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  1. #1

    Hood Exhaust Fan

    thanks in advance,
    i wired up a ansel system for a restauraunt, my question is, when say a fire starts in the kitchen, power to everything is cut off? i also have heard that the exhaust fan needs to stay running when a fire happens...wouldnt the exhaust fan suck up my agents extinguishing the fire? just curious in other cities if the exhaust fan needs to stay running or if it needs to be cut off from power as well.

  2. #2
    Join Date
    Apr 2002
    Posts
    11,808
    When the ansul goes off you kill the fuel/heat source under the hood with a mechanical or electrical valve for the gas, contactors for the electric heaters maybe.

    The NFPA code also says you have to kill all the power to items under the hood when the "WET AGENT" discharges, so even if there was just a little power on a gas appliance lighting up an LED or running a timer you still have to cut the power. You must also shut off the make up air, I cannot remember if that is in NFPA 17 or 96 but I assume it is so stop fanning the flames with combustion air.

    Sometimes you get a separate subpanel powering just the items under the hood plus the make up air fan and you pop the shunt trip breaker that feeds that panel with the firealarm or maybe even using contacts in the ansul panel, I have only done it with fire alarms. Probably could kill the make up fan through the ansul panel also. Sometimes devices are individually shunt tripped.

    You most likely want the exhaust fan going to get the smoke out of there.
    Last edited by Carnak; 03-13-2008 at 06:09 PM.

  3. #3
    Join Date
    May 2000
    Location
    Monmouth Junction-NJ-USA
    Posts
    6,001
    We install 20-25 exhaust hoods a year. Largest 30 feet, smallest 5 feet. When supression system is activated MUA fan and gas valve shuts down and ex fan stays on to remove smoke from area.

    New IMC code 507.2.1.1 requires a probe in the ex duct to activate ex fan when heat is present in ex duct. To many cooks do not turn on the fan and system activates.
    Last edited by rayr; 03-15-2008 at 05:30 PM.
    If you really know how it works, you have an execellent chance of fixin' er up!

    Tomorrow is promised to no one...

  4. #4
    Join Date
    May 2000
    Location
    Monmouth Junction-NJ-USA
    Posts
    6,001
    k
    If you really know how it works, you have an execellent chance of fixin' er up!

    Tomorrow is promised to no one...

  5. #5
    Join Date
    Feb 2008
    Location
    Michigan, Roseville
    Posts
    6
    I second RAYR

    Fan on please and let's hope the hood cleaning company did their job correct

  6. #6
    Join Date
    Sep 2007
    Location
    Just North of Dallas, Texas
    Posts
    97
    I had an Ansel system in my restaurant. I was told the unit was under pressure. So when the fusible link was severed/melted the discharge of the fire system forcibly put the fire out. Also, put the kitchen out of commission for a least a week. So we had portable fire extinguishers for the small stuff and let the Ansel take care of the big ones. I told the guys not to be heroes. I believe the system shut down my exhaust hood in case of fire.

    We had a small grill fire that I put out with a box of Baking Soda .....

  7. #7
    Join Date
    Jun 2004
    Location
    St Paul, minnesota
    Posts
    1,163
    Quote Originally Posted by rayr View Post
    We install 20-25 exhaust hoods a year. Largest 30 feet, smallest 5 feet. When supression system is activated MUA fan and gas valve shuts down and ex fan stays on to remove smoke from area.

    New IMC code 507.2.1.1 requires a probe in the ex duct to activate ex fan when heat is present in ex duct. To many cooks do not turn on the fan and system activates.
    alot of states (including mine) have omitted 507.2.1.1

  8. #8

    507.2.1.1

    The code actually states that the exhaust equipment must turn on whenever the equipment is in operation. So when you turn on only one burner on a twelve burner stove the exhaust system must automatically turn on. There is other equipment available other than an EMS to accomplish this.

  9. #9
    Join Date
    May 2000
    Location
    Monmouth Junction-NJ-USA
    Posts
    6,001
    The criteria here is that the fans must turn on within 3 minutes with 2 burners operating and filters in place. Just had a test last week. Check my post is WOP and you will see the interlock panel we use. It also has an off delay that allows the fans to operate up to 10 min after shut down to dissapate the residual heat.
    If you really know how it works, you have an execellent chance of fixin' er up!

    Tomorrow is promised to no one...

  10. #10
    Join Date
    Oct 2007
    Location
    Plainfield Il
    Posts
    43
    Once the system is triggered the shunt will take out all equipment and the is a gas shut off for all gas equiptment. The exhaust fans should stay running to clear the smoke.

  11. #11
    Join Date
    Mar 2009
    Location
    State College, PA
    Posts
    17
    The fan also is on to ensure fire suppressant is pulled thru the exhaust duct to extinguish duct fire.

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