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  1. #1
    Join Date
    May 2009
    Location
    Waterloo Ontario
    Posts
    61
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    Luxaire LP9C080 back fire

    Hey guys,
    Working on a variable speed luxaire today. It's a 2011 80k horizontal propane conversion. The issue I'm having is the burners ignite prior to the end of the burners. Pop back I heard it was called, basically getting an uneven mixture inside the burner and causing swirling and lighting gas almost right out of the office. It varies and does it sometimes on some, sometimes on others

    Here is what I've checked...

    -Pulled burners- no spider webs.
    -Checked for proper orfices for propane
    -lit with intake off
    -gas pressure is bang on. It's modulating. But low fire is 1.8" high fire is 9.8" (calls for 1.6-10")
    -cleaned out each office with drill bit
    -burners are aligned as far as I can tell
    - did a combustion test as well

    Any help is appreciated. The only time I've seen this was a spider web. And it was consistently one burner. Not randomly on all 4 low-high fire.




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  2. #2
    Join Date
    Jul 2007
    Location
    Virginia
    Posts
    8,501
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    Quote Originally Posted by Purcell1 View Post
    Luxaire LP9C080 back fire

    It's a 2011 80k horizontal propane conversion.

    -burners are aligned as far as I can tell

    Any help is appreciated.
    Is this a recent propane conversion?

    Is the unit tilted back to front more than it’s 1/4” install manual restriction?

    Propane burners should be running slightly down hill, which would mean you would want the unit at least perfectly level, and preferably tilted front to back by 1/4”.
    Instead of learning the tricks of the trade, learn the trade.

  3. #3
    Join Date
    May 2009
    Location
    Waterloo Ontario
    Posts
    61
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    I'll give that a go- it's been heating fine- doesn't lock out or trip the roll outs. Was just doing an annual inspection...


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  4. #4
    Join Date
    May 2016
    Location
    Toronto, CAN
    Posts
    81
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    That furnace uses the pressure transducer to control inducer and gas valve. Should light off on high fire then drop down to satisfy discharge air sensor. Thinking either too much fuel or not enough draw. I believe it's all DC volts. Would suggest calling York tech support to get the numbers.

    Been a while since I worked on one, but when I did resi work I kept a transducer on my truck cause it could.throw the thing out of whack.

  5. #5
    Join Date
    Jan 2017
    Location
    Tyler, Texas
    Posts
    23
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    Have you verified that a proper draft is being pulled? I know the pressure switch is obviously closed but doesnt guarantee the draft.

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  6. #6
    Join Date
    Nov 2014
    Location
    Portland, Oregon, United States
    Posts
    150
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    Good luck with York tech support, I was on hold for about an hour.

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  7. Likes Mileo407 liked this post
  8. #7
    Join Date
    May 2016
    Location
    Toronto, CAN
    Posts
    81
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    There is Canadian tech support which isn't too bad usually just leave a message before I go and will get a call back.

    There is also a bias adjustment on the valve which generally don't get touched but but may be needed. I remember seeing that in the instructions on a new way valve.

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