In cool weather, the heat for your RV can come from many sources. The main types of heating appliances are the catalytic heater, space heater, forced air furnace, hydronic hot water heat, and underfloor radiant heat.

The catalytic heater uses a catalyst that converts a fuel such as kerosene, white gas, or propane to provide heat without flames. For the catalyst to work, it needs to be heated first with a low flame, and then it uses oxygen from the air to maintain combustion of the fuel. Many of us have used a Coleman catalytic heater as supplemental heat in a tent camper. After filling its fuel tank, we would take it outside, pour a small quantity of fuel on the catalyst, set fire to the surface, and when the flames died down, and the surface had a soft glow, it was safe to take it inside the tent for the night. The tent has enough air leaks that it provides no danger to the occupants from a lack of oxygen in the air. When a catalytic heater is used in a travel trailer or motorhome, it is important to remember to open a roof vent at least one inch high to allow enough fresh air to enter so that the oxygen in the air is not depleted. The big advantage of catalytic heat is that it does not require the use of precious 12-volt battery power when dry camping. More modern catalytic heaters available in Canada, that have adjustable output from 1500 to 7600 BTUs, are built by Northstar and Olympian and are permanently mounted on a wall near the doorway of the RV. (Top)

The next advance in heater technology was the space heater used in many smaller trailers. This was fired by propane in a closed combustion chamber that took its combustion air from the outside of the camper. It had a thermocouple safety device to shut the main gas off if the heater pilot light flamed out. A copper tube filled with an inert gas was located near the floor to sense the temperature of the air in the camper. This was connected to the propane valve so that when the gas inside the tube expanded after the room warmed up, it would shut down the supply of propane to the main burner. When the temperature went down, the gas inside thermostat tube would contract and allow the propane valve to open so that fuel would flow again to the main burner and be lighted automatically by the standing pilot flame. This type did not require any 12-volt connections as it had no blower to move air around the unit, so it was ideal for boondock camping.

As Rvs became bigger, heaters were built that produced more BTUs of heat, and blowers and ductwork were added to distribute the warm air to distant corners and increase our comfort level. When the 12-volt thermostat called for heat, it would open the propane valve to allow fuel to flow to the main burner. This type of furnace still used a standing pilot flame to ignite the main burner. This furnace took its combustion air from outside the trailer so it was not necessary to keep vents or windows open to let fresh air in. If your floor heat registers were closed off or covered by carpets, they would prevent the warm air from getting out of the ductwork and the combustion chamber could overheat. If this happened, a safety thermal cutout would shut off the gas supply. Since the thermostat of this new furnace could not sense whether heat was needed without the 12-volt battery power, and the blower needed the 12-volts to distribute the heated air through the ductwork, this caused a lot of campers to look for electrical sites in campgrounds to prevent their batteries from runnning down during the night. As technology content increased, furnaces had an electronic circuit board included that would control the propane valve and start the flame in the main burner with an electrical spark. This is called the Direct Spark Ignition system. (Top)

The introduction of Direct Spark Ignition did away with the need to lie on the floor to light the pilot flame with a match or piezoelectric sparker. Since there is no pilot light anymore, this conserves a small amount of propane fuel. When the 12-volt thermostat called for heat, the blower would run for at least 30 seconds to bring in fresh combustion air from the outside and purge the combustion chamber of any left over gases. Then the electronics would open the gas valve and create the spark needed to ignite the gas. If the flame did not ignite, special electrodes that were in the flame path would send a signal to the ignition board to safely shut down the gas supply from the main valve. These newer furnaces still have the high temperature thermal cutouts that will safely shut down the furnace if the combustion chamber becomes too hot because the hot air is not able to flow properly through the ductwork. It is very important not to cover the registers or shut them off with the control levers. These registers should be redesigned so that the lever can move enough to redirect the heat, but not shut off the air flow entirely. Some trailers and motorhomes use tubular heat ducts with a coiled wire inside to keep them round. However, you have to be careful not to crush these ducts by storing objects on top of them.

Some newer motorhomes have a hydronic heating system, similar to hot water heating in old houses. Since the water in the lines could freeze when the furnace was not operating in cold weather, a solution of antifreeze is normally in the lines, or you would have to completely drain them to protect them from freezing. The heat for this solution comes from either a diesel or propane fired boiler system. Then the heated solution is forced through small radiators distributed throughout the motorhome by a 12-volt pumping system. Some of these radiators have 12-volt blowers attached so that air can be drawn across the fins to produce a flow of heated air in different areas of the coach. (Top)

Many of these systems also can be connected so that hot water flows through the block of the diesel engine to preheat it for better starts on a cold day, and to heat the water normally used for showers and washing with the use of a heat exchanger on the regular hot water heater tank. This system needs to anticipate sudden demands for heat by starting the boiler as soon as the outside temperature drops or cold air enters when someone opens a door to the outside.

A new concept in heating is showing up in higher priced motorhomes and bus conversions with radiant electrical heating similar to that used in some houses. Electrical heating panels are installed under the floor surfaces that produce heat from the electricity provided by the 12-volt system, the auxiliary generator or from the electricity in the campground. Heating pads can also be placed under each holding tank, and on any water or drain pipes that might be exposed to cold air.

Any type of heating is welcome when the weather turns cold and we want to extend our camping season earlier in the spring, or later in the fall. Some people even equip their Rvs with double pane windows and an optional extra insulation package so that they can enjoy their favorite ski resort. (Top)