Christmas is time for weird things going bad at my house. A long story would bring you to the fact that I finally got my propane tank filled yesterday morning. A few hours later I realized that both my furnaces were not working. Fortunately I turned them off and on at the wall switch and both started furn-acing again. Clearly there was a cause and effect here, and clearly it had to do with some sensor or other, but I like to know things. We have had the propane filled lots and lots of times and this has never happened before. So what is the likely cause of this temporary (but immediately very worrisome problem?
First thing that comes to mind is you let them run out of fuel. You say you ‘finally’ got the tank filled. Perhaps your furnaces have a low gas pressure switch that locked them out.
Or, if no pressure switch, they didn’t light off for the same reason (out of fuel) and the primary controls locked them out.
Water in the fuel can cause such a problem, as can drawing too much fuel out at a time in low temperatures. It could cause a pressure drop in the pressure regulator at the tanks, shutting off the furnace and other things. A gas stove will have very little flame when this happens. Pour some warm water over the tank and see what happens (if this reoccurs). If the flame is restored it is either one or the other.
If it’s water in the regulator the gas company will add some methanol which should solve the problem, if you don’t have enough capacity for the temperatures you will need to add another tank (though since this is the first time it happened I doubt that this is the reason unless you are drawing more gas than you did previously, or downsized your tanks)
Yeah, a modern burner control will, among other things, start the pilot and then verify the pilot is lit, then start the main flame,and then verify the main flame is lit. If the pilot or flame isn’t verified, then the control will turn off the gas to prevent gas from filling the combustion chamber. It may do this a few times before locking out for a manual reset. Cycling the power likely acted as that manual reset.
Just had a guy out last week to fix my daughter’s furnace which was doing this. Natural gas, not propane, but she was having trouble with the furnace not coming on overnight and waking up to a freezing cold house. If she turned it off then turned it back on, it would sometimes start working OK but eventually stop again. The furnace guy said it was the flame sensor and described this exact behavior. Got it all fixed up and it’s working great now.