Von Duprin Commercial Door Hardware

Converting Mechanical Exit Devices to Electrical: Electric Latch Retraction

Electric latch retraction, an optional feature on many models of exit devices (panic bars) may be known by a number of names.  It is sometimes referred to in the industry as “remote dogging” or “latch pull back.”  All of these terms refer to the ability of a particular exit device to lock or unlock according to power supply.

To understand how electric latch retraction works, it helps to first get an idea of how a regular (mechanical) exit device works.  An exit device consists of a bar which extends across the width of the interior side of a door. It may be a crossbar (raised, arm-style) or it may be a flat, push bar.  The bar is connected to a rod, which may be concealed (mounted inside the door) or exposed (mounted on the outside of the door’s interior side.)

The exit device renders the door locked.  It cannot be opened from the exterior except with a key.  From the inside, the door can be opened quickly and easily by simply pushing on the bar.  As soon as the door closes, it re-locks automatically.  Exit devices are sometimes referred to as “panic bars” because they are much easier and quicker to open in an emergency situation (i.e. fire) than a knob or lever.  In fact, most building codes in the industrialized world mandate that doors on public buildings cannot be locked from the inside except with the use of a panic bar.

Ordinary panic bars typically come with a dogging feature.  This allows for the device to be disengaged (unlatched) if desired.  This would allow for people on the exterior of the building to enter without a key or having someone from inside open the door manually.

Fire-rated exit devices, on the other hand, cannot be produced with a dogging feature.  Building and fire codes have specific regulations regarding the locking and unlocking of fire doors.  These are typically not installed on a building’s exterior, but rather inside, often to separate the main office of a business from its warehouse, or to separate one unit from another in a multi-unit commercial building.

By law, fire doors must remain locked at all times. This helps to prevent the spread of fire from one part of a commercial building to another (i.e. between units in a multi-unit building/complex.) This is why fire-rated mechanisms are not sold with a dogging feature.  This ensures that fire doors are not inadvertently left unlocked.

Electric latch retraction allows a door to operate with some extra features.  Doors outfitted with electric latch retraction can be remotely unlocked.  One example of this is a residential, multi-unit building where visitors must be “buzzed in” by someone who lives in the building.  This feature allows the building owner/occupants to control who enters.  Other features include remote dogging (except in the case of fire doors) and automatic door operator.  When power is cut to the system, the door latches automatically until power is restored.  Doors can still be opened manually even in a power outage.

The Von Duprin EL conversion kit allows a user to retrofit a number of Von Duprin’s manual exit devices and convert them to electric latch retraction.  The kit can be applied to the 33, 35, 98 and 99 series of Von Duprin panic devices.  The kit can even be applied to fire doors and will maintain its fire rating and UL listing.

The Von Duprin EL Conversion Kit