HVAC Shutdown by Fire Alarm System
HVAC Shutdown by Fire Alarm System
(OP)
Does anyone know if the Uniform Codes (UBC, UFC, UMC, etc) or NFPA 72 requires shutdown of all HVAC systems bringing outside air into an area on activation of the alarm system, either by the sprinkler flow switch or an area smoke detector? We have a large open office area (cubicles) served by a dozen rooftop air conditioning units.
Our fire alarm contractor insists that the code requires shutdown of all the HVAC units on activation of the building fire alarm.
Comments please. Thanks
Our fire alarm contractor insists that the code requires shutdown of all the HVAC units on activation of the building fire alarm.
Comments please. Thanks





RE: HVAC Shutdown by Fire Alarm System
PHarmer:
The contractor is confused. If your design is based on the Uniform Mechanical Code, shutdown of the respective air handler is only required if the unit has a discharge rate of 2000 CFM or greater.
NFPA 72 (2002 ed) allows the use of area smoke detection. However, its less expensive to use duct smoke detectors. These devices are listed for installation in the supply side of the air handler unit. If you already have area smoke detection, you may use it to shutdown the air handlers provided that detectors are provided throughout. This can create significant maintenance costs.
If one uses a duct smoke detector, it only needs to shutdown the air handler unit it is connected to.
Also, NFPA 72 only requires that the activation of the duct smoke detector to transmit a supervisory signal - it does not need to activate audible or visual alarm notification devices.
On a separate note, your post indicates that you have an office building that is sprinklered. If your applicable code is the Uniform Fire Code I am not aware of a fire alarm system requirement for a B occupancy unless its a highrise. Even then, smoke detection is not required in offices unless one is seeking increased exit travel distance.
RE: HVAC Shutdown by Fire Alarm System
In the case of air systems where "all portions of the building served by the air distribution system are protected by area smoke detectors connected to a fire alarm system" you don't need duct-mounted ones, but "upon activation, the smoke detectors shall shut down the air distribution system". There are other exceptions and limitations within the code(s) depending on the size of the fans (2,000 CFM), whether there is a "smoke control system", etc.
In general, however, the concept is to keep that "outside air" from feeding a fire. It depends, but I believe you'll find the Contractor is correct in this case.
Good luck
RE: HVAC Shutdown by Fire Alarm System
RE: HVAC Shutdown by Fire Alarm System
Is the detector on the supply fan inlet or supply ducting? Is the detector in the room?
Is there free ventilation between rooms or open areas?
Are the rooms sealed with fire doors?
Is this an office building, a hospital or an ocean going vessel?
Generally, if the detection initiates a suppression system such as FM-200, CO2 etc. then shutdown the fans and dampers to contain the suppression agent. I think that this is covered within old NFPA standards for computer rooms. You might not expect the old mainframe based standards to apply to a server room. Also, expect standards for a computer room to differ from standards for a hospital or a night club. ...
John
RE: HVAC Shutdown by Fire Alarm System