TGPs HVAC experts

Discussion in 'The Pub' started by Slaphappy, Feb 17, 2015.

  1. Slaphappy

    Slaphappy Member

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    Calling TGPs HVAC experts

    I have a Ducane gas furnace model number 92G1UH070BP12. It's been off for a few days I was gone and came home to a house with temps at 34, frozen water lines in the crawl also.

    The unit calls for heat but when starting up it will try to ignite the burners but fails.

    I thought it may have been a frozen condensate line so I disconnected the line but it's will not light off.

    I'm getting an 3 flashes error on the control board = (pressure switch open with inducer on)

    I waited for the burner and fan to come on and tried to jump the pressure switch out but it's still not igniting.

    I have fuel, stove works and clothes dryer too.

    Any HVAC experts know what to try next?

    Glow switch gone bad maybe?

    Thanks!
     
  2. hellbender

    hellbender Member

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    Are other gas appliances working? Do you have gas pressure?

    I found the model on the Ducane website but can't find a schematic yet. Found it.

    I see a 24V circuit with a 3A fuse that feeds both flame rollout switches in series, leaves the furnace on red and loops thru the wall thermostat and returns on white, loops thru S10 and S18, then thru contact K1 thru S145 which pulls in the gas valve. If you have the schematic, you can follow that path with a VOM and see where the 24 VAC stops.

    Heres a link to the schematic.

    http://www.ducanehvac.com/_/pdfs/installation/Ducane_92G1_95G1_Downflow_Install.pdf
     
    Last edited: Feb 17, 2015
  3. Slaphappy

    Slaphappy Member

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    Thanks...........I'll see what I can find out.
     
  4. Slaphappy

    Slaphappy Member

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    I had reset the rollout switch.
     
  5. RCM78

    RCM78 Member

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    A rollout switch was tripped?
     
  6. Slaphappy

    Slaphappy Member

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    Yes it was.
     
  7. ACfixer

    ACfixer Member

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    Why?

    There are reasons rollout switches trip and I know that's exactly what Ralph (RCM78) is thinking. You don't just reset them and go about your business, they have manual reset limit switches vs. auto reset switches there because it means someone needs to put their eyeprints on it.
     
  8. LHanson

    LHanson Member

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    TGP awesomeness.
     
  9. RCM78

    RCM78 Member

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    If the PDF posted above is for your furnace it looks to have a clamshell style heat exchanger. They have two stamped out sheets of metal joined together by rivets to produce one section of the heat exchanger.

    Typical issues with clamshell's are the rivets pop out and that causes heat to blow out into the burner area (Exactly where the roll out switches are located).

    A tripped roll out is usually a very good indication of a breached heat exchanger...

    If it trips again have it checked out by a pro.
     
  10. Slaphappy

    Slaphappy Member

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    I understand and thanks for the information and the note of a safety concern.

    Our area had high winds outside which possibly didn't allow air to escape or other issues causing the switch to trip.

    After the reset the furnace cycled on and off and is functioning properly.
     
  11. RCM78

    RCM78 Member

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    If the furnace is vented properly into a termination kit, wind wont affect the venting. If it just has an exhaust pipe sticking through a wall or roof and the wind got in there it would open the pressure switch, not the roll out...
     
  12. ACfixer

    ACfixer Member

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    Listen to this man. It would take one heck of a wind to overcome the inducer motor's draft and trip a rollout. Like he said, the pressure switch is the safeguard against that.

    You mentioned freezing conditions, I would want to know that both the venting and condensate lines were installed as per manufacture's specs. And no water froze in the primary or secondary heat exchanger. If the furnace is installed in an upflow orientation then that's probably unlikely but I can't tell you how many times I've seen high efficiency (condensing) furnace installed incorrectly in the local mountains in the horizontal position and have it crack the heat exchanger or the collector box. The good thing is that if this is the case it will most likely trip again and at that time you really do need to call someone.

    I just caught that... Are you sure the rollout was tripped? Did you unplug the furnace at any time and perhaps allow it to reset and think you just reset the rollout switch? The main gas valve should never come on if the pressure switch doesn't make and should shut off immediately if it breaks at any time during the heating cycle. The error code pointing toward a draft failure of some sort + a tripped switch seems odd.
     
  13. Slaphappy

    Slaphappy Member

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    Thanks guys!

    The rollout was tripped as the unit started as soon as it was reset. I did turn the disconnect off to allow the unit to reset a few times when I was working on the unit.

    The unit has been running now for 18 hours cycling on and off after reaching temp set point.

    Clearly you guys are professional HVAC experts and the help and cautions are very helpful.
     

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