Furnace starts blowing cold air in the night?

Discussion in 'Heating / Cooling Systems' started by insaniak, Apr 2, 2016.

  1. insaniak

    insaniak New Member

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    Factory installed furnace doesn't seem to run all night. It will run hot for a while and then we wake up at night and it is just blowing cold air. It started blowing cold air sometime around 2am because that is when I woke up to turn it off because it seemed to be making us colder because of it.

    Would this happen if we run out of propane?

    Later that day we ran out of propane while cooking breakfast (I was expecting to run out since it was low anyway when the trip started)

    This is my first popup and I'm very DIY.
     
  2. gardenbliss

    gardenbliss Well-Known Member

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    My guess would be yes, if you are low on propane but the battery is still charged, the blower will still blow air but no heat from lack of fuel.
     
  3. terry1419

    terry1419 Active Member

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    My first reaction is yes, you ran out of propane. There could be other reasons but the fact that you knew the tank was low at the start and then later ran out while fixing breakfast almost makes it a no-brainer. Myself and many others use a small portable space heater if using an electric site to save on propane.
     
  4. ChocoChock01

    ChocoChock01 On the road aagaain See Rallies below;

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    Since you were low, as it proceeded towards sunrise, it also got colder (without other circumstances such as a thermal blast off the desert). The pressure decreased in the tank and no propane flowed to the heater (that still had battery power). In the morning, it warmed up a little and the remaining gas was pressurized for the stove.


    That's only a guess. [:D]
     
  5. insaniak

    insaniak New Member

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    Thanks for the responses. Just wanted to confirm my suspicions since I don't know exactly how it would run. I'll be replacing my propane tank before I go again.
     
  6. ChocoChock01

    ChocoChock01 On the road aagaain See Rallies below;

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    What i do, is carry a second or third tank and switch them out depending on how much is in each.


    Such as, if I know the PUP tank is low for the evening I would put a "fuller" tank on and use the lower filled tank for breakfast or the firepit.


    Easy fix and a relatively inexpensive cure for making the trip comfortable.
     
  7. Colemancamper24

    Colemancamper24 New Member

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    This happened to me once. It ended up being the battery charge was enough for the blower to run but not keep the furnace burning. I believe there is a safety device that shuts off gas flow when your battery runs below around 80% time to upgrade to a better battery/batteries.
     
  8. Antipodes

    Antipodes Call me Paul

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    If you completely ran out of propane, the system will recognise no flame and shut the heater down with a 2 minute cooling cycle.
    If there is enough to just keep the flame going, but effectively insufficient heat being produced to warm the cabin, then it will just run continuously as you describe.
    Almost all of the suggestions here point to the low propane as the obvious issue. As ChockaChock says, carry an extra bottle so that you can switch when or before it gets low.
    Please do comment back if you found it is still doing it with a full bottle.

    I don't believe the furnace has a voltage cutoff (Not that I have seen in any of pop up models anyway, but could be wrong) as such to operate as a battery safety device. Some specs do state that the battery voltage should be 10.5 volts minimum and 13.5 volts maximum. (However depends on which furnace as to the exact specs)
    If the battery voltage dropped off very low then more than likely the fan will turn slower and not put sufficient air through to operate the sail switch. This will cause the furnace to go into shut down with a cool down period, but it will not restart. (need to reset the thermostat to off and on again to reset the furnace logic control.)
     
  9. insaniak

    insaniak New Member

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    My battery was replaced a week before our trip.
     
  10. ChocoChock01

    ChocoChock01 On the road aagaain See Rallies below;

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    What temp. was it outside?


    Where was the thermostat set at??
     
  11. pej

    pej Member

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    The problem is that your furnace has failed to light. The control board on the furnace is not very smart. It tries three times and if it fails to light then the fan continues to run forever until you turn it off at the thermostat and turn it back on.

    See page 16 of the service manual for a full description of the starting sequence.
    http://bryantrv.com/docs2/docs/hflamefurn04.pdf
    Lots of other good info in this document!!

    Beyond the basic issue of running out of propane, in my experience, three things cause the igniter to not light getting you into this state.

    The first was issues with the igniter. I carefully removed mine and polished the electrodes with sand paper and steel wool. I also adjusted the gap. Following this, the igniter started the furnace of the first snap. (Done twice in 15 years of operation.)

    The second is a low battery. While the furnace will run even if the battery is down to 11 volts(really low!), the igniter does not produce a great spark and will not always light. Keep your battery above 12v or run off the converter.

    The third issue is switching to a digital thermostat. While I enjoy better temp control without wild overruns, the digital thermostat runs the furnace for shorter periods of time and therefore restarts more frequently. The igniter does not light as well when it is still hot which is the case with a quick restart on a cold night.

    And to restate, if the furnace does not light after three tries, you must turn down the thermostat until the fan stops and then turn it back up to try again.

    Enjoy the heat.

    Peter

    PEJ
    2001 Palomino Pony 21/2011 Ford Escape
    headpond.ca/Palomino.html
     

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