Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club. Today he discusses how an RV furnace works.
Why does really hot air blow out the outside of my propane furnace? —Chiara
Your RV furnace is designed similar to a residential furnace but on a much smaller scale. When the inside ambient temperature reaches the set thermostat temperature, it creates a closed circuit that sends 12-volt power to the module board calling for heat.
The module board then starts the blower motor, which pulls inside air into the furnace through the cold air return and runs long enough to lift the sail switch on the outgoing air shroud. At the same time, the burner assembly pulls outside air from the intake tube blowing it through the burner assembly purging any LP or old fumes through the exhaust vent.
Once the sail switch is lifted, the gas valve opens, the spark ignitor lights the LP, and the flame heats up the burner assembly. This is all enclosed in a series of tubing shown here with a high limit switch monitoring to make sure it doesn’t get too hot:
The heat and exhaust from the burner assembly are exhausted outside as there is carbon monoxide in this mixture just like in your home. The blower motor continues to pull clean inside air through the cold air return and blows it over the top of the enclosed burner assembly and out through either the plenum or hoses to the vents. This way no carbon monoxide or other fumes from a burning flame get inside the rig.
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