Many of you on this forum have firefighting experience. On rooftop air handlers with direct exhaust who decides what the unit does when the fire alarm goes off? Is it specific to the city or building?
Is it best to have the air handler exhaust smoke until the fire department cuts power? Would it depend on the estimated time to evacuate the building? Say run the exhaust for 45 minutes if it takes 30 minutes to evacuate the building? These are the same questions I am asking our customer but I would like to see the different applications and their effects that people have seen in real world applications.
I also know there are so many variables involved that it becomes complicated. From my Navy firefighting days I remember ventilating the compartment with a hatch, then someone opens a hatch on the other side and it creates a blow torch effect.
I would appreciate hearing your views on this application.
If it is only exhaust, then it would depend on whether smoke control is required by the mechanical code. If smoke control is not required, then there is no requirement to shut down an exhaust only fan .
Re: Air Handler Exhaust during fires.#6587505/15/0604:31 PM
I asked the same question because we have two offices. One the HVAC shuts down on fire alarm the other it does not. One building has two floors the other is single floor. I was told HVAC only needs to shut down on two story or up buildings. This is in Ontario Canada.
Re: Air Handler Exhaust during fires.#6587805/15/0609:48 PM
NJ_Grad, I believe that New Jersey statewide goes by the 2003 International Mechanical Code. Smoke control systems are handled by Section 513, which is a special animal regarding when it goes on or off. Section 606 is where duct detectors are required, which identify return or common supply and return locations requiring shutdown. There is no mention of exhaust.
Re: Air Handler Exhaust during fires.#6587905/15/0611:25 PM
This is an HVAC air handler with a split condensing unit. The fire alarm turns of the heater and/or the supply air blower. There are two exhaust fans blowing out horizontally on the left and right sides of the return air stack.
The whole unit can be disabled by a remote signal and of course disconnecting main power. It is currently set up to stop the supply blower and vent smoke with the exhaust fans until the unit is disabled. The customer has not responded yet on what they require and if their fire system can disable the unit if the fire is directly in the zone the air handler supplies.