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  1. #1
    Join Date
    Sep 2006
    Location
    Anchorage Alaska
    Posts
    562
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    Direct Fired Gas Make Up Air Unit Flame Failure

    This might seem like an odd problem!!! We have an older Direct Gas Fired make-Up Air Unit that flame fails at start up. Once the unit has been started and all it's fine for the whole day. So far new burner controller, new photo eye, and new ground. ????
    Law Of The Thermostat: He who has the thermostat wins!!!!!

  2. #2
    Join Date
    Jul 2012
    Location
    WA
    Posts
    2,905
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    Burner clean? Igniter positioned properly and clean? Proper pilot pressure?

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  4. #3
    Join Date
    Feb 2009
    Location
    Thonotosassa, FL
    Posts
    691
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    what brand is it? If its older I would make sure all the holes in the cast iron burner is clean out. there is also holes in back side of burner that get rusted so make sure they are clean. also the plate that make the V on the side of burner has a gasket that seal to burner make sure that is sealed well.

  5. #4
    Join Date
    Mar 2015
    Location
    Medford, N.Y.
    Posts
    6,225
    Post Likes
    Too much air flow cfm/velocity?

  6. #5
    Join Date
    Jun 2009
    Location
    Dallas/Fort Worth
    Posts
    3
    Post Likes
    Flame sensor?

  7. #6
    Join Date
    Jul 2019
    Location
    Twin Cites MN
    Posts
    45
    Post Likes
    I work with a lot of old MUA's. A lot of them needed grounds ran right to the pilot assembly to the burner control. I think the older rusted burners weren't making a good path.

  8. #7
    Join Date
    Jul 2018
    Location
    Wisconsin
    Posts
    1,103
    Post Likes
    There are small orifices in back of the burner that allow air to be pulled in. These need to be cleaned regularly or the flame starts to lift off the burner. Sometimes they are 100% blocked and rusted over and are hard to find.

    Sent from my SM-G960U using Tapatalk

  9. #8
    Join Date
    Jul 2018
    Location
    Wisconsin
    Posts
    1,103
    Post Likes
    .

    Sent from my SM-G960U using Tapatalk

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