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  1. #1
    Join Date
    Feb 2012
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    Sodak!
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    5

    Duct Smoke Detectors

    Hello:
    I mainly deal with commercial refrigeration, but was called out for a fire alarm caused by an HVAC smoke detector. When I arrived the audible alarm had obviously gone off because the fire dept. Was on-site. I found that only one of five AH's smoke detector had tripped on the boiler sys. I removed the clear plastic cover and checked the filters, screen, and tubes; all were clean. The detectors are located in the supply air plenum three feet from each AH. After speaking with the customer I found out that this wasn't the first time that that exact unit had tripped. Any ideas on what else to troubleshoot would be greatly appreciated.

    Thanks

  2. #2
    Join Date
    Jul 2011
    Location
    East coast USA
    Posts
    973
    did the AH unit go off as well? just wondering

    the smoke heads are in the supply air plenum, not the return?

    either the smoke head is getting old, or dust from the return kick up and make it go off. if its bringing in outside air, i had trucks parked close and their exhaust gets pulled in. belts could be slipping and burning, sometimes water mist can set them off. depending on the age i would replace if everything else i said does not apply.

  3. #3
    John Culpepper's Avatar
    John Culpepper is offline CHANGE YOUR EMAIL ADDRESS Professional Member*
    Join Date
    Oct 2007
    Location
    Austin Texas
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    1,778
    Mine will go off when the heat strips are activated.
    Nemo me impune lacessit.

    How much blood do I have to bathe in to get clean?

    Don't look down on anyone unless you're helping them up.

  4. #4
    Join Date
    Feb 2012
    Location
    Sodak!
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    5

    smoke detector dilemma

    Hello:
    My next question, assuming the detector assy needs to be replaced, is where can I find the manufacturer or model. The only numbers I see are on the control board, but the board manuf. is not listed either! Is there a monopoly on smoke detectors or are manuf. Avoiding liability.
    Thanks

  5. #5
    Join Date
    Jul 2011
    Location
    East coast USA
    Posts
    973
    Quote Originally Posted by refrigeratrix View Post
    Hello:
    My next question, assuming the detector assy needs to be replaced, is where can I find the manufacturer or model. The only numbers I see are on the control board, but the board manuf. is not listed either! Is there a monopoly on smoke detectors or are manuf. Avoiding liability.
    Thanks
    I would talk to your fire system vendor. Duct smoke detectors are pretty standard but you want to make sure its compatible with the fire system your have.

  6. #6
    Join Date
    Jun 2009
    Location
    ontario cali
    Posts
    10

    smokes

    i havae found if the hole in the tube are dirty they cause it to go off also. try to check http://www.systemsensor.com/products/hvac-conventional they are who we use alot that has ther info on it to.

  7. #7
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    18,593
    Two major failure modes are a loose terminal screw, or a defective supervisory relay. Look harder, you will find the info. Most likely a System Sensor unit.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

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  8. #8
    Join Date
    Jan 2012
    Posts
    42
    Quote Originally Posted by John Culpepper View Post
    Mine will go off when the heat strips are activated.
    Most definitely. Ran across this a few times, recently. Also, check for short.

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