SDC Quiet Duo™ Electric Latch Retraction for Exit Devices

As part of any electromechanical access control system or handicapped access, electrification of door hardware is required. Electrifying an exit device provides different options including controlling access, limiting access, and providing access and...


As part of any electromechanical access control system or handicapped access, electrification of door hardware is required. Electrifying an exit device provides different options including controlling access, limiting access, and providing access and egress when used in conjunction with a power door operator.

There are two ways to electrically configure an exit device - electrifying the exterior trim and equipping an exit device with electric latch retraction (ELR). Each method has its advantages and can be used to operate rim mount, mortise, concealed vertical rod, surface vertical rod and Less Bottom Rod (LBR) exit devices.

Electrifying the exterior trim provides the ability to remotely unlock the lock mechanism. This permits the lever or knob to be rotated, retracting the latch mechanism and then opening the door. Electrified trim requires a secondary action in order to open the door.

Installing electric latch retraction within the exit device retracts the pushpad and the latch mechanism, permitting the door to be opened. No secondary action is required. When installing a power door operator on an exit device-equipped door, the device must be equipped with electric latch retraction or an electric strike must be installed into the jamb.

Electric latch retraction has been installed into exit devices for many years. Early methods incorporated a powerful solenoid that would retract the latch mechanism. After a period of time, motorized latch retraction was introduced. Motorized electric latch retraction offers the end user several advantages including quieter operation, the ability to use an inexpensive power supply, and have a longer wire run between the device and the power supply using smaller gauge wire.

Electrically retracting the latch mechanism for longer than momentary operation has its advantages. A company can incorporate a timer mechanism, permitting access through an employee door that automatically unlocks the door, placing the device in passage mode on workdays at 7:45 a.m. and relocks the door the same day at 5 p.m.

This method limits access into the building during non-working hours. There is no need to install an access control system or provide employees with credentials. From 5 p.m. until 7:45 a.m., the door remains locked and no employee can gain access.

Using electric latch retraction is very similar to dogging an exit device. The act of dogging an exit device is to retract the latch mechanism and locking it in the retracted position. The action of retracting the latch mechanism places the door in passage mode.

Security Door Controls (SDC) has developed electric latch retraction kits for a number of bar/rail style non-fire rated panic/exit devices and fire rated devices.

Note: Before installing electrification onto a surface or concealed vertical rod exit device, be certain the device is in adjustment and operates smoothly.

For the purpose of this article, I was invited to observe the installation of the SDC LR100VDK Electric Latch Retraction Kit into a Von Duprin 98 exit device. The door is an employee entrance that leads into the warehouse. The door was equipped with a Von Duprin 98 rim exit device with mechanical dogging and lever trim.

The Von Duprin 98 rim exit device’s mechanical dogging mechanism rotates to capture the latch retraction rod when the pushpad is depressed, placing the exit device in the dogged or passage mode. The Quiet Duo Kit replaces the mechanical dogging assembly.

To install the Quiet Duo Kit, the two rivets securing the mechanical dogging assembly must be drilled out and the dogging assembly removed for those exit devices shipped after August 1997. Two screws secure the dogging assembly on previous models.

To begin the removal of the dogging assembly, remove the end cap, the cover plate and mounting bracket to gain access to the mechanical dogging assembly. Remove the dogging shaft and the dogging hook in order to expose both of the rivets securing the assembly. Once the rivets are drilled out, remove the dogging assembly from the case. Use a brush to remove any metal debris.

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