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  1. #1
    Join Date
    Jan 2020
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    Ever had this happen with a furnace? ...and what to expect out of a HVAC pro?

    Furnace is a 15 year old Ducane 92% 75000. Started acting strange the other night.

    1. Thermostat would call for heat
    2. Furnace would respond by starting ignition sequence
    3. As soon as the gas valve open, it would immediately close back up. And I mean immediately, like in milliseconds, not 1-2 seconds. One tiny puff of flame and then out.
    4. The thermostat would continue to call for heat, until eventually after 20-30 tries the valve would finally remain open and work as normal until the next call for heat, then rinse/repeat the issue.

    My first thought was that the control board was faulty - either the gas valve relay, or the drive circuit for said relay. But I eventually fixed the issue by swapping out the thermostat. I suspect that the heater thermostat relay was somehow affecting the gas valve relay in some sort of feedback loop. Like maybe the closing of the gas valve relay would affect the thermostat relay which would in turn affect the gas valve relay drive circuit... I don't know, but swapped out the thermostat and everything is working fine now.

    Anyone ever run into an issue like this before?

    The second part of my question is a bit of a rant, but I would like to know what to expect out of a Pro. Before I did anything myself, I called a pro - a 30 year old established company, good reviews, recommended by neighbors, etc... The outside temps were supposed to get down to -10 F the next day (I'm in Minnesota) and I figured my odds of getting the furnace fixed quickly would be better with a pro.
    Tech comes out and is flustered after the first 30 minutes. I can hear him downstairs cussing saying things to himself like "what is going on?". Called the boss several times to run ideas. Eventually he decided that the gas valve must be faulty and needs to be replaced. Ran out, got the part, swapped it out - no change. Another hour or so of cussing to himself, I finally go down and offer "Could it be the electronics? maybe the control board or the thermostat?" He says, "No, No it's definitely not that - I think you have a gas pressure problem and it probably your regulator outside." (huh???? im thinking since he had previously told me gas pressure was low but within spec). At this point the owner of the company shows up, pokes around in the furnace for a few minutes, and
    gives me the news that sorry, there is nothing they can do, agrees with the tech that it's probably low gas pressure and the regulator outside - tell me to call the gas company. They say sorry, and pack up and leave.

    To top it all off, now it's 5 PM, the temp outside is dropping, the furnace won't turn on at all now, even after 30 or more tries - AND they left a tiny gas leak from one of the joints that he unscrewed to replace the valve.

    Luckily I was able to figure out and fix the issue myself. Besides the obvious, that I am never calling this particular company again -does this sound like gross incompetence, or is it possible the owner of this company just decided he had
    invested enough time in this issue and it was time to cut bait. I think it's the former and my wife thinks its the latter.

    Is it possible that this is just a really weird problem that normally isn't seen? Are HVAC pros typically trained to debug electronics like control circuits and thermostat issues? I would think that it's part and parcel with the job, no?

  2. #2
    Join Date
    Aug 2001
    Location
    Pavilion, NY
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    3,492
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    Sometimes the simple ones are the hardest.


    Sent from my iPhone using Tapatalk
    ...

  3. #3
    Join Date
    Oct 2016
    Location
    Clearwater, Florida
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    Yes, it's part and parcel of the job, it's THE job, figuring out what's wrong is what we do.

    I didn't read the entire post but it sounds like either a control board or a flame rod problem.

  4. #4
    Join Date
    Nov 2006
    Location
    Athens, Ohio
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    7,313
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    Was your old thermostat a Nest? They are notorious for intermittent problems.
    AOP Rules: Rules For Equipment Owners.

    Free online load calculator: http://www.loadcalc.net/


    There = not here. Their = possessive pronoun. They're = they are
    It's = contraction of it is. Its = the possessive form of it
    Too = also. To = expressing motion. Two = 2
    Then = after that, next. Than = indicates a comparison.
    Questions should end with a question mark "?" Statements end with a period "."

  5. #5
    Join Date
    Jul 2010
    Location
    nebraska
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    2,810
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    We go in blocks and narrow it down to point of failure, following the sequence of operation with our meters. If a thermostat never dropped the 24v call for heat then we would move on to the board ,safeties and continue through the sequence components.

  6. #6
    Join Date
    Oct 2006
    Location
    The Beach
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    1,020
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    I have stopped useing the Nests.
    Blue Fox

  7. #7
    Join Date
    Jan 2020
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    Thread Starter
    OK, so it definitely sounds like in the future I should expect a tech to be able to electronics troubleshooting. I'm batting 0 for 3 for HVAC companies since moving to this state. Will have to keep trying different companies till I find a good one.

    The t-stat wasn't a Nest, it was an older White and rodgers. Good to know they might be problematic. I have a friend who installed one a year ago and he loves the thing. Was thinking of getting one myself after hearing his glowing reviews.

  8. #8
    Join Date
    Dec 2002
    Location
    SouthEast NC ICW & Piedmont Foothills
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    7,927
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    When the need arises for a service call again; when you place that call, ask the perspective organization if their technicians have adequate test instruments. Unless a LOT was left out of your details; there was a lot of guessing and very little troubleshooting.
    It`s better to be silent and thought the fool; than speak and remove all doubt.

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