How Do Air Heaters Work
When the unit is switched on the dosing pump feeds fuel from the vehicle's fuel tank to the heater. Here the fuel is automatically ignited by means of a glow plug. If combustion does not occur immediately the unit automatically repeats the start-up procedure. In the combustion chamber a flame is lit which heats up the heat exchanger. The unit takes air in from outside of the vehicle for combustion purposes and the combusted exhaust air is discharged back outside. During heating, the integrated fan sucks in the air to be heated through the inlet and feeds it through the unit. As the air flows through the heat exchanger it is heated up and is then distributed through the outlet.

The connected hot air ducting spreads the air evenly throughout the vehicle interior. Due to the unit's separation of the combustion cycle from the heating cycle there is no quality impairment of the hot air. A temperature sensor constantly measures the interior temperature and adapts the heating level by automatically adjusting the amount of air passing through the unit. In this way, the temperature selected by the user is rapidly reached and maintained at a constant level. After the unit has been switched off, the combustion process is terminated in a controlled manner. For this purpose the unit briefly goes into re-run mode to cool itself down. It is then immediately ready for restarting.

How Do Water Heaters Work?
Upfront you have to know that "water heaters" at Webasto are coolant heaters which heat up a coolant circle (e.g. like the engine coolant cycle). These heaters do not directly heat up the water which you use in your recreational vehicle! This naming has an historical origin and is actually not meant to confuse you.

When the unit is switched on, the dosing pump feeds fuel from the vehicle fuel tank to the heater. Here the fuel is automatically ignited by means of a glow plug. If combustion does not occur immediately, the unit automatically repeats the start-up procedure. In the combustion chamber, a flame is lit which heats up the heat exchanger. The unit takes air in from the outside for combustion purposes and the combusted exhaust air is discharged to the outside. During heating, an internal circulation pump feeds the water-glycol mixture (coolant) through the unit. As the coolant flows through the heat exchanger, it heats up. In the connected water circulation system, heat exchangers then transfer the energy to the interior and/or the engine. Once the vehicle interior or engine has warmed up the heat requirement is reduced and the water temperature continues to rise. At a pre-set temperature threshold the unit reduces output at this moment or goes into standby mode. The heating procedure automatically restarts when the water temperature drops below a certain level. The unit thus adapts the heat output automatically to the heat requirement. After the unit has been switched off the combustion process is terminated in a controlled manner. For this purpose the unit briefly goes into re-run mode to cool itself down. It is then immediately ready for restarting.