furnace fan
Put my fifth wheel away for the winter and the furnace fan won't shut off. No propane on, just battery. Any ideas what the cause might be?
Forum Discussion
dougrainer wrote:mchero wrote:
The Hi limit switch on my Atwood furnace is normally CLOSED, opens when overtemp condition.
From the Atwood service manual;
The limit switch is an in line safety device which protects
the furnace from any over heating conditions. The
contacts in the limit switch open at a given temperature
setting, shutting off power to the valve
Once the burner shuts off, the fan continues to run to cool the chamber down. Once the Limit closes, the fan will shut off. This can happen from normal operation when the burner chamber gets too hot, but the wall tstat has been satisfied. The wall tstat if still calling for heat, the Limit will open if the chamber gets too hot and will then close again once the chamber is cooled down and the burner will then come back on. If you have reached the tstat setting , the odds are the Limit is now OPEN from the chamber heat and will run the fan until the chamber cools down enough to close the limit switch. Doug
Again, we don't even know the make and model of the furnace in question. BUT: The Atwood Service Manual description of high temp limit switch function is correct for any Atwood or Suburban furnace made in the last 20 or 30 years. The high temp limit switch has NOTHING to do with the fan operation in these furnaces. That is controlled by the time delay relay on earlier furnaces or a relay on the circuit board on newer furnaces.
Some really old furnaces had a bi metal switch that allowed the fan to run long enough to cool down the furnace.
