Electric Latch Retraction Secures Pair of Doors

The customer wanted to re-use existing door hardware, while adding a new card reader connected to an existing access control system. An electric latch retraction upgrade for the exit bars was a key component of the plan.

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.

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