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    multiple furnaces going off on flu limet (3 Posts)

  • dandutcher87 dandutcher87 @ 9:40 PM
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    multiple furnaces going off on flu limet

    i have never seen anything like this before we have 3 furnaces about 100,000 btu non condensing induced draft all going off on high limit that is on draft motor outlet. I took flu pipe off and there is a strong draft from chimney i do not have proper tools to check but it appeared ok. I am getting 4.7 02 and about 160ppm co sometimes fluctuating a bit +-20 ppm. flu temp is about 400F. There appears to be plenty of make up air. all 3 furnaces are doing the same thing.

    other notes:
    filters clean
    ambient room temp 70
    gas pressure 3.5" manifold side
    natural gas
    3 furnaces in same room common venting
    This post was edited by an admin on February 25, 2014 9:51 PM.
  • unclejohn unclejohn @ 10:36 PM
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    Is this a home

    Or a business? Sounds like you have a sever negative pressure in the space.
  • drhvac drhvac @ 6:39 AM
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    air flow

    How about your temp rise? Is it right according to the nameplate?
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