This month’s reader questions focus on sprinkler alarms. As it turns out, there is a lot of confusion over which NFPA rule — 13 or 72 — applies.
Why does my local fire inspector think the fire alarm outdoor horn only activates upon water flow? We have installed a basic fire alarm system monitoring the sprinkler system, manual pull boxes, a few smoke detectors to protect the fire alarm control units, and horn/strobes throughout. The outdoor horn is part of the building’s NAC and will sound whenever an alarm signal is initiated from any device, not just water flowing from an open sprinkler head. The inspector quoted NFPA 13 which stated that the appliance must sound whenever, and as long as, water is flowing.
When researching rules, I always start with the state’s adopted Building and Fire Codes, since this is the written law enforced by our inspectors. The building and fire codes tell us what function, service, operation or feature is to be provided for specific structures. The referenced standards then tell us how to accomplish these requirements.
NFPA 13 covers the installation of fire sprinkler systems; NFPA 72 covers equipment related to fire alarm systems. At the beginning of the ICC building and fire code sprinkler requirements, it states “Where the provisions of this code require that a building or portion thereof be equipped throughout with an automatic sprinkler system in accordance with this section, sprinklers shall be installed throughout in accordance with NFPA 13…”
Later, when addressing notification appliances for sprinkler systems, the ICC codes require “an approved audible device, located on the exterior of the building in an approved location, [to] be connected to each automatic sprinkler system. Such sprinkler water-flow alarm devices shall be activated by water flow equivalent to the flow of a single sprinkler of the smallest orifice size installed in the system. Where a fire alarm system is installed, actuation of the automatic sprinkler system shall actuate the building fire alarm system.”
The ICC and NFPA 13 both require an audible appliance, but it is NFPA 13 that tells how to arrange the equipment to provide this outdoor audible signal. It is also NFPA 13 that is the source of the requirement that the audible signal must operate as long as water is flowing. NFPA 13 tells the sprinkler contractor that they may use a water motor gong or an electric sounder such as an outdoor-rated bell.
Water Motor Gongs: The water motor gong is a large, wall-mounted bell covered with a protective guard. It uses a clapper attached to a paddle wheel to make it ring. When a sprinkler head opens, water pushes the flapper valve out of the way which covers an “alarm port.” Piping feeds water from this port to the water motor gong. As long as the sprinkler system flows water, the water motor gong will operate, which is a requirement of NFPA 13.
Water flowing through the water motor gong is allowed to drain onto the ground. If the fire department arrives to find this gong ringing slowly, they can assume that a fire had caused several heads to open and a larger fire may be present. By attaching the pumper truck to the Siamese hose connections, the firefighters listen for a speeding up of the water motor gong, indicating their pumper truck was helping the situation with more water and pressure. Without the pumper truck, lots of open sprinkler heads will just dribble instead of providing an effective water spray.
Electrical Sounders: NFPA 13 also allows an electrical sounder to be used instead of a water motor gong. These 120vac appliances are wired to the normally open contacts of a water flow switch. As with a water motor gong, as long as water flows, the bell sounds.
Although this electric bell lacks the feedback provided by a water motor gong, it is allowed to satisfy the outdoor audible signal requirement of NFPA 13 and the ICC codes. NFPA 13 then states that this electric sounder is to be wired in accordance with the NEC, but allows and acknowledges that this electric sounder’s wiring would not be monitored for integrity. Birds’ nests and corrosion have always caused reliability problems for both the electrical- and water-powered outdoor sprinkler sounders.
The outdoor audible signal described above in NFPA 13 also meets the outdoor sounder rule for the ICC codes. It should be noted that the rule for having the outdoor sounder continue to operate as long as water is flowing, is strictly an NFPA 13 requirement. The last rules in the “Attachments - Electrically Operated” section of NFPA 13 says that if you install an electrically operated alarm appliance are part of a fire alarm system, then the alarm system is to comply with NFPA 72. The most applicable requirement provides that the wiring to our notification appliances be monitored for integrity, and not simply fed through a water flow switch as allowed by NFPA 13 when there is no fire alarm system provided.
Is there a requirement in NFPA 72 to install an outdoor audible appliance that is not able to be silenced and must sound as long as water is flowing? Must it sound only if water is flowing even if the building’s fire alarm system is sounding?
No, this is not requirement of NFPA 72 or the ICC codes. These features are solidly under the alarm attachment rules of NFPA 13; however, if you coordinate with the suppression contractor to provide the outdoor appliance feature for compliance with NFPA 13 (instead of the sprinkler contractor supplying a water motor gong or electric bell etc.), the AHJ may expect it to operate as they have known them to operate for about a hundred years now — sound only when, and as long as, water is flowing. This would require an intelligent control panel with a water flow zone/point capable of being mapped to a non-silenceable NAC.
How would the alarm company meet the ICC code rules for sprinkler monitoring?
You provide compliance with the monitoring rules that require code-mandated sprinkler systems to send signals off site. Since monitoring is not as expensive as it once was, the ICC code makes it so we no longer rely on the water motor gong signage prompting people to “Call fire department when sounding.”
Consider allowing the sprinkler contractor to provide compliance with NFPA 13 rules for an outdoor audible appliance. If you choose to supply an additional horn or horn-strobe, make sure to mark it “supplemental” on the submittal plans since you are not installing that sounder to provide compliance with NFPA 13.
Monitored systems have the ability to inform the local Fire Department dispatch personnel that the alarm was initiated by water flow, the smoke detector over the panel, or that one odd manual pull box required to be located somewhere in the building.
Greg Kessinger is SD&I’s fire alarm and codes expert and a regular contributor. Please email him your fire & life safety questions at [email protected].
