Electric Latch Retraction Secures Pair of Doors

We were asked to bid on adding access control to a pair of doors owned by a local municipality. The doors were added with the intention of controlling pedestrian traffic around the building where individuals were congregating and otherwise occupying city property outside.

We missed bidding on the door installation, but were happy to have an opportunity to bid the access control.

The basic requirements of the access control and locking systems were:

  • Use as much of the existing door hardware as possible
  • Enable the doors to electrically dog on schedule, and other times to be electrically unlocked for access using a new card reader connected to their existing electronic access control system.
  • Be the low bidder

I surveyed the doors and initially failed to identify the hardware properly, mistaking the existing devices for another model. When I tried to spec out an EL upgrade for the bars, I was informed that an electric latch retraction (EL) upgrade was not available and both exit devices would have to be replaced with a different model which did have an EL upgrade available. I took a second look at the bars and realized my error.

Fortunately, the error was in both my and the customer’s favor, because First Choice, the correct manufacturer of the exit bars, actually did offer an EL upgrade option. This meant we could re-use the existing exit devices which were essentially brand new.

To keep the materials cost low while providing a vandal-resistant solution, I specified a electrified hinge rather than another type of power transfer. Hinges fit into the existing door/frame prep, are concealed when the door is closed, and are inconspicuous when the door is opened.

Care must be taken to get the correct flange and span hinge, the correct gauge and number of wire conductors and of course the correct architectural finish.

As is the case with most ELs, power requirements for the EL solenoids must be calculated, then wire gauges and equipment locations must be selected accordingly. Improper conductor sizes, or excessively long wire runs will contribute to unacceptable EL operation if the ELs do not get the power they require to unlock.

Our installation included installing and wiring the power supply of the ELs, the electric hinges, the card reader, and connecting the reader and door hardware to the access controller.

First Choice recommends using the following gauge wire for different cable runs between the power supply and the door:

When an Electrified Hinge is used:

  • 14 AWG - 40 ft max
  • 12 AWG - 60 ft max
  • 10 AWG - 100 ft max

Where an EPT is used:

  • 14 AWG – 75ft max
  • 12 AWG – 80ft max
  • 10 AWG – 125ft max

The EL kit is furnished with illustrated instructions. The operation involves removing two sub-assemblies inside the device; cutting a rod down, and installing one new mechanical assembly and the solenoid.

Once the head cover and push bar have been removed, the exit device can be removed from the door in order to work on it. The rim version of the device is attached to the door with four screws. This upgrade involved removing four screws on the back of the device.

A fresh Phillips tip may prevent you damaging the screws trying to extract them.

Next a rod which extends from the latch to the hinge end of the device, referred to as the trim connecting rod, needs to be shortened a little, and I did this without removing the rod from the device with a Dremel tool and cutoff wheel attachment.

Mounting the bracket and the solenoid are straight forward and simple. No delicate adjustments were required on my bars.

The instructions emphasize a 1/8” space be maintained during assembly of the solenoid plunger to a bracket. I used a drill bit as a gauge.

If your bar has a rim cylinder, be sure to time the key position on the cylinder when assembling, and test that the key retracts the latch and also that the key can be removed from the cylinder before you do the final assembly.

Also keep in mind that the First Choice power supply outputs which connect to the solenoids are DC volts. The solenoid/module assemblies are polarity sensitive, and the output circuitry in the power supply senses the solenoids’ presence and position (connected and not energized) when you complete the connections and apply line voltage to the power supply line voltage input connections.

In order to unlock both of the bars, the input terminals in the power supply must be interconnected. Since I was using two exit devices on one opening, I had to bridge between Input 1 and Input 2 and provide a single Normally Open dry contact output from my access control device. LEDs on the power supply help you determine what’s going on if you hit a snag. It is a very robust power supply.

Since there are rare occasions when exit devices must unlock in the event of a fire alarm, the power supply is equipped with FACP (Fire Alarm Control Panel) interface terminals. If you are not connecting the power supply to a FACP, place a wire jumper across the FACP terminals in order for the power supply to work correctly.

Our door also had a First Choice removable mullion into which the two exit devices latched.

 

Equipment List

First Choice EL3000 Upgrade: The EL3000-1 is available as a retrofit kit for existing devices that have not been cut down from standard sizes. (Consult First Choice for more information.) Modification of the existing exit device will require some component alteration and replacement. More Info: www.firstchoicebuildingproducts.com.

PSEL3000 Power Supply: SP-1000 will operate up to two (2) 24VDC panic hardware devices simultaneously. It is designed to handle the high current surge panic hardware locking devices demand. Each lock output has an adjustable relock delay timer. It will control a pair of doors simultaneously or independently control two individual doors. It has a follower relay for each output to trigger external relays, ADA push plate switches, etc. Delayed follower relays control automatic door operators for doors that are always locked or for doors that are unlocked during the business day. In addition, two un-switched auxiliary voltage outputs are provided for powering card readers, keypads, REX PIRs, electronic timers, relays, etc. A programmable FACP interface will either provide power or remove power to the lock outputs when activated.

Marray Power Transfer Hinges: The Marray PTH (power transfer hinge) offers several advantages to the installer/customer Two of the wires are heavy 18 gauge, silver coated, high conductivity Teflon jacketed conductors and four of the wires are 28 gauge, silver coated high conductivity conductors. The two 18 awg wires can be used with electric latch retraction devices. In fact, this EL hinge was engineered for just such uses. The smaller 28 awg wires can be used for controls and switches.

According to Marray, not only is this PTH (Power Transfer Hinge) stronger and able to withstand more inrush than any other electric hinge on the market, but it has also independently tested to over 800,000 cycles on average before a wire breaks or goes to ground. (That is 8 times the UL requirement of 100,000 cycles.)

This hinge is also burn tested and UL10C listed for use on fire rated doors and frames. Marray was the first with such a listing.

Marray is the designers and trade name holder of the Perfect Raceway Program. This program allows for Certified Personnel who complete the Intertek class program, to drill fire rated doors in the field for the installation of access control locking hardware. Visit this page for more information on the Perfect Raceway Program. More Info: www.marray.com.

Door Controls International Door Closers: There were no door closers on the doors so we sold them two for these doors. We used cost effective Door Controls Premium #4000 Series closers from Door Controls International. They are ANSI A156.4 Grade 1; UL10C with lifetime warranty. More Info: www.doorcontrols.com.

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