Thanks to Joseph R. Cervantes, Sr. for creating this FAQ! You can connect with Joseph HERE
NFPA 72 requires that the maximum distance between the fire alarm relay and the emergency control function needed to be within 3 feet of one another. This has been misinterpreted by many contractors who install relays in elevator rooms, on rooftops and in small crammed damper plenums that are impossible to service later or easily access for installation.
If you apply the standards correctly, you will find that all of these relays can be mounted in one location with an unlimited distance between the device controlling the emergency control function and the function itself. In this example, the devices are within the 3 feet requirements per NFPA 72 21.2.4 and can be mounted where serviceable. Mind you, this only applies when an interposing control relay is used, which meets the intent of NFPA 72 21.2.10 and is listed for the loads that are being controlled.