Protected Premises Emergency Control Functions (Relays length limitations)

Fire alarm relays are used to accomplish a number of functions: anywhere from shutting down an air handling unit, releasing an electrically help door, activating an exhaust fan, or activating elevator recall function.  Because the requirements of monitoring of the fire alarm circuit conductors only applies to the conductors between the fire alarm control unit (ex, fire alarm control panel) and the fire alarm relay, NFPA 72 limits the amount of circuit conductors between the relay and the controlled device to 3 feet.  Below is an installation detailing the above described.  Fire alarm relays used for elevator recall are installed in the elevator machine room; within 3 feet of the elevator controller.

NFPA 72 – 21.2.4* A listed relay or other listed appliance connected to the fire alarm system used to initiate control of protected premises emergency control functions shall be located within 3 ft (1 m) of the controlled circuit or appliance.


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