When a duct smoke detector or fire alarm control panel goes off, the air handler serving the affected area must shut down, smoke dampers in that system must close, and fire doors held open on magnetic holders must release. A fire alarm relay for HVAC shutdown carries out the first of these: the panel output drives the relay coil, and the relay contacts open the fan’s control circuit. The same interposing arrangement is used to remove power from damper actuators and door holders. Where the Authority Having Jurisdiction requires that relay to be listed for fire alarm use, it must carry a UL864 listing, which a general-purpose UL916 relay does not provide.
Functional Devices, Inc. manufactures RIB® (Relay-In-a-Box®) enclosed relays for building automation. The standard RIBU1C is listed to UL916 for energy management, and its UL864-listed counterpart is the RIBU1C-RD.
This guide covers where the shutdown requirement comes from, how a relay is wired between a panel and a load, the difference between UL864 and UL916, and which RIB® models carry the UL864 listing.
HVAC Shutdown Requirements Above 2,000 cfm
The International Mechanical Code (IMC) requires smoke detectors in return air systems with a design capacity greater than 2,000 cfm, installed in the return duct or plenum upstream of filters, exhaust air connections, and outdoor air connections (IMC 606.2.1). Where multiple air handlers share a common supply or return with a combined capacity over 2,000 cfm, the shared system is subject to the same requirement (IMC 606.2.2). On activation, the detectors must shut down the air distribution system (IMC 606.4).
NFPA 90A places detection on the supply side of systems over 2,000 cfm instead. Which standard governs your specific application may vary, but in either case, the required action is the same: the fan must stop when smoke is detected, so the air handler does not move smoke from the fire area into the rest of the building.
How a Fire Alarm Relay Interfaces With a Panel
Fire alarm panel relay outputs and addressable control modules have limited contact ratings, so line-voltage loads such as fan starters and 120 Vac actuators are commonly switched through an interposing relay rather than wired to the module directly. The panel output energizes the relay coil at the panel’s operating voltage, and the relay contacts switch the controlled circuit at its own voltage.
For fan shutdown, the relay contact is wired into the fan’s run circuit, or into the unit’s control circuit on packaged rooftop equipment, so that the alarm condition opens it. Whether the relay is continually energized during normal operation or energized only on alarm is a design decision.
UL864 vs. UL916: Which Listing a Fire Alarm Relay Needs
UL916 covers energy management equipment, which is the standard that most RIB® relays used in HVAC and building automation system (BAS) panels are listed to. UL864 covers control units and accessories for fire alarm systems. A UL916 listing establishes a relay’s suitability for building automation duty; it does not establish suitability for connection to a fire alarm system.
Many Authorities Having Jurisdiction require that devices connected to a fire alarm system be listed for fire alarm use, which, for an interposing relay, typically means UL864. However, because the requirement is set locally—for example, fire alarm devices sold in the state of California must be listed by the California State Fire Marshal (CSFM)—confirm the required listing against the project specification and the Authority Having Jurisdiction before ordering any relays.
Fire Alarm Relay Applications
HVAC Shutdown
The relay contact opens the supply fan’s run circuit, or the unit’s control circuit on packaged equipment, when the panel goes into alarm. On systems over 2,000 cfm this is a code-required function under IMC 606.4.
Smoke Dampers
Smoke damper actuators are commonly spring-return, closing when power is removed. The relay interrupts actuator power on alarm, and the damper closes on its spring. Dampers that are part of an engineered smoke control system are governed by that system’s design and listing, which is outside the scope of this guide.
Door Holders
Magnetic door holders keep fire and smoke doors open only while energized. The relay removes holder power on alarm, and the doors release. Because a loss of power also releases the doors, the arrangement fails to the closed position.
UL864-Listed RIB® Relays for Fire Alarm Interfaces
The following models are UL864 listed on their current Functional Devices datasheets. Each is housed in an enclosure UL Accepted for Use in Plenum and rated NEMA 1.
- For a single SPDT interface with a 10–30 Vac/dc or 120 Vac control signal, the RIBU1C-RD switches 10 A resistive at 277 Vac and is listed to UL864 and by the California State Fire Marshal.
- Where the control signal is 208–277 Vac, the RIBH1C-RD provides the same 10 A SPDT contact with a 10–30 Vac/dc or 208–277 Vac coil, with the same UL864 and CSFM listings.
- For a 24 Vac/dc or 120 Vac control signal, the RIB2401C-RD provides a 10 A SPDT contact and is listed to UL864 and CSFM.
- For a higher-current or two-circuit interface, the RIB24P provides a 20 A DPDT contact with a 24 Vac/dc coil and is listed to UL864. Its datasheet does not list CSFM.
Frequently Asked Questions About Fire Alarm Relays
Does a relay connected to a fire alarm panel need to be UL864 listed?
Many Authorities Having Jurisdiction and project specifications require it, but the requirement is set locally rather than uniformly. Be sure to confirm the requirement before ordering.
What is the difference between the RIBU1C and the RIBU1C-RD?
Their relay and contact ratings are the same: 10 A SPDT with a 10–30 Vac/dc or 120 Vac coil. The RIBU1C is listed to UL916 for energy management. The RIBU1C-RD has a red housing and is listed to UL864 and by the California State Fire Marshal for fire alarm use.
Which RIB® relays carry the California State Fire Marshal listing?
On current datasheets, the RIBU1C-RD, RIBH1C-RD, and RIB2401C-RD list both UL864 and CSFM. Confirm any listing requirements with your Authority Having Jurisdiction. Learn more about sourcing RIB® products in California.
Sourcing UL864-Listed Fire Alarm Relays
To source UL864-listed RIB® relays, find an authorized Functional Devices distributor near you. Fire alarm and security supply houses that want to stock the RIB® line can apply to become an authorized RIB® distributor.