice for high cycle doors and for retrofits, since the surface mount versions need no door prep.

Mechanical plunger switches use a physical actuator that the door depresses as it closes. They are not fooled by an external magnet, which matters where tampering is a real concern, but the plunger is a moving part in the path of the door and it wears.

Where tamper resistance is the whole point, high security balanced magnetic switches exist as a separate class, built so that holding an external magnet against the frame does not defeat them.

What Goes Wrong With These Switches and How Do You Find It?

Almost every fault on a monitored opening reduces to one of six things. Work down this list before replacing anything.

For faults that are mechanical rather than electrical, our commercial door hardware troubleshooting guide covers the closer, latch and strike side of the same opening.

What Should You Confirm Before Ordering?

Six details decide whether the part that arrives is the part that fits.

1. Which function you actually need. Door position, request to exit, latch monitoring, or more than one of them.
2. Mounting. Concealed, which needs a prep, or surface mount, which does not.
3. Door and frame material. Hollow metal, wood and aluminium take different parts.
4. Contact form and rating. Confirm the switch gives you the contact you intend to wire, and that the panel input sits inside the switch rating.
5. Device series and length, for anything that goes inside an exit device.
6. Whether the conductors cross the hinge line, which decides if you also need a power transfer.

Everything in this guide is stocked at component level. Start from the full products and parts index if you already know the part number, or work from the diagram for your device.

About the Author

Security Parts has supplied repair parts for commercial door hardware since 2001, covering Von Duprin, LCN, Schlage, Falcon, Detex and Adams Rite at the component level. Our diagram based lookup exists so a technician can confirm a part before ordering it. This guide was written by the Security Parts team from supplier documentation and the questions our customers bring us.

For the rest of the electrified opening, see our electric strike schematic diagram, the Von Duprin QEL conversion kit guide, and our explanation of what delayed egress is and when code requires it.

Mortise cylinder vs rim cylinder is one of those distinctions that looks obvious once you are holding both parts and is almost impossible to resolve from a photograph on a phone. This guide covers how each one mounts, the measuring convention that causes most wrong orders, why the cam matters more than the length, and the short list of checks that stops a cylinder going back in the box.

Quick Summary

A mortise cylinder has a threaded brass body that screws into the lock and drives the lock with a rotating cam on the back. A rim cylinder has a flat back with a long flat tailpiece and mounts with two screws from the inside face of the door. The lock body decides which one you need, not the door and not the key.

Key points

• Start at the lock, not the cylinder. Mortise lock bodies take mortise cylinders. Rim exit devices take rim cylinders.
• The cam is the variable that fails you. A wrong cam threads in perfectly and still will not operate the lock.
• Nominal length is a designation, not a caliper reading. Manufacturers do not all measure from the same datum.
• Jumbo and standard are different diameters. That is why a cylinder sometimes will not start on the thread at all.
• Rim tailpieces get cut to length in the field. Longer is not safer, and excess can bind the lock.
• Collars make up the difference when the cylinder would otherwise sit proud of the trim.

What Is the Difference Between a Mortise Cylinder and a Rim Cylinder?

The difference is how the cylinder attaches and how it transmits motion into the lock. Everything else follows from those two things.

A mortise cylinder threads into a tapped hole in the lock or the door. A set screw in the edge of the lock drops into a groove machined around the cylinder body and holds it from backing out. Because that groove has to line up with the screw, the cylinder has to finish at the correct rotational position, which the trade calls clocking it.

A rim cylinder does not thread into anything. It sits against the outside face of the door, and two long screws pass through the door into the back of the cylinder, usually through a mounting plate on the inside. A flat tailpiece projects back through the door and engages the device.

Both types share the same body diameter in commercial sizes, which is why they look so similar in a parts drawer and so different the moment you turn them over.

How Do You Tell Which One You Are Holding?

Look at the back, not the face. The face of the two is nearly identical.

1. Is there a thread on the body? Thread means mortise. A smooth body means rim.
2. What sticks out of the back? A cam is a flat plate that rotates around the cylinder axis. A tailpiece is a long flat bar that projects straight back, a bit like a screwdriver blade.
3. Is there a groove around the body? Mortise cylinders carry a groove for the set screw. Rim cylinders do not.
4. Are there two screw holes in the back? That is a rim cylinder, and those screws come from the inside of the door.

The quickest field shorthand is motion. A mortise cam rotates and catches a plate that pulls back into the lock body. A rim tailpiece rotates and drives the device directly.

Which Lock Takes Which Cylinder?

Work from the device on the door. This is the step that prevents most wrong orders, because people tend to start from the cylinder they removed rather than from what it was fitted to.

If the device is a rim exit device, our guide to rim exit devices covers the trim functions that decide whether you need a cylinder at all. For mortise bodies, Schlage L series mortise lock component guide walks through the component categories.

Where Do You Measure a Mortise Cylinder From?

This is the question that generates the most returns, and the honest answer is uncomfortable: the convention is not uniform across manufacturers.

Published guidance variously describes measuring from the underside of the cylinder head to the back of the cylinder including the cam, from the front of the face to the back of the brass body excluding the tailpiece, and from under the head to the outside of the cam. These are not all the same datum, and they do not all give the same number on the same part.

On top of that, at least one major manufacturer states the brass body length only while others include the cam. The practical consequence is that a cylinder sold as a given nominal size may not measure that figure with calipers.

What Are the Standard Mortise Cylinder Lengths?

Commercial stock sizes cluster tightly. The three you will meet most often are 1 inch, 1-1/8 inch and 1-1/4 inch, and 1-1/8 inch is the general purpose default on a standard door.

What If You Do Not Have the Old Cylinder?

Without the original part you are working backwards from the opening. The inputs are the door thickness, how far the trim or escutcheon stands off the door face, and how thick the collars are on each side. One approach used in the trade adds the collar thicknesses to the door thickness, subtracts the trim standoff, and halves the result to get a per side length.

Treat that as a starting point rather than a published standard, because it assumes a symmetrical opening and it depends on knowing the lock. A cylinder that lands slightly short simply will not reach. A cylinder that lands long gets corrected with collars, which is the next section.

Why Will a Cylinder Sometimes Not Thread In at All?

Because it is the wrong diameter, not the wrong length. The standard commercial mortise body is roughly 1-5/32 inches across, and jumbo cylinders run about 1-1/2 inches. A jumbo will not start in a standard prep and a standard will spin loosely in a jumbo one.

People reliably diagnose this as a cross threaded cylinder and keep forcing it. Check the diameter before you blame the thread. For reference, the thread specification on some major commercial lines is published as a 1.150 inch diameter at 32 threads per inch.

What Are Collars and Spacer Rings For?

A collar is a ring that sits between the cylinder head and the door or trim. It does two jobs. It takes up the gap so the cylinder finishes flush instead of standing proud, and on the outside of an opening a hardened collar also resists wrenching attacks.

Collars are the standard correction when the nearest stock cylinder length is slightly too long for the opening. They are also the part most often forgotten on the order, which is how a technically correct cylinder still ends up looking wrong on the door.

• Trim or decorative ring. Cosmetic, closes the gap around the cylinder face.
• Spacer collar. Structural, adjusts how far the cylinder sits into the lock.
• Security collar. Hardened, fitted to the outside to resist attack on the cylinder.
• Blocking ring. Supplied by some makers as a specified part, with dimensions called out at order.

Common collar thicknesses in the trade pair with the common cylinder lengths, so a shorter cylinder generally takes a thicker collar to finish flush. Confirm against the lock you are working on rather than ordering by habit.

What Is a Cam, and Why Will the Wrong One Stop the Lock Working?

The cam is the flat plate on the back of a mortise cylinder. When the key turns, the cam rotates and engages a part inside the lock that retracts the bolt or latch. If the cam does not sit where the lock expects it, the key still turns and nothing happens.

That failure mode is the single most misleading one in this whole subject. The cylinder threads in cleanly, the key rotates smoothly, and everything feels correct. A buyer reasonably concludes the cylinder fits. It does not operate.

Can You Just Swap the Cam?

Usually yes. On most conventional cylinders the cam is held by screws and can be changed, which is why cylinders often ship with a second cam loose in the bag. Keep the screws, because seized or damaged cam screws are a far more common problem than a worn cam.

There are exceptions. At least one interchangeable core range has the cam assembled at the factory and not intended for field swapping, which means the cam has to be specified as a suffix on the purchase order. If you cannot find a way to remove a cam without force, stop and check whether that line is field serviceable before you damage the housing.

Space is the other constraint nobody mentions. Some lock bodies, particularly in narrow stile applications, simply do not have room for a larger cam profile regardless of what the catalogue lists as compatible.

How Long Should a Rim Cylinder Tailpiece Be?

Long enough to engage the device and no longer. Tailpieces are supplied oversized and scored so they can be shortened in the field, and cutting one to suit the door is routine work rather than a modification.

The instinct to leave it long causes problems. Some rim locks need only a small amount of engagement, and excess tailpiece can bottom out and bind the mechanism. The scored segments are a guide to where to cut, not a statement that every segment should be used.

• Match the old part. Measure how far the original protruded past the inside face and reproduce it.
• Cut square. A clean cut goes back through the door prep far more easily than a burred one.
• Check the orientation. Some device trim accepts the tailpiece either vertically or horizontally, using a guide inside the chassis.
• Shorten the mounting screws too. Rim mounting screws are usually scored for the same reason, and they are a separate operation from the tailpiece.
• Do not over tighten the mounting screws. Pulling them down hard is a documented cause of a rim cylinder that turns stiffly.

A bent or twisted tailpiece is a symptom, not a cause. If one keeps deforming, something else is binding, the trim is not aligned to the device, or the trim is not rated for the device it is driving.

What Are SFIC, FSIC and KIK Cylinders?

An interchangeable core is a cylinder whose working core can be pulled out and replaced without taking the lock apart. A separate control key retracts a retaining lug and releases the core, which is what makes rekeying a large estate practical.

Two points cause confusion at the counter. The core and the housing are ordered separately, so a mortise interchangeable core cylinder is a housing plus a core, not one part. And the words cylinder, core, plug and housing get used interchangeably when they describe different things, which is worth being precise about on a purchase order.

If you are planning a key system rather than replacing one cylinder, our master key system design guide covers levels of keying and construction keying, and the Schlage key systems guide covers keyway families and cylinder formats.

What Goes Wrong When People Order Cylinders?

Almost every wrong order traces back to one of six things. None of them are exotic.

Before you place the order, write down six things: the lock make and model, the cam pattern, the nominal length, the finish code, the keyway, and whether the cylinder has to work on an existing key system. That list closes almost every gap. Our commercial door hardware finish guide covers the finish codes if you are matching an existing opening.

About the Author

Security Parts has supplied repair parts for commercial door hardware since 2001, covering Von Duprin, LCN, Schlage, Falcon and Detex at the component level. Our diagram based lookup exists so a technician can confirm which part they need before ordering rather than after. This guide was written by the Security Parts team from supplier documentation and the questions our customers bring us.

For related reading, see our thumbturn cylinder guide for the keyless side of the same opening, and cylindrical lock parts and diagrams for the format that takes neither a mortise nor a rim cylinder.

The moment a lock, an exit device or a switch sits on the moving leaf instead of the frame, you need a way to carry current across the hinge line. An electric power transfer is one of three methods, and picking the wrong one is how installers end up with intermittent faults that look like a defective lock. This guide covers all three, the wire counts and current limits that decide between them, and where the prep actually goes.

Quick Summary

An electric power transfer is a hinged, armored unit mortised into the frame and the door edge that carries low voltage conductors into a moving door. The two alternatives are a through wire hinge, which needs almost no extra prep, and a surface mounted door loop, which is the cheapest and the most exposed. The choice comes down to how many conductors you need, how much current the device on the door draws, and whether the opening is labeled.

Key points

• The number in EPT-10 is the wire count, not the gauge. Ten 24 AWG conductors carry less current than the EPT-2's two 18 AWG conductors.
• Electric latch retraction is the deciding factor. A motorized device is easy to feed. A solenoid device with a large inrush is not.
• The published mounting position is about 6 inches below the top hinge. Frame prep and door prep have to align.
• Hinge width caps the door swing. Wider butt hinges reduce how far the door can open with an EPT fitted.
• You do not need a transfer for an electric strike. The strike lives in the frame, so nothing crosses the hinge line.
• On a labeled opening the cutouts normally have to be factory made, which is why retrofitting a transfer into a rated door is a problem.

What Is an Electric Power Transfer and When Do You Need One?

An electric power transfer is a two part armored unit. One half mortises into the frame, the other into the door edge, and a jointed arm between them carries the conductors through the swing. The joint is built so the wires flex at a controlled point instead of being bent and pinched wherever the door happens to move.

You need one whenever the electrified component sits on the leaf that moves. That is the whole test. If the powered part is in the frame, nothing has to cross the hinge line and no transfer is required.

The common Von Duprin units measure roughly 9 inches long by 1-1/4 inches by 1-5/8 inches, and the door needs to be at least 1-3/4 inches thick. The frame requires reinforcement of at least 0.060 inch to take the tapped mounting holes.

Which Devices Need Power Taken Into the Door?

This is the table that decides the specification, and it is the one most commonly skipped. Count the conductors for every function on the door, not just the lock, because the request to exit switch and the latch monitor usually get added after the frame is already set.

One transfer serves one powered leaf. A pair of doors with electrified hardware on both leaves needs two. If you are working out which exit device option you actually have, the Von Duprin 98/99 series parts manual lists the option codes by letter, and the QEL conversion kit guide covers what a motorized conversion involves.

EPT, Electrified Hinge or Door Loop: Which Should You Use?

All three move current across the same gap. They differ in how much prep they demand, how well they protect the conductors, and how easy they are to service when something fails years later.

The honest summary is that the door loop wins on price and loses on everything else, the hinge wins on appearance and loses on conductor capacity, and the power transfer costs the most and causes the fewest problems over the life of the opening.

What Does the 10 in EPT-10 Actually Mean?

It is the number of conductors. Not the gauge, and not the current rating. This trips up more buyers than any other detail on the topic, because the instinct is to read a bigger number as a bigger part.

The EPT-10 carries ten 24 AWG wires. The EPT-2 carries two 18 AWG wires. Thicker conductors carry more current, so the EPT-2 is the higher capacity unit despite the smaller number in the name.

Some specifiers deliberately order the ten wire unit even when two conductors would do, purely so there are spare conductors available when someone adds a monitoring function later. That is a reasonable call on a new opening, provided nothing on the door needs more current than thin conductors can carry.

Why Does Electric Latch Retraction Change the Wire Calculation?

Most electrified trim and monitoring draws very little. Latch retraction is different, because pulling the latches back takes a burst of current far above what the device needs to hold them there.

Motorized latch retraction is the easy case. A published Von Duprin figure for a motorized device is an inrush of 1.0 A for half a second, settling to 0.14 A to hold. That feeds comfortably from a standard power supply and a sensibly sized conductor.

Solenoid driven latch retraction is the hard case. Trade sources report inrush figures an order of magnitude higher, which is why these devices call for a dedicated supply or a booster module rather than being powered through an access control panel output. Panel relay contacts are frequently rated only a few amps, and panel outputs are often fused individually well below the unit's total rating.

Here is the practical conclusion. Ten 24 AWG conductors rated for 1 A are correct for trim, switches and monitoring, and categorically wrong as the only power path for a high inrush solenoid device. On that kind of opening the usual answers are a two wire transfer sized for the latch retraction power with a separate route for signal, or specifying a motorized device so the inrush problem disappears.

• Size the whole run, not just the transfer. The transfer is a short, thin section in a longer circuit, and it has to be factored into the total.
• Keep the run from the transfer as short as practical. Manufacturer guidance says so explicitly.
• Do not splice a small conductor to a large one to gain capacity. Current forced through the thinner wire is a fire risk.
• Power a high inrush device from its own supply and let the access panel trigger it rather than feed it.

Where Does an EPT Mount on the Door?

On the hinge side, approximately 6 inches below the top hinge. The published measurement runs from the bottom of the top hinge to the top of the power transfer. The same position is recommended on continuous hinge doors for consistency.

The prep in the frame and the prep in the door edge have to line up, which sounds obvious and is the most common reason a transfer binds. On metal frames the unit takes tapped mounting holes in twelve places and a one inch opening through to the wire channel.

Older buildings often have the transfer much lower, sometimes between the bottom hinges. That is a legacy of a period before these units were listed, when they had to sit below a certain height on rated frames. Facilities with cart and gurney traffic tend to dislike the low position for obvious reasons.

Which Hinges and Pivots Can an EPT Work With?

This is the table that stops a part being ordered and then found unusable. Wider hinges push the door further from the frame as it swings, which progressively limits how far it can open before the transfer runs out of travel.

Continuous hinges work, but the hinge leaves need prepping too. Geared continuous hinge ranges are commonly supplied with standard cut outs sized for the common transfer units, and the cut out location is measured from the top of the hinge to the centreline of the opening rather than to its top edge.

On a centre pivot door there is no usable transfer position at all. The pivot itself becomes the only practical route, which means an electrified pivot rather than an EPT.

Can You Use an Electric Power Transfer on a Fire Rated Door?

Yes, when the unit carries the right listing. Common Von Duprin transfers are listed against the standards that cover fire door accessories, and some systems also need the access control listing depending on what they feed.

The complication is the prep, not the product. On a labeled opening the cutouts normally have to be made by the door and frame manufacturer under their listing. Field cutting a transfer into a door or frame that already carries a label is how a compliant opening quietly becomes a non compliant one.

That is why trade sources sometimes state flatly that power transfers cannot be retrofitted into fire rated openings. The accurate version is narrower: the device is listed, but the prep has to happen under the right conditions. For fire rated hardware in general, our commercial door fire rating guide sets out what each rating permits.

Fire rated wood doors have one extra requirement worth noting. A back box is required, and the rear knockout is the one to use rather than the bottom.

What Goes Wrong With Power Transfers?

Transfer faults are distinctive because they are movement dependent. A lock that misbehaves only at certain door positions is almost never a faulty lock.

Two installation habits prevent most of this. Fit the strain relief that comes with the unit, and leave the elbows roughly half an inch of free movement when pulled straight out so the joint is not loaded at rest.

Which Templates and Documents Do You Need?

Three Von Duprin documents cover the common transfers, and knowing their numbers saves a long search. The template for metal frames and the template for wood doors are separate documents, and the installation instructions carry a dimensioned template on the back page.

1. Metal frame template, document 107293. Covers the frame and door edge prep for the standard units.
2. Wood door template, document 109342. Use this one for wood door applications rather than adapting the metal template.
3. Installation instructions, document 107717. Carries the swing limits, the rating table and the dimensioned template.

Before ordering, confirm four things: the conductor count against every powered function on the leaf, the current the heaviest device draws, the hinge or pivot type and the swing the door needs, and whether the opening is labeled. Get those four right and the part fits the first time.

About the Author

Security Parts has supplied repair parts for commercial door hardware since 2001, covering Von Duprin, LCN, Schlage, Falcon and Detex at the component level. Our diagram based lookup exists so a technician can confirm a part before ordering it. This guide was written by the Security Parts team from supplier documentation and the questions our customers bring us.

For the wider electrified opening, see our access control and door hardware integration guide, the comparison of an electrified mortise lock versus an electric strike, and the step by step on how to install an exit device.

An electromagnetic lock looks like the simplest device on a commercial opening. It is a coil, a steel plate and two wires. Most of the service calls it generates come from a handful of parts and settings that almost nobody writes down, so this guide names every component, explains how holding force is actually rated, sets out the egress rules the lock has to meet, and gives you a symptom to cause table for the day it stops holding.

Quick Summary

An electromagnetic lock is a coil in a steel housing that is mounted to the frame head, plus a steel armature plate bolted to the door. Energize the coil and the magnetic bond between the two holds the door shut. Cut the current and the bond disappears, which is why every direct pull maglock is fail safe by design.

Key points

• Holding force is not about door weight. The hinges carry the weight. The rating describes the pull needed to break the magnetic bond.
• The armature plate is meant to float slightly. Over tightening the sex bolt stops it seating flush and is the most common install fault.
• Two release methods are recognised by the model codes. Sensor release and door hardware release. Section numbers move between code editions, so confirm with your authority having jurisdiction.
• A maglock does not replace positive latching on a fire rated opening. The latch stays, and the lock itself has to be labeled for fire door use.
• Slow release is usually a diode, not magnetism. Fit the suppression the manufacturer calls for and check whether the lock already has it inside.
• Use 24 VDC on long runs. The same lock draws roughly half the current, so voltage drop hurts you far less.

What Is an Electromagnetic Lock and How Does It Work?

An electromagnetic lock is an electrically operated holding device with no latch, no bolt and no keyway. Current through a coil magnetizes a stack of ferrous plates inside the lock housing. A machined steel armature plate on the door is drawn against the machined face of the housing, and the bond between the two resists anyone pulling the door open.

The behaviour that matters is what happens when the current stops. The bond collapses immediately and the door is free. That single property is why maglocks are treated as a special locking arrangement in the egress sections of the model codes rather than as ordinary door hardware.

Two families exist. A direct pull maglock resists force pulling straight off the magnet face and suits a single swinging door. A shear lock sets locating pins or tabs into recesses in the magnet face, so the load acts across the joint instead of straight off it. That mechanical interlock is what lets shear locks work on double acting doors and on sliding doors, where a header mounted direct pull magnet will not hold.

What Are the Parts of an Electromagnetic Lock?

Most published descriptions stop at "a magnet and a plate". A service tech ordering a replacement needs the rest of the stack, because the mounting hardware fails far more often than the coil does.

Why the Armature Plate Has to Float

Manufacturer instructions describe the armature as designed to pivot slightly so it can compensate for reasonable misalignment. That pivot is the whole point of the rubber washer in the fastener stack. Torque the sex bolt down hard and the plate becomes rigid, which means it can no longer self align against the magnet face.

The field symptom is a lock that reports energized but can be pulled open by hand. Technicians commonly back the armature bolt off between half a turn and a full turn so the plate can snap flat. Treat that as trade practice consistent with the published design intent rather than as a torque figure from a manual.

What the Mounting Hardware Does, and Why It Falls Off

Maglocks are heavy, and they are held on by a small number of fasteners into a frame head. Thread locking compound ships with most units for exactly that reason, and skipping it is a known cause of units working loose over weeks rather than failing outright.

• Use the supplied fasteners. Self tapping screws into a frame head are not an equivalent substitute.
• Apply the thread locker that came in the box. Manufacturers specify different grades for the armature bolt and the housing screws.
• Re check mounting hardware on a schedule. At least one manufacturer calls for a check every three months.
• Confirm the frame is actually rigid. A flexing or poorly anchored frame defeats a high force lock no matter what the label says.

How Is Holding Force Rated, and Does Door Weight Matter?

Holding force is the pull required to break the magnetic bond between the housing and the armature. It is not a weight capacity, and it is not related to how heavy the door is. The hinges or pivots carry the weight. This is the single most common misunderstanding among buyers specifying a maglock for the first time.

Published ratings describe either a dynamic load or a static one. A dynamic figure reflects a sudden impact, the kind of load a shoulder or a running push applies. A static figure reflects force applied gradually until the bond lets go. Manufacturers do not always state which they are quoting, so two units with the same number on the box are not necessarily comparable.

Treat the rating as manufacturer declared. Real world performance depends on three things the label cannot describe: whether the armature covers the magnet poles completely, whether the two faces are clean and flat, and whether the frame and door are rigid enough to transfer the load.

Which Bracket Do You Need: L, Z, U or Header Plate?

Bracket selection follows the swing direction and the frame profile, and brackets are usually specific to the brand and model of lock. Ordering a bracket from one maker for another maker's housing is a common wasted trip.

1. Outward opening door, deep frame stop. The magnet often mounts directly to the underside of the frame head with no bracket at all.
2. Outward opening door, shallow frame head. An L bracket offsets the magnet from the door face so the armature still lands squarely.
3. Inward opening door. An L bracket on the frame head carries the magnet, and a Z bracket carries the armature out to meet it.
4. Glass or frameless door. A U bracket wraps the top rail. Clearance is frequently the problem, and a purpose made glass door bracket or a shear lock is often the better answer.
5. Shallow or irregular header. A filler plate or angle bracket builds a flat mounting surface. At least one manufacturer sets a minimum header stop depth below which this is required.

How Much Power Does a Maglock Draw, and Should You Wire 12V or 24V?

Most commercial maglocks are dual voltage and run on direct current only. Voltage is selected on a jumper or a switch inside the wiring compartment, and some units sense the supply automatically. Check how the unit left the factory before you energize it, because the default is not always the voltage you are feeding it.

Current draw is modest. Published figures for common single door units sit in the low hundreds of milliamps, and the same lock draws roughly half as much at 24 VDC as it does at 12 VDC. That halving is the practical argument for 24 VDC on anything but a short run.

Two supply rules decide whether the installation behaves. The supply must be filtered and regulated, because alternating current riding on the direct current line is the usual cause of an audible hum at the lock. And the conductor has to be sized for the run, because a voltage drop that looks small on a meter shows up as a door that can be pulled open while the system reports it locked.

If you are planning the wider system, our access control and door hardware integration guide covers power supplies, voltage selection and how electrified devices share a supply. For strike wiring specifically, the electric strike schematic diagram shows the same circuit elements in a different configuration.

What Egress Rules Does an Electromagnetic Lock Have to Meet?

A maglock removes the mechanical link between the door hardware and the latch. Turning the lever or pushing the crash bar does nothing at all unless a switch inside that hardware cuts power to the magnet. That is the reason the model codes treat these locks as a special arrangement with prescriptive requirements.

Two release methods are recognised. Section numbers have been renumbered more than once, so cite the edition your jurisdiction has adopted rather than a number you remember.

What Does the Sensor Release Method Require?

The sensor release provision is the more prescriptive of the two. The lock unlocks on a signal from the egress side sensor and on loss of power to that sensor. Loss of power to the lock itself also unlocks it automatically.

• A manual unlocking device mounted 40 to 48 inches above the floor and within 5 feet of the doors, marked PUSH TO EXIT.
• Direct interruption of power when that device is operated, independent of any other electronics, holding the door unlocked for at least 30 seconds.
• Release on fire alarm activation and on sprinkler or fire detection activation, until the system is reset.
• Emergency lighting on the egress side of the opening.
• A listed locking system, which in recent editions means listing to the relevant access control standard.

What Does the Door Hardware Release Method Require?

Door hardware release is simpler. The hardware on the door leaf has an obvious operating method usable in any lighting, works with one hand, and cuts power the moment it is operated. Loss of power unlocks the door automatically. Where panic hardware or fire exit hardware is required on that opening, operating it has to release the lock as well.

The model codes do not require a fire alarm interface or an auxiliary push button for this method, which surprises people who have only ever installed sensor release systems. Neither method is permitted in high hazard occupancies.

Why Is Every Electromagnetic Lock Fail Safe?

A direct pull maglock holds only while current flows. There is no mechanical state in which it can stay locked without power, so fail secure operation is not physically available. Both release provisions also require automatic unlocking on loss of power, which makes the physical property a code requirement as well.

Delayed egress is a separate arrangement with its own code section, not a maglock feature. A delayed egress door holds for a defined period after an alarm sounds and then releases. Our guide to what delayed egress is and when code requires it covers that arrangement in detail.

Can You Put an Electromagnetic Lock on a Fire Rated Door?

Sometimes, and the conditions are strict. The lock has to be labeled for use on a fire door assembly, because every component installed on a fire door needs its own listing. An unlabeled lock on a labeled opening is a deficiency on inspection.

The point that catches people out is latching. A maglock is a holding device, not a latch, and it does not satisfy the positive latching requirement on a fire rated opening. The required latch stays, and it has to actually latch. Positive latching is what stops smoke pressure pushing the door open and carrying fire into the next compartment.

If you are working through hardware on rated openings, our commercial door fire rating guide sets out what each rating allows, and the OEM versus aftermarket parts guide explains how substituting a component affects a listing.

Why Is My Maglock Not Holding or Not Releasing?

Almost every maglock fault traces back to alignment, power or suppression. Work the table in order rather than condemning the magnet, because the coil itself is one of the least likely parts to fail.

Should You Fit a Diode or a Varistor Across the Coil?

Collapsing the field in a coil produces a voltage spike, and installers often fit a suppression component without checking what the lock needs. The choice changes release behaviour in a way that gets blamed on magnetism.

A flyback diode clamps at roughly one volt, so the stored energy bleeds away slowly and the magnet can keep holding the armature for a second or two after power is cut. A metal oxide varistor clamps far higher, so the energy dissipates much faster and the lock drops promptly. Diodes suit small solenoid devices such as strikes. For door magnets the varistor is generally the appropriate part.

Before adding anything, open the wiring compartment and look. Full size units frequently ship with suppression already fitted, and a second component in parallel is how a prompt lock becomes a sticky one. The common advice to degauss the armature or dimple the magnet face is not a fix, and risks damaging the machined surfaces.

When Is a Maglock the Wrong Choice?

Maglocks get specified because they are easy to fit and forgiving of door and frame condition. Those are real advantages. They also come with a code burden that an electric strike or an electrified lockset does not carry, and on some openings they are simply not the right device.

Choose something else when the opening needs positive latching that a magnet cannot provide, when the door is frameless glass with no bracket clearance, or when the cost of sensors, release buttons, emergency lighting and fire alarm interface outweighs the saving on hardware. Our comparison of an electrified mortise lock versus an electric strike works through the same decision from the latching side.

About the Author

Security Parts has supplied repair parts for commercial door hardware since 2001. We stock components at the part level for the brands locksmiths actually work on, and our diagram based lookup exists so a technician can identify a component before ordering rather than after. This guide was written by the Security Parts team from supplier documentation and the questions customers bring to us.

If you are maintaining a mixed estate, our commercial door hardware maintenance checklist covers the monthly, quarterly and annual tasks that keep electrified hardware working, and the commercial door hardware troubleshooting guide covers faults across exit devices, closers, locks and strikes.

Quick Answer

Security Parts stocks 29 replacement components for the LCN 4210 and 4210T Smoothee high security door closer series. The most frequently replaced parts are the three arm assemblies for the 4210 (EDA Arm, Cush Arm, Hold Open Cush Arm) and the track components for the 4210T. The cylinder assembly and metal security cover are handed and must be specified at order. Before ordering any part, confirm the model variant (4210 or 4210T), the hand, the cylinder size, and the finish. Closer adjustments are not accessible with the security cover installed -- the cover must be removed first. Call 845-935-0301 to confirm specifications before placing an order.

What Is the LCN 4210 Smoothee Series?

The LCN 4210 Smoothee Series is a heavy duty, high security surface-mounted parallel arm door closer built for correctional, institutional, vandal-prone, and high-traffic applications. It has passed 10 million cycles in independent testing and is tested and certified under ANSI Standard A156.4, Grade 1. The 4210 carries a ten-year warranty. The series includes a high-strength cast iron cylinder, a one-piece forged steel piston, a double-heat-treated pinion, all-weather hydraulic fluid, tamper-resistant regulating screws, and a high-efficiency full-complement low-friction bearing.

The LCN 4210 is a parallel arm push-side mount closer. The related 4510 is the hinge pull-side version. The 4210T is the track arm variant of the 4210, with a high security threaded track roller that cannot be removed without disconnecting the arm from the closer. All three share the same fundamental cylinder body but use different arm assemblies, covers, and accessories that are not interchangeable.

For a broader overview of LCN closer families stocked at Security Parts, see the door closers parts guide and the LCN 4000 series parts guide.

What Is the Difference Between the LCN 4210 and 4210T?

The 4210 and 4210T share the same cast iron cylinder body but use entirely different arm systems. Knowing which variant is installed determines which arm, cover, drop plate, and arm screw to order.

The model number is stamped on the closer body near the packing nut at the base of the pinion. Numbers such as "71" or "320G" found elsewhere on the body are manufacturing reference numbers and cannot be used to order parts.

Can I Access the LCN 4210 Adjustment Valves With the Cover On?

No. This is one of the most important service facts about the 4210 series and the detail most frequently overlooked. The LCN 4210 metal security cover uses four-point mounting precisely to resist tampering, and as a result, closer adjustments are not accessible with the cover installed. The cover must be removed before any regulation valve adjustment, spring power adjustment, or closer service can be performed.

On standard LCN series closers, the snap-on cover allows quicker access. The 4210 metal security cover is a different design and must be fully removed. Confirm the cover screw is the correct replacement (4210-31 for the 4210, 4210T-31 for the 4210T) when reinstalling after service.

What Torx Bit Size Does the LCN 4210 Use?

The LCN 4210 uses Torx fasteners as standard, which is one of its tamper-resistant features. The bit sizes required depend on the screw being driven.

LCN does not supply Torx wrenches with the closer. These are standard sizes that any professional installer will have available. If the installation uses the thru-bolt screw pack (4210-TBTRX), confirm the correct bit size for the specific fasteners in that pack before starting.

What LCN 4210 Parts Are Available?

All 29 LCN 4210 and 4210T Smoothee series replacement parts stocked at Security Parts are listed below. Parts for the 4210 and 4210T are noted separately. Several parts are shared between both variants.

Arm Selection: Which LCN 4210 Arm Do I Need?

Arm selection is the most common decision when ordering LCN 4210 parts. The 4210 offers three arm types for the standard parallel arm configuration. The 4210T uses a single track arm. The correct arm depends on whether a built-in stop, hold-open, or track configuration is required for the application.

What Is the LCN 4210 Extra Duty Arm (EDA)?

The 4210-3077EDA Extra Duty Arm is the default arm shipped with the 4210 closer. It is non-handed, solid forged steel, with a double slab arm-to-pinion attachment for maximum strength. The EDA arm does not include a built-in stop and is designed for potentially abusive installations. Because it is non-handed, the same part fits both left-hand and right-hand doors. It is UL listed for self-closing door applications.

If a door stop is needed on an EDA arm installation, it must be a separate overhead stop or wall stop device, not a CUSH arm accessory. Using a separate stop device alongside a CUSH arm installation is redundant and not recommended.

What Is the LCN 4210 Cush Arm (CUSH-N-Stop)?

The 4210-3077CNS Cush Arm is an optional handed parallel arm with a built-in stop in the soffit shoe. CUSH stands for Cush-N-Stop. When the door reaches its templated maximum opening angle, the arm contacts the stop in the shoe and arrests the door without any separate stop device.

The Cush Arm is forged solid steel with a double slab arm-to-pinion attachment. It is handed and must be specified left-hand or right-hand at order. Templated maximum openings are available at 85 degrees (A = 8-5/16 in., B = 9-5/8 in.) and 90 degrees (A = 7-11/16 in., B = 9 in.).

The drop plate (4210-18) is required for all Cush Arm installations. The CUSH shoe support (4210-30) is required when the frame reveal is less than 3-1/16 inches. The fifth hole spacer (4210-201) works alongside the CUSH shoe support. Order all three at the same time to avoid installation delays.

What Is the LCN 4210 Hold Open Cush Arm?

The 4210-3049CNS Hold Open Cush Arm provides both a built-in stop and a hold-open function in a single arm. A handle on the arm controls when the hold-open is engaged. Two important restrictions apply: the Hold Open Cush Arm is not available with the 4216 cylinder, and the Delayed Action cylinder option is also not available with the 4216. Confirm the cylinder variant before ordering this arm.

What Is the LCN 4210T Standard Track Arm?

The 4210T-3077T Standard Track Arm is the arm used on the 4210T track variant. It is handed with a large cross-section forged steel arm. The high security feature is the threaded attachment between the arm and the track roller (4210T-3034). The roller threads into the arm for extra strength and cannot be removed without disconnecting the arm from the closer body. The roller is included when the 4210T-3077T arm is ordered separately.

Metal Security Cover: LCN 4210-72MC and 4210T-72MC

The metal security cover is a standard component of both the 4210 and 4210T and is one of the distinguishing features of the Smoothee series. It uses four-point mounting for extra tamper resistance compared to two-point mounting on standard LCN series covers. The cover is handed and must match the finish of the installed hardware.

The 4210 uses the 4210-72MC and the 4210T uses the 4210T-72MC. These covers are different and cannot be substituted between the 4210 and 4210T. The cover is secured by the cover screw (4210-31 for the 4210, 4210T-31 for the 4210T).

An important service reminder: closer adjustments are not accessible with the cover installed. The cover must be fully removed before any regulation valve or spring adjustment. After service, reinstall the cover and confirm all four mounting points are secured with the correct cover screw.

Drop Plate, CUSH Shoe Support, Blade Stop Spacer, and Flush Panel Adaptor

Four accessories are required or optional depending on the frame conditions of the specific installation. These are frequently missed at order time and are among the most common causes of delayed installations.

When Is the LCN 4210-18 Drop Plate Required?

The 4210-18 Drop Plate has two trigger conditions.

• The top rail is less than 5-1/8 inches measured from the stop on a push-side mount.
• Any Cush Arm or Hold Open Cush Arm installation, regardless of top rail depth.

One dimension that every competitor misses: the plate requires a minimum top rail of 2 inches measured from the stop. If the top rail is less than 2 inches, the drop plate cannot be used. The plate ships with TORX screws. The 4210-18 is physically the same plate as the 4110-18, but the 4210-18 ships with TORX screws for high security mounting, while the 4110-18 does not. Do not substitute a 4110-18 on a 4210 installation.

The 4210T uses the 4210T-18 Drop Plate, triggered when the top rail is less than 5-1/4 inches, with a 2-1/4-inch minimum top rail required.

When Is the LCN 4210-30 CUSH Shoe Support Required?

The 4210-30 CUSH Shoe Support is needed when a Cush or Hold Open Cush Arm is installed and the frame reveal is less than 3-1/16 inches. The five-screw connection at the CUSH shoe is critical because the built-in stop generates significant force during the door arresting action. The CUSH shoe support provides anchorage for the fifth screw when the jamb depth is too shallow for a standard installation. Without it on shallow frames, the shoe will pull away from the frame under repeated use.

When Is the LCN 4210-419 Flush Panel Adaptor Needed?

The 4210-419 Flush Panel Adaptor is needed when the CUSH shoe must mount to a single rabbeted or flush frame that does not provide a horizontal mounting surface for the shoe. The adaptor creates the required horizontal surface.

When Is the LCN 4210-61 Blade Stop Spacer Needed?

The 4210-61 Blade Stop Spacer is needed when a 1/2-inch blade stop is installed in the frame. The spacer lowers the parallel arm shoe to clear the blade stop. Without it, the shoe contacts the blade stop before the door reaches its full intended opening angle.

What Does AVB Mean on the LCN 4210 Cylinder?

AVB stands for Advanced Variable Backcheck. It is an optional cylinder feature ordered with the suffix CYLAVB. On a standard LCN closer, backcheck begins at approximately 75 degrees of door opening, providing resistance against the door being forced or blown open. With AVB, backcheck starts at approximately 45 degrees, providing earlier and more pronounced resistance.

AVB is available on the 4210 series cylinder. It is useful in high-wind locations, on heavy-traffic openings where doors are routinely pushed open aggressively, or in any application where resistance at a lower opening angle reduces the risk of the door striking an adjacent wall or object. Specify CYLAVB when ordering the cylinder if AVB is required.

Can the LCN 4210 Hydraulic Fluid Be Refilled in the Field?

No. The hydraulic fluid in an LCN closer must not be refilled in the field. If a 4210 is showing signs of hydraulic fluid leakage, the appropriate response is closer replacement, not a fluid top-off. Attempting to refill the fluid voids the warranty and is explicitly stated as not permitted in LCN service guidance.

The all-weather hydraulic fluid in the 4210 performs without variation between -30 degrees F and +120 degrees F. This eliminates the need for seasonal closing speed adjustments that affect standard hydraulic closers. If a 4210 installation requires frequent speed adjustments as seasons change, the more likely cause is a seal or valve issue, not the fluid composition.

What Is the LCN 4210 Regulation Valve Adjustment Limit?

All LCN door closers have three regulating valves: General Speed (main closing speed), Latch Speed, and Backcheck. The 4210 follows this same three-valve design. LCN recommends not opening or adjusting the regulation valves more than 3 full turns from the shutoff position. Opening the valves beyond this limit can damage the seals and cause hydraulic fluid leaks. The regulation valve assemblies are staked to provide a physical warning when the screws approach maximum adjustment, but they do not mechanically prevent over-adjustment.

If the door does not latch after adjusting the latch speed valve, the solution is to increase spring power, not to open the latch speed valve further. Increasing the latch speed valve opening changes the closing rate but does not increase the closing force available for latching. Increasing closing force requires spring power adjustment on the Green Dial.

For step-by-step guidance on adjusting LCN door closer speed and spring settings, see the guide to adjusting a commercial door closer.

Does the LCN 4210 Require Periodic Maintenance?

Closers mounted according to LCN installation instructions require no periodic maintenance or seasonal adjustments. The all-weather hydraulic fluid handles the full operating temperature range without change to closing time. Monthly, quarterly, and annual visual inspections are recommended for Fire and Life Safety rated installations only. For those applications, inspection intervals should align with the applicable fire code schedule.

The practical implication for facilities maintenance staff is that a correctly installed 4210 in a standard application should not need routine service. If a 4210 on a routine installation is requiring frequent readjustment, that indicates an installation issue (incorrect spring size for the door weight, incorrect valve settings, damaged seal) rather than a normal maintenance need.

How Do I Read the LCN 4210 Date Code?

The LCN date code is a four-digit code found on the closer body. The first two digits indicate the week of manufacture and the last two digits indicate the year. A date code reading "2519" means the closer was manufactured in week 25 of 2019. This is useful when assessing whether a closer is within warranty, identifying when parts were last installed, or planning replacement schedules on a building's door hardware inventory.

Do not confuse the date code with manufacturing reference numbers such as "71" or "320G" that may appear stamped elsewhere on the cylinder assembly. Those numbers are internal references and cannot be used to order replacement parts.

Can a 4510T Track Be Converted to a 4210T Track?

Yes. The 4210T-3038 standard track and the 4510T-3038 track are physically the same track, with one difference: the 4510T includes a spacer bar that the 4210T does not use. To convert a 4510T installation to a 4210T, remove the spacer bar from the 4510T track and replace the metal cover with the handed 4210T-72MC cover in the correct finish. The 4210T and 4510T use different handed metal covers, so the cover cannot be reused from the 4510T. The 4210T-3034 track roller and the threaded arm attachment remain the same across both models.

This conversion is useful when an existing 4510T installation needs to change its mounting orientation from hinge pull-side to push-side parallel arm. The core cylinder and track can be retained; only the cover needs to change. Confirm the handing matches the new door swing before ordering the replacement cover.

LCN 4210 Screw Packs: TORX vs Thru-Bolt

The 4210 uses Torx machine screws as standard, not the SRT (Self Reaming and Tapping) screws used on most standard LCN closer families. Two screw pack options are available.

How Do I Order the Correct LCN 4210 Replacement Part?

Confirm each of the following before placing an order to avoid receiving a part that does not fit the installation.