I worked on an exhaust/makeup air system yesterday, and I have a couple of questions as to how this device may be controled. Basically we had 24 volts on the switch at the hood. i had a magnetic style contactor that was hooked to a shunt trip breaker in the panel. This contactor was rigged to trip the breaker evidently in the event that the fire supression system was energized. I had what checked to be 24 volts and 110 volts present on the contactor, and nothing powering it.
I am wondering if someone can clear up how this is set up and if they normally take the control voltage off of the transformer that is in the control circuit of the makeup air and exhaust system.
The problem wound up being a triped overload, possibly from a severe storm we had the night before.