Fire dampers on furnaces / and furnace shut downs

[ronball]

We are finishing up a 4 story fraternty. Inspectors now says that when the fire dampers shut down in the common halls, which we do have power to. That the furnaces also have to shut down. Is this a new one. And what method would be easiest to shut them down. They are all electric by the way. Naturally all walls and ceiling are drywalled.

 

[Buck Parrish]

I assume the furnaces are vented through the dampers. I f so the inspectors request sounds reasonable.
Shunt trip breakers or relays can make this happen.
You night want to check with the hvac guys.
The fire marshalls will eventually inspect the system again. I suppose you could ask them to visit now for thier view on the situation.

 

[luckylerado]

Fire dampers do not require power; they close when a small strip of metal holding them open melts and are only resettable by replacing this metal strip, I call it a fuse.

A smoke damper does requires power (usualy 120 v)to hold it open and should be controlled by a fire alarm system relay. I am assuming that smoke detectors in the area or in the duct work decide when the dampers close. These same detectors can be programed to control a secondary relay for the shutdown of the hvac equipment.

Shut tripping the unit is a bad idea and i do not recommend it. Sending 2 conductors to the low voltage side of the equipment from the secondary relay normally closed contacts is the appropriate way. Not knowing what type of equipment you are dealing with, I am not comfortable telling you which wires to grab in the low voltage wiring but basically you want to let the unit go through it's shutdown process as if you turned it off at a thermostat. The AHJ should accept some delay in the shutdown process but he is the boss i guess. 90 seconds is generally acceptable.

 

[ronball]

So then, I think I could install a nc relay on the thermostat control, then when dampers were activated , the thermostat would turn off , if it was running. does this sound resonable.