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    Gas furnace short cycling (4 Posts)

  • Mappleman Mappleman May 18, 2010 @ 9:03 PM
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    Gas furnace short cycling

    I'm an oil heat guy.. A buddy of mine has a gas fired hot air furnace that is short cycling. It will satisfy the t-stat eventually, but it only stays lit for about three minutes before it shuts the burner off, relights, runs three min., then shuts off again. I've not looked at it yet, I'm looking for some place to start, (besides the flame roll out switch)
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  • JStar JStar May 18, 2010 @ 9:12 PM
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    Checklist.

    High limit safety. Take a temperature difference. The supply shouldn't be hotter than the max rating for the safety. Should be specified on the nameplate. A high delta T is a cause for concern.

    Flame sensor may be dirty or faulty.

    Pressure switch could be opening during the cycle.

    Gas valve, safety, or control wire terminals could be rusted or pitted.
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  • Mappleman Mappleman May 18, 2010 @ 9:35 PM
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    Gas furnace short cycling

    Thanks for the start points, I'll be at it this weekend. (no free work during the week)
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  • Tim McElwain Tim McElwain May 19, 2010 @ 6:22 PM
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    Send me an E-mail and

    I will send you a step by step checkout. My e-mail is gastc@cox.net
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