ECN Forum Forums General Topics of the Trade General Discussion Area Air Handler Exhaust during fires.

Thanks, Don: I stand corrected.

My experience of hoods and the like is that if the flames are vented straight up, it will close an in-tumescent barrier, by virtue of a temperature rated fusible wire link.
These are also used at corners of ducting.

There was a mistake in the write up and the controls are by a third party.

They said that their building code requires venting smoke with the exhaust fans with fusible links in the return air fire dampers so that if it gets too hot it shuts the damper and a differential pressure switch cuts out the exhaust fans after that.

Fire suppression systems used in commercial kitchen hoods are UL listed to operate w/the exhaust fans on or off. Leaving the exhaust fan on helps to distribute the suppression chemical throught the hood and duct. This also helps to move the combustion gases out of the fire area, improving visiblity for the responding fire department. The intake or make-up air is to shut down.

There is an IBC requirement to shut down air handling ducts moving 2000 CFM or more. This requirement may be modified by the type of occupancy, building construction and the whim of the building inspector.

Fireguy

Fireguy is correctm as far as the way we do it here. Every fire-suppression system we've wired in has the same parameters:

The exhaust must run, regardless of the switch's position, and the intake must not run, regardless of the switch position.

I figured out a way to do it using ony one of the two microswitches ours come with, requiring only three conductors between boxes.

Larry, could I trouble you for a diagram of your wiring? Most electricians have trouble leaving the exhaust on and shutting down the intake. I am often asked how to wire the contactors and I know just enough about wiring to hurt myself. Hey, are those wires supposed to spark like that?
Thank you in advance.
fireman@eoni.com