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There'S still a lot of confusion regarding the use of certain relays and their installation locations when they are used to perform fire safety functions. NFPA 72 states "Fire safety functions shall be permitted to be performed automatically" and electrical relays are the primary means used to perform these functions automatically. Section 4.4.7 requires the wiring between the FACP/FACU (fire alarm control panel/or unit) and relay be "monitored for integrity" where opens/grounds will cause a trouble signal. There's a second option which allows "a single open or a single ground-fault condition in the installation conductors" between the FACP and your remote relay to cause the activation of the fire-safety function. When applying this second option your wiring "is considered self-monitoring for integrity."
The starting point for the rules specifying the use and location of these relays are found in NFPA 72 (2007) at section 6.16. Here you will find that relays must be "listed for the purpose." Again, there are two choices; the addressable relay, or a relay UL-listed for fire alarm use that's electrically compatible ("within the voltage and current limitations") of the FACP. Addressable relays are sometimes the easier option to choose since the address of the relay is "monitored for integrity in accordance with 4.4.7" and the relay connection may be a nearby signaling line circuit (SLC) as opposed to home run wiring it to the FACP.
Section 6.16.2.2 allows you to choose between two locations within 1 m (3 ft) of "the controlled circuit or appliance." First, let's consider "the controlled circuit" option. Bringing 24-volt DC door holder wiring to the FACP may be easier than bringing its AC power supply to the FACP or installing another relay. In the door holder application you will have installed your relay within 3 feet of the controlled circuit. The distance from the controlled appliance to the FACP or the distance from the "controlled appliance" to the devices it controls isn't regulated by code.
Let's say you wish to kill the power to an electrical sub-panel containing breakers for the AC outlets on a nightclub's stage, its fog machine, sound system and/or laser/disco lights. This option assures the alarm signals will not be lost in all the club's music and lights. While this is not a specific code requirement, the owner may prefer this over adding lots more audible/visible notification appliances. When you are controlling AC circuits of 120 volts or higher, you may not want to pipe that heavy gauge cable over to your FACP's on-board relay. Instead, run your fire alarm wiring to where these outlets get their power and use a relay capable of handling the switched load of the contactor. (Note: If your remote relay isn't rated for operating the contactor, the electrical contractor may need to install an additional relay after your fire alarm relay that does have contacts suitable for operating the contactor. Only the wiring between the FACP and remote relay is required to be either fail-safe or monitored for integrity.)
The example shown in Fig. 4 indicates the spacing permitted by 6.16 and their relationship is explained in the annex of NFPA 101, the Life Safety Code:
"A.9.6.5.4 Control devices (fire alarm relays) can be located at a motor control center that is located floors away from the device to be activated, such as air-handling units and exhaust fans located on the roof. The requirement for monitoring for integrity only applies to the installation wiring between the fire alarm control unit and the auxiliary fire alarm relay. It does not apply to the wiring between the auxiliary fire alarm relay and the emergency control device (for example, motor stop/start control relay) or between the emergency control device and the equipment to be controlled (for example, air-handling units and exhaust fans). For example, although the auxiliary fire alarm relay is required be located within 3 ft (0.9 m) of the emergency control device, there is no limit specified for the distance between the emergency control device and the equipment to be controlled."
Since a relay used for elevator shunt trip must be located within three feet of the device it controls, it is located within three feet of the shunt trip disconnect, not the elevator motors. Section 6.16.4.4 requires the FACP to monitor the voltage needed to perform the trip, which is usually 120 VAC. To comply, use the terminals provided by the shunt trip disconnect wired and make sure it is programmed/defined as a supervisory signal. Some elevator shunt trip manufacturers may provide a microswitch on the power disconnect handle that bypasses (shunts) these terminals so when the power to the elevators is shut off for maintenance, a supervisory alarm isn't caused unnecessarily. The wiring to the relay is fail-safe (your original option #2), but there is no FACP feed-back in this event. An "optional IDC zone" may be used to supervise the relay and annunciate that power to the relay has failed, causing an elevator shunt-trip. See Fig. 5. When smoke detectors use a relay base for elevator recall, it's using the "controlled circuit" option.
The FACP may perform other safety-related functions besides those mandated by the building and fire codes. (See 6.16.2.1.) The fire alarm system can be used to control other devices to add to the general safety by allowing easy fire fighter access to the property and activate additional lighting to illuminate the area of the fire department's hose connections at the rear of the building. If faults in the wiring between "supplementary system components" doesn't "affect the required operation of the fire alarm system," then the wiring doesn't have to be monitored for integrity. See Fig. 6 and section 4.4.7.1.4.
When relays are used to interconnect other control units located within 20 feet of each other, the wiring is not required to be monitored for integrity. See Fig. 7 and section 4.4.7.1.8.
Additional facts:
- Two-wire smoke detectors (with integral relays) used for elevator control must be capable of operation even when the other devices (including heat detectors and pull boxes) on that circuit are in alarm. See 6.16.2.4.
- The building owner must demonstrate the proper operation of all fire safety functions by an operational test at the time of system acceptance. Even when fire safety functions are not required by code, they should always be an option offered for your customer's consideration.
Greg Kessinger, SET, CFPS, teaches NICET training classes to fire alarm system designers and installers. You can reach him at Greg@firealarm.org.
author: By Greg Kessinger SET, CFPS