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  1. #1
    Join Date
    Oct 2002
    Location
    Lexington, NC
    Posts
    5,144

    Kitchen Exhaust/fire control setup

    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.
    Thanks guys.
    The main thing is to keep the main thing the main thing!

    If "the grass is greener on the other side", it likely has been fertilized with Bull$hit!

  2. #2
    Join Date
    Jan 2008
    Location
    Lake Worth, FL
    Posts
    111
    sounds like a weird setup. usually 24 volts and 120/240 volts are separate. 24 volts would be the control circuit tied to the fire system. when the fire system is activated the exhaust fan stays on, the makeup air shuts down and power/gas should shut off on the cooks line. that's where the shunt trip comes into play for shutting down electric on the cooking equipment.

  3. #3
    Join Date
    Oct 2002
    Location
    Lexington, NC
    Posts
    5,144
    For that to happen they would have to run the 24v for the makeup contactor through the contactor on a n/c leg. The line voltage for the makeup, exhaust and control transformer were in the same panel.
    You say it shuts down the cooking equipment. Does it do this via a gas safety valve? If so, the pilot must come in before it like on a boiler, because the pilot lights never went out.
    The main thing is to keep the main thing the main thing!

    If "the grass is greener on the other side", it likely has been fertilized with Bull$hit!

  4. #4
    Join Date
    Jan 2008
    Location
    Lake Worth, FL
    Posts
    111
    Sounds like it's not up to code - at least in Michigan

  5. #5
    Join Date
    Oct 2002
    Location
    Lexington, NC
    Posts
    5,144
    That would be no suprise at all.
    So can you give me a general run down of how this system is supposed to work? I can see getting a phone call at a restaurant with an exhaust not running and stumbling on this again. Not that it wouldn't be obvious if everything is shut down, but if an exhaust fan isn't working and you see a contactor that isn't pulled in, well, most techs are going to waste time on checking it out when not needed. Thanks
    The main thing is to keep the main thing the main thing!

    If "the grass is greener on the other side", it likely has been fertilized with Bull$hit!

  6. #6
    Join Date
    Jul 2010
    Location
    So-Cal
    Posts
    580
    Probably a normally closed contactor. When I worked for a fastfood company as a tec. We had fire suppression system called "ansel" system.

    If someone pulled the ring to set off the ansel say for a grill fire then a micro switch in the ansel system would close and send power to that contactor and open it, killing power to a solenoid valve for the gas line to that piece of equipment. (And the hoods.)

    Not all stores had an electrical solenoid some were mechanical where when you pulled the ring the cable that was connected to it would close the gas off to that piece of equipment.

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