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Multi-function Doorways, Part One

December 26, 2011 access control / door hardware / Life Safety Hardware / security hardware
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As seen in Doors and Hardware Magazine.

Whenever something is invented, humans find more uses for it.  This is certainly true for door automation and electric locking.  It was not long after people realized a door could be unlocked remotely using an electric strike and a door could be opened automatically using a power operator (automatic door opener) that they began using these devices together.   Of course this combination of devices was soon interfaced with intercoms.  Exit devices with electric latch retraction and electromagnetic locks were thrown into the mix, as well as access control, delayed egress and/or security interlock systems.  Any of these systems alone is sufficient to complicate an installation, but when you start to use several on one opening, that’s when things really start to get interesting.

A hospital can be one of the best places to run into a doorway that needs to perform many functions (pun intended).  Hospitals seem to have more varied reasons to keep different people out at different times, or to let them in or out by different means.  In addition to standard life safety and security issues, hospitals also have to anticipate the needs of patients who may be under the influence of medication and/or mental disorders and/or have physical limitations.  Some patients must be kept inside for their own safety while all patients must be able to exit swiftly and safely in the event of a fire.

Let’s use as an example a hospital emergency ward entrance used primarily by ambulance drivers.  The hospital wants only ambulance personnel and the security guard  to be able to activate the power operator, and to control access by use of a remote switch operated by the security guard  for the general public and an access code by hospital employees (other than ambulance personnel).

Since it is a pair of doors, concealed vertical rod exit devices are the most efficient, safe and secure way to lock them and provide reliable free egress in the event of an emergency.  However, since there is a power operator involved, these devices must be equipped with electric latch retraction; and since use of the power operator was to be limited, a second electric means of opening the door would be required.

A simple way to solve the problem of the second means of unlocking is by using electrified exit device lever trim with one of the concealed vertical rod exit devices.  Persons not requiring the power operator can get in by using the access control, or the security guard  can “buzz” them in using one of two remote buttons.  Because there will be two means of unlocking the door electrically, the security guard  will need a small desk unit with two buttons:  one that activates the power operator and electric latch retraction and one that activates the electric exit device trim.

Below is an amateur wiring diagram (made by me) of how, basically, the system works.

Central to the concept is an access control device with two relays and a request to exit input.  This allows several of the connections to be made through the access control system.  If the access control system on site does not provide more than one relay, the same functions can be accomplished by using additional relays in the power supply.

The system as shown in my illustration above works like this:

Ambulance personnel activate the power operator using the access control system.  The access control system signals the power operator via contact closure in Relay #1.  The power operator triggers the relay in the power supply to retract the latches of the exit devices, then opens the door.

Other authorized hospital personnel use the access control system to unlock the lever trim.  The access control system changes the state of Relay #2, triggering the relay in the power supply to unlock the trim.  They turn the lever, pull the door open and walk in.

Injured people arrive on foot at the Emergency Room entrance.  The Security Guard sees them (or is notified by intercom, not shown) and lets them in by pressing the red button, activating the power operator, or by pressing the green button that unlocks the exit device trim.

There exist many possible variations of this system.  Knowledge of access control systems and door hardware are required, but the most important principal in play is the use of contact closure to signal multiple devices.


Exit Device Checklist

December 1, 2011 builders hardware / door hardware / hardware sales wars / Life Safety Hardware / security hardware
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See also Exit Device Basics

Here are a few questions you need to be able to answer before you order exit devices:

  • Is the door made of wood, hollow steel, Fiberglas, aluminum and glass, or all glass?
  • Is the door is fire rated or non-fire rated?
  • Door width if single door or pair of doors with center mullion?
  • Door width and height if for a pair of doors without mullion?
  • Door thickness?
  • Exit device finish?
  • Will this be an exit-only device, or will there be outside trim?
  • If there is outside trim, what function is it?

It will save you time and aggravation if you know the answers to these questions before you call your hardware vendor.

You may also want one or more of these or other mechanical options:

  • Cylinder dogging (not available on fire rated devices)
  • Less bottom rod (for vertical rod exit devices)
  • Double cylinder (trim locked or unlocked from inside secured space)

There may also be electrified options:

  • Does the exit device need to have electrified trim?  If so, fail safe or fail secure?
  • Does the exit device need to have electric latch retraction?
  • Does the exit device need to have push pad or latch monitor switches?
  • Do you need a delayed egress exit device?

Save time and money by gathering the necessary facts before shopping for exit devices.

Interconnected Locks

October 28, 2011 builders hardware / door hardware / Life Safety Hardware / security hardware
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Sargent 7500 Series Interconnected Lock

An interconnected lock is actually two locks that are connected by an assembly that retracts both the deadbolt and the latch simultaneously when the inside handle is turned.   This is done to fulfill the life safety requirement under NFPA 101 that egress should be accomplished by one motion with no prior knowledge necessary, and at the same time provide the user with the security of a deadbolt.  The same function could be provided by an entry function mortise lock, but interconnected locks are cheaper, since they are usually cobbled together out of (usually) a grade 2 cylindrical lock and a tubular deadbolt.

The history of the interconnected lock is a twisted, strange story of different companies reinventing the wheel with different distances between the centerlines, connected or separate latch/bolt assemblies with correspondingly different strike preps, and radically different hole patterns on both interior and exterior door surfaces.  The end result has been many, many doors and frames prepped for locks that are now irreplaceable.

Today, preps are much more standardized.

These are some of the interconnected locks available today and the measurements of their preps:

  • Falcon H Series – 4 inches CTC, 1-3/4 inch hold above, 2-1/8 inch hole below
  • Schlage H Series – 4 inches CTC, 1-1/2 inch hole above, 2-1/8 inch hole below
  • Schlage S200 Series – 4 inches CTC, 1-1/2 inch hole above, 2-1/8 inch hole below
  • Schlage CS200 Series – 4 inches CTC, 2-1/8 inch holes above and below
  • Sargent 75 Series – 4 inches CTC, 2-1/8 inch holes above and below
  • Yale 4800LN series – 4 inches CTC, 2-1/8 inch holes above and below

Replacing any of the locks above with any of the others would not present an enormous problem.

 

Sargent 7500 Series Door Prep

PS900 Series Schlage Electronics and Von Duprin Power Supplies Demystified

September 27, 2011 access control / door hardware / Life Safety Hardware / security hardware
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Von Duprin and Schlage Electronics are divisions of Ingersoll Rand. Both are major manufacturers of power supplies for use with electric locking systems and access control. As of January 1st, 2011, Ingersoll Rand discontinued two of their power supply product lines, the PS800 series Von Duprin and the Schlage Electronics 500 series, and merged them into the new PS900 series.

A split in power supply branding may or may not remain, depending on what document you are looking at, but whether they say they are Schlage or Von Duprin, they are all the same PS900 series.

Here is the lineup:

PS902 – 2 Amp output at 12 or 24VDC, field selectable

Compatible with these option boards:

  • 900-BBK: Battery Backup – back up power in case of power outage, includes batteries
  • 900-FA: Fire Alarm – relay for interface with fire alarm panel  – wires to main board
  • 900-2Q: 2 Relay QEL control Board – to run 2 Von Duprin QEL devices
  • 900-4R: 4 Relay Output Board – four relay outputs to operate 4 electric locking devices, not QEL or EL
  • 900-4RL: 4 Relay Logic Board – for man trap or security interlock systems or up to 4 QEL devices
  • 900-8F: Fused 8 Zone Distribution Board – 8 outputs, fused for circuit protection
  • 900-8P: PTC 8 Zone Distribution Board – 8 outputs, circuit breaker protected

PS902 can accommodate 1 of the above option boards in addition to the 900-FA option and battery backup.

For use with electric locks and with Von Duprin Quiet Electric Latch retraction (QEL) exit devices, but NOT with Von Duprin electric latch retraction (EL) exit devices.

PS904 – 4 Amp output at 12 or 24VDC, field selectable

Compatible with these option boards:

  • 900-BBK: Battery Backup – back up power in case of power outage, includes batteries
  • 900-FA: Fire Alarm – relay for interface with fire alarm panel  – wires to main board
  • 900-2Q: 2 Relay QEL control Board – to run 2 Von Duprin QEL devices
  • 900-4R: 4 Relay Output Board – four relay outputs to operate 4 electric locking devices, not QEL or EL
  • 900-4RL: 4 Relay Logic Board – for man trap or security interlock systems
  • 900-8F: Fused 8 Zone Distribution Board – 8 outputs, fused for circuit protection
  • 900-8P: PTC 8 Zone Distribution Board – 8 outputs, circuit breaker protected

PS904 can accommodate up to 2 option boards and battery back up.

Note:  no plug-in for fire alarm relay on main board.  900-FA is only usable with the PS904 if used with an option board.

For use with electric locks and with Von Duprin Quiet Electric Latch retraction (QEL) exit devices, but NOT with Von Duprin electric latch retraction (EL) exit devices.

PS906 – 6 Amp output at 12 or 24VDC, field selectable

Compatible with these option boards:

  • 900-BBK: Battery Backup – back up power in case of power outage, includes batteries
  • 900-FA: Fire Alarm – relay for interface with fire alarm panel  – wires to main board
  • 900-2Q: 2 Relay QEL control Board – to run 2 Von Duprin QEL devices
  • 900-2RS: 2 Relay EL Control Board – to run up to 2 Von Duprin EL devices
  • 900-4R: 4 Relay Output Board – four relay outputs to operate 4 electric locking devices, not QEL or EL
  • 900-4RL: 4 Relay Logic Board – for man trap or security interlock systems
  • 900-8F: Fused 8 Zone Distribution Board – 8 outputs, fused for circuit protection
  • 900-8P: PTC 8 Zone Distribution Board – 8 outputs, circuit breaker protected

PS906 can accommodate up to 3 option boards, fire alarm interface (with option board) and battery back up.

For use with electric locks and with up to 6 Von Duprin Quiet Electric Latch retraction (QEL) exit devices, but NOT with Von Duprin electric latch retraction (EL) exit devices.

PS914 – 4 Amp output at 12 or 24VDC, field selectable

Compatible with these option boards:

  • 900-BBK: Battery Backup – back up power in case of power outage, includes batteries
  • 900-FA: Fire Alarm – relay for interface with fire alarm panel  – wires to main board
  • 900-2Q: 2 Relay QEL control Board – to run 2 Von Duprin QEL devices
  • 900-2RS: 2 Relay EL control Board – to run up to 2 Von Duprin EL devices
  • 900-4R: 4 Relay Output Board – four relay outputs to operate 4 electric locking devices, not QEL or EL
  • 900-4RL: 4 Relay Logic Board – for man trap or security interlock systems
  • 900-8F: Fused 8 Zone Distribution Board – 8 outputs, fused for circuit protection
  • 900-8P: PTC 8 Zone Distribution Board – 8 outputs, circuit breaker protected

PS914 can accommodate 2 of the above option boards, plus fire alarm interface (on one of the boards) and battery back up.

Capable of powering:

  • Up to 4 Electric Latch retraction (EL) exit devices with 900-4RL board
  • Up to 2 EL devices with 900-2RS board
  • Up to 4 Quiet Electric Latch retraction (QEL) exit devices
  • Up to 4 Chexit (CX) delayed egress exit devices off the main board (use 900-8FA combination board if Fire Alarm relay is required)
  • Electric locks or strikes

 

Ordering Tips:

PS-914 is a 4 Amp power supply that is double the capacity of the old PS873, however, from my conversation with IR tech support, their feeling is that it is prudent to power no more than 4 EL devices per PS-914.  Theoretically the power supply could support as many as 8 EL devices however this presents the challenge of timing the relays so that no two can change states at the same time.  If two EL devices are powered up simultaneously the PS-914 could be damaged.

None of the PS900 series power supplies are a drop-in replacement for their predecessors, and the old and new option boards are not cross-compatible with the old and new power supplies.  Therefore, replacing old power supplies with new can present a rewiring challenge.

Ordering back-up batteries can be a little tricky, since they have very similar part numbers for the batteries, the charging circuit board, and a set that includes the board and the batteries.

  • 900-BAT – Pair of batteries only
  • 900-BB – Battery back up board only
  • 900-BBK – Power battery back up kit, board and batteries

 

 

The “Passage Set”

September 9, 2011 builders hardware / door hardware / hardware sales wars / Life Safety Hardware
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Often, when customers say they want a “passage set” they really want a cylindrical lock that actually locks.  This is because they don’t know (and often don’t want to know) cylindrical lock functions.   Therefore, the next question I ask is often, “How do you want this ‘passage set’ to work?”

Of course, “passage set” is the name of a cylindrical lock function.  The function of a passage set is that the latch can always be retracted by turning either handle.  It always latches but is never locked.   So when customers order a passage set with an electric strike, I am doubly suspicious.  Do they really want a passage set with that electric strike?

Passage sets are used in non-locking applications like corridors, closets and some offices, and in non-locking fire rated doors to meet the positive latching requirement for fire rated openings.

Therefore, if you want to sound intelligent as you order your cylindrical locksets, don’t call them passage sets unless they are.  Thank you.

 

Avoiding Tailpiece Loss Syndrome

August 26, 2011 builders hardware / door hardware
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SFIC Tailpieces, A.K.A. Throw Members

Tailpiece Loss Syndrome is such a common occurrence in the door hardware industry that it is almost a joke.  It happens like this:

  1. The job specifies small format interchangeable core (SFIC) cylindrical locks
  2. The locks are shipped with separate tailpieces, often called ‘throw members’
  3. The installer (usually a contractor) installs the locks and throws the tailpieces away

This occurs so often that when I get a call from a customer who says, “I have a job where we installed all SFIC cylindrical locks…”  I finish the sentence for them, “… and the contractor threw the tailpieces away.”   That usually gets a chuckle, but there’s not much humor in it really, especially if the tails must be factory ordered with a lead time of several weeks and the inspection is tomorrow.

Nope, no fun.

To avoid losing the tailpieces this way, there are a couple of things you might do:

  • Get a responsible person (maybe you) to collect the tailpieces when the locks are delivered, or
  • Have the tailpieces shipped separately directly to you, or
  • Order cores with the locks and have the contractor install them and ensure they are working properly.  (They will need to have the tails to accomplish this.)

If you elect to order the cores with the locks and want to avoid the delays associated with waiting for an order of master keyed permanent cores, order construction cores.   Construction cores are temporary cores that are all keyed alike for use during the construction phase.  Typically hardware re-sellers stock construction cores or they are readily available from the factory, so they are usually deliverable fairly quickly.

 

Locking People In

August 12, 2011 access control / door hardware / Life Safety Hardware / security hardware
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I often get a request to help create a system that locks people in.  People want to lock children inside a daycare center, students inside a “Time-Out” room, babies inside a nursery in a maternity hospital or patients inside, for example, an Alzheimer’s disease in-patient facility for their own good.

“Well, what if there’s a fire?” I ask.

That’s really the issue.  If we are keeping them in, how are they supposed to get out in the event of a fire?  Yet, except when there is a fire or other emergency that renders the building unsafe, it is in their best interest if they are kept inside.

Often, people simply want to lock people in with an electromagnetic lock or other device.  Since this is certainly a violation of life safety code, any injury that may result would be uninsurable and could invite litigation.

I discuss delayed egress systems in depth in another article (click here to read).     A delayed egress system is really the right way to do this, since it is actually covered in the NFPA 101A Special Locking Arrangements section of the fire safety code, but it is fairly inconvenient to use.  To get out without setting off an alarm users must use some kind of bypass request to exit switch like a keypad, card reader or key switch – much less convenient than, say, simply pushing a door open via the push pad on an exit device.

The gist of a delayed egress system is that, after a short ‘nuisance’ delay, the lock sounds an alarm for fifteen seconds and then lets the person out.  That means that authorities on the secured premises have fifteen seconds to get to the exit and prevent unauthorized egress.

Where unauthorized egress is not a life threatening prospect, therefore, a delayed egress system is perfectly adequate.  However, when a person’s life may depend on being kept inside their care facility, a more complex solution maybe required.

A great solution for Alzheimer’s or other dementia care facilities is the WanderGuard system by Stanley.  This system is designed for Alzheimer’s and other health care facilities where unscheduled patient departure is an issue, and covers other needs with fall monitoring and patient call capabilities.  Patients are fitted with bracelets that serve as tracking and communication devices.  As one might expect, such a system is not inexpensive and a bit on the overkill side for use in a day care center or maternity facility.  To physically keep people inside the facility, the WanderGuard system is designed to interface with delayed egress locks.

I think that the WanderGuard system would be a good choice for use in maternity ward nurseries as well.

The situation is more challenging when you have a day care center or a “Time-Out” room.

I had heard that Schlage was coming out with a mechanical time out lock, but a search as of today renders only the same Time-Out Room solution:  An electromagnetic lock with a momentary pushbutton.  The troublesome child is forced into a room, the door is shut, and then the teacher or other disciplinarian must physically press the momentary contact pushbutton to keep the magnetic locked locked.  As soon as the teacher lets go, the child is free.

As long as the button is momentary, I have no problem with this idea.  Should there be a fire or other life safety emergency, even if the teacher panics and runs away, leaving the child in the Time Out Room, the child will still be able to leave the room and exit the building.

The right way to prevent the kids in a daycare center from running out of the building and into the street without permission is with a delayed egress system.  True, it may be cumbersome to punch in a code on a keypad or present a proximity card for authorized egress, but delayed egress systems can be easily deactivated for periods of time, say, for drop off and pick up.  A delayed egress system is more expensive than, for example, an electromagnetic lock connected to the fire alarm system for safety.  But if you run the scenario of a fire in your mind, the fire alarm interface to the electromagnet malfunctions, panicked children and day care providers flinging themselves against an illegally locked door, too crazed with fear to think – suddenly a delayed egress system makes a lot more sense.

There is really only one place you can really lock someone in, and that’s in a jail or prison.  Otherwise there must be some provision to let them out – for safety’s sake.

 

How to Choose a Door Closer

July 8, 2011 builders hardware / Door Repair
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To intelligently choose a door closer for your application you have to know certain facts:

  • Does the closer need to comply with ADA opening force guidelines?
  • Is the door an interior or exterior door?
  • What is the door width?
  • Will the closer be mounted on the push or pull side of the door?
  • Where on the door will the door closer be installed?  How much room is there?
  • Are there any special circumstances like wind, positive or negative pressure, etc.?
  • You may also need to know the door handing.

ADA Reduced Opening Force Guidelines

American Disabilities Act (ADA) reduced opening force restrictions are enforced by the Authority Having Jurisdiction in your locality.  In some localities or applications ADA requires a maximum opening force of 5 lbs. and in others a maximum opening force of 8.5 lbs.  Most closers on the market today can be field adjusted to comply with these restrictions, but to do so you need to have a door pressure gauge.

I am mildly acquainted with two door pressure gauges.  One is the model DPG by HMC and the other is the ADA/FG by LCN.  Apparently there are a lot of initials involved in door pressure.

Door closers are also available with reduced opening force meant specifically to comply to ADA standards.

Manufacturers usually print a disclaimer that says that a door closer adjusted to ADA maximum opening force may not have enough power to shut the door.  This is often true because perhaps recommended spring strengths for different applications are the result of perhaps a century of innovation.  Manufacturers know that a force greater than 8.5 pounds may be necessary to close a door.

Interior versus Exterior

When speaking about door closer closing force, we say that a door closer is of a certain size.  Door closer size does not refer to actual dimensions, but to spring strength.  Historically, door closers are available in sizes 1 through 6 – 1 being the wimpiest and 6 capable of exerting the strongest closing force.

A size 4 closer is usually recommended for an exterior, 3-foot wide door, whereas a size 3 closer is deemed appropriate for an interior door of the same dimensions.  The assumption here is that the exterior door is more likely to be expected to close a door against a wind or negative or positive air pressure.

Door Width

If you look at a door hung on butt hinges and equipped with a door closer from above, it looks something like this:

View from the Ceiling

 

You see from the illustration that the door closer closes the door by exerting force on a point about eight or ten inches from the hinge side of the door.  To see what this means, go to a door with no door closer.  Open it.  Now put your hand a foot from the hinge side of the door and push it closed.  Pretty difficult, isn’t it?   If your door was wider, it would be even harder to close from that point.  This is why door closer size – that is, spring strength – is determined by the width of the door rather than the height.

For a three foot wide exterior door, you would normally adjust your door closer to be a size four.  For a four foot wide exterior door you would adjust your door closer to be a size five.  Therefore, if you have a four foot wide exterior door, you had better buy a closer that can be adjusted to a size five.

Push or Pull?

Different arms are required for different applications.  On doors that swing out, where the closer is mounted on the push side, the closer is mounted in a top jamb or parallel arm configuration.  If it is mounted on the pull side it is mounted in what is called a ‘standard’ installation.  (There are other ways to mount a closer on the push side, but parallel arm and top jamb are the most common.)

See manufacturer’s literature for more information, or check out my article on Door Closer Basics.

Room

If you have a glass and aluminum storefront kind of door, you may have a space issue as regards your choice of door closer.  If you have a hollow metal door with no window hung in a steel frame, chances are you will have no space issue.

You need to figure out what door closer will fit.  To do that, measure the space where you would like to install it and download installation templates or instructions from manufacturer’s web sites.  Check the dimensions to see if the closer you have selected will work or not.

Or you can measure your door and frame and consult a door hardware professional.

Special Circumstances

I have installed door closers in some fairly challenging environments.  One, for example, was on a four foot wide, eight foot high, two and a quarter inch thick mahogany and glass door.  In addition to the size of the door, the location was also challenging – right across Beacon Street from the Boston Common where the wind could race across the open ground and dash itself against the door to its heart’s content.  Also, the front of the building had settled over the century or so of its existence, and leaned decidedly inward.  The door opened inward, and, left on its own, would swing sedately inward to 90 degrees if not latched.

In other words I had to install a door closer that would close an extra heavy door, uphill, in a wind.  I actually got one that would do it about 95% of the time.  For this application I chose the most durable, powerful, adjustable door closer I knew at the time:  the LCN 4041.  If I did the same job today I would probably choose an LCN 4011 or a Norton 7500.

A big, beefy, versatile door closer is not a cure-all.  For example, sometimes the 4041 is just too big, or templated too close to the hinge.  The point is that you must look at all the details of your door before you buy a door closer – not only how it is made and its size, but its environment as well.

 

What’s Hot in Door Hardware

June 18, 2011 access control / door hardware / security hardware
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A couple of new innovative products have recently caught my attention.  Here they are:

Security Door Controls (SDC) Model LR100VDK:

Field Installed Electric Latch Retraction Retrofit Kit for Von Duprin Exit Devices

 

 

 

 

 

 

 

 

This product is available now.

http://www.sdcsecurity.com/whatsnew2.aspx#lr100

The mere 450mA inrush powering Security Door Controls’ new electric latch retraction retrofit kit is attractive enough.  Its compatibility with all Von Duprin touch bar style devices may make it just about irresistible.   Optional request to exit switch kits are available.  The unit is usable for access control and electric dogging applications.

The small inrush is huge.  (I always wanted to say that.)  High inrush electric latch retraction requires special, expensive power supplies.  Not so with the LR100VDK.  Your average regulated and filtered 1-amp 24vdc power supply will do nicely, thank you.

Another great aspect of this kit is that it is compatible with the Von Duprin 22 series exit device. So now, for relatively short money you can give a customer electric latch retraction in a decent quality exit device.

HES Model 8500 Electric Strike for Mortise Locks


http://www.hesinnovations.com/en/site/hesinnovations/Products-startpage/?groupId=141798&productId=764670

This product is due to become available by the end of August, 2011, but we’ll see.

Hanchett Entry Systems’ new lipless electric strike solution for mortise locks.

Installing an electric strike to release a mortise lock will be much easier with the HES 8500 since no cutting of the face of the frame is necessary.  Below is an illustration showing the difference between the HES 1006 standard electric strike for mortise lock and the new HES 8500.

HES 1006 prep for hollow metal

HES 8500 door prep for hollow metal - look ma, no lip!

 

 

 

 

 

 

 

 

 

 

 

 

This is not a new idea, but installers seem excited about the prospect of having an alternative to the Securitron UnLatch, which has been around for quite some time.  The Unlatch model that the HES 8500 will compete with will be the Securitron MUNL.

Of course, the advantage the MUNL currently enjoys is that, unlike the 8500, one can actually buy an MUNL.  Comparatively, the Securitron requires a door frame depth of about 1-7/8 inches whereas the the 8500 will require about 1-3/8 inches.  The 8500 will draw 240mA at 12 volts DC and 120mA at 24 volts DC and draws no inrush current.  The MUNL has an inrush of 2 amps at 24vdc or 4 amps at 12vdc and an operating current of 600mA at 12vdc or 300mA at 24vdc.  One important result of the lower current consumption of the 8500 will be that instead of the 4 amp 12vdc or 8 amp 24vdc power supply necessary for each MUNL, one 8 amp 24vdc power supply will theoretically power as many as perhaps 60 of the new HES 8500.  Of course then, factors like wire run will come into play, but still.

Another positive attribute will be that the 8500 will be field selectable for fail safe or fail secure whereas the MUNL requires an additional module to make it fail safe.

All in all, the 8500 seems that it will be a better choice all around.  We’ll just have to wait and see how it performs in the field after it becomes available at the end of August 2011.

Low Voltage Detective Work

June 4, 2011 access control / door hardware / Life Safety Hardware / Lock Repair / security hardware
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Finding the Current Drop

 

As electric locking systems become increasingly complicated, troubleshooting these systems has also become more complex.  Yet certain basic principles always apply.

Case in point, a customer had access control on a stairwell door using a fire rated mortise exit device with an electrified mortise lock.  The solenoid in the mortise lock had burned out twice and the third one, newly installed, was already too hot to touch.  Granted, a solenoid operated fail safe device used in a continuous duty application will get warm, but it should not get too hot to touch.  So they called me to help them figure out what was going on.

To find the problem, I first listed the possibilities:

  1. They had gotten three defective solenoids in a row
  2. The power supplied is the wrong voltage – if the voltage was either too high or low, that would cause the solenoid to heat up
  3. The current supplied is inadequate – the solenoid used 330mA.  If it were being supplied with only 150mA, for example, the solenoid would heat up.

We determined that 27 volts DC was available at the door to power the 24 volts DC solenoid – perfectly acceptable – and we all felt that it was rather unlikely that they had received three defective solenoids in a row.  So that left current drop.  Where was the current going?  What was preventing it from getting the current it needed?

The access control tech on site could not determine whether the solenoid was getting enough current at the door by using a meter (for whatever reason) so we traced the current back through the line.

The power supply was a 6 amp, 24 volts DC power supply that had an output board with 8 fused outputs.  If all were in use, then a max of 750mA should be available from each output, provided they all were carrying the same amperage load.  We determined that four of the outputs were being used:  three were used to power electric strikes at 300mA and one was used to power the electric mortise exit device at 330mA.  The sum of the current draw for all devices attached to the power supply was therefore about 1.2 amps – well within the power supply’s capacity.  Therefore the power supply size was not the problem.  The technician measured the output from the contacts that were connected to the mortise lock and found that they were outputting correct voltage and current.  Therefore the output board was not the problem.

Assured by the technician that the wire run between the power supply and the mortise lock was less than 100 feet and that 18 gauge wire was used, I knew that the wire run was not the problem.  I asked how power got from the door frame through the door and into the mortise lock.  The technician responded that power transfer was accomplished by use on an electric hinge.

Typical wire gauge in an electric hinge is 24 gauge – a thin wire to be sure, but since power only needs travel a few inches through it, hinge wire gauge is usually not a problem.  But this electric hinge had its own 3-foot wire lead threaded through a raceway in the door to the mortise lock.  Whereas a few inches of 24 gauge wire might not be a problem, I reasoned, three feet of it might be a problem.  We talked about it briefly and then agreed that they would give it a try.

To my dismay, they called back two hours later – after they had replaced the wire running through the door with 18 gauge wire and let the mortise lock run on it for a while – and let me know that this did not work either.

The answer finally came when I asked how the electric mortise lock was connected to access control and was told there was a controller in a box above the door.  The controller used a form C relay to turn the electric mortise lock on and off.  I suggested that the technicians check the relay to make sure it was working properly.  When they did they discovered that the electric mortise lock had been connected in series with another device.  This other device – whatever it was – drew enough current to deprive the mortise lock of the current it needed to operate without burning up.  Problem solved.

The moral of the story is that, yes, access control has only gotten more complex as time goes by, but by using simple, logical methods a good technician and figure out and repair most problems.  So stick with it and keep asking questions until you ask the right one.

 

And good luck!

 

 

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