Updated August 2021
RV internal and water heating is traditionally via a cylinder in-line with the engine’s radiator. Heated water/glycol circulates through a coil inside the cylinder. That heat is transferred to the water to be heated. The unit works well directly after driving. Water stays warm for about 15 minutes before the engine cools down.
Internal and water heating – via gas
Correctly ventilated LP-gas internal and water heating can legally be used in RVs. They are too big for most camper trailers. For these the most practicable way is via LP-gas and diesel heaters.
Vehicle heating units have been used in Europe since the 1930s. The Webasto and Eberspacher products are almost identical. They have some parts in common. Both companies make products for space heating, and space heating plus water heating. In both, injected diesel oil plus outside air, is burned in a tiny furnace. Exhaust gas is then directed to outside the vehicle.
The Webasto water/space heater. Pic: Webasto Australia.
The air-heating unit’s furnace has an air space enclosed within metal. The burning fuel is isolated from the air that is heated. Outside air is drawn in through the floor. It is blown into the furnace and then into the vehicle.
The water heating unit works much as above. Rather than heating air, a glycol-based fluid is pumped through the furnace. This fluid is heated to a high temperature. It is then circulated through an external calorifier (heat exchanger). There, the heat is transferred to water pumped through the calorifier.
Legally required in Australia, a tempering valve dilutes the hot water with cold water set to 50º C. This prevents being scalded by the 70º C plus hot water.
Space heating is provided by hot glycol being routed to small fan-enhanced radiators. The radiator fans need a 12 volt DC supply. Fuel is supplied by a tiny electric pump. A small panel provides heat control. Both makers offer a 10 litre plastic tank at extra cost.
Some exhaust noise is audible outside the vehicle. This is quietened by exhaust and inlet silencers. The units are still a little noisy while warming up. They are then barely audible.
Even the smallest keeps a camper trailer and its annexe warm in freezing conditions. The dual-purpose versions supply hot water within a few minutes of starting.
Webasto Dual-Top space/water heater self-installed in the author’s Tvan. The radiator-like tank is the water/glycol reservoir. The heat exchanger is the tiny unit at top left. Pic. RV Books.
Gas space heating
Truma’s LP-gas unit works similarly. It is much the same size and weight. Truma states it is approved for RV use in Australia. It generate 2400 watts of heat. LP gas consumption is claimed to be 170 g/h.
As with water heating, gas space heating installation is rigidly restricted. All such appliances may only be installed by licensed gas fitters.
Internal and water heating – risks
Lethal carbon monoxide (CO) is a colourless and odourless gas. It is produced when any carbon-based substance is burned without its combustion being fully complete.
The gas kills because haemoglobin in the blood, that normally transports oxygen, grabs 250 parts of CO in preference to one single part of oxygen. There are only minor indications: headache, nausea, fatigue – then unconsciousness. If asleep at the time, you may never re-awake. It is a ‘silent killer’ and did just that to three caravanners (in Australia) in 2012.
Even at low concentrations, carbon monoxide causes brain damage.
Despite the above being totally known, fools on forums may advise: ‘invert a flowerpot or saucepan over an open gas ring. Others suggest’, ‘turn the gas oven on with the door left open’, or ‘use a charcoal-burning cooking pot as a space heater’.
All of these actions are potential killers, the last especially so. They are all now totally illegal, as too is the act of advising others to do the same.