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How does the Truma Combi heater work?

1 Control panel
2 Gas connection
3 Solenoid valve
4 Combined combustion air/exhaust cowl
5 Combustion air fan
6 Gas burner
7 Ignition electrode
8 Combustion chamber
9 Flame tube with baffle
10 Combustion air fan
11 Heat exchanger
12 Electric heating elements
13 Four warm air outlets
14 Stainless steel water container,10 litres
15 Hot water connection pipe
16 Cold water connection pipe
17 Room temperature sensor
18 HDF thermal jacket

The heater is started and the desired temperature for heating and hot water is set on the Truma Combi LCD control panel (1). The heater is connected to the gas supply of the vehicle via the gas connection (2). The gas supply to the heater is controlled via the solenoid valve (3). The required combustion air enters the appliance through the outer duct of the combined combustion air/exhaust cowl (4) and is fed to the gas burner (6) with the help of the combustion air fan (5). The gas burner, which has two ignition electrodes (7) and a flame rectification electrode, ignites the gas-air mixture in the combustion chamber (8).

The hot exhaust gases are diverted at the end of the combustion chamber on the baffle of the flame tube (9) and flow back between the flame tube of the burner and the inside wall of the heat exchanger. They are fed to the atmosphere via the exhaust cowl (4).

The circulation fan (10) blows the air that is to be heated into the appliance. There, the air flows along the fins of the heat exchanger (11) which ensures optimum heat transfer because of its large transfer surface area. Inside the heat exchanger are additional 1800 W electric heating elements (12). They can be used to heat water and/or warm air alternatively or additionally. The warm air is then distributed in the vehicle via four warm air outlets (13).

Fresh water is in the outer stainless steel water container, which holds up to ten litres (14). It is heated by the heat transfer from the heat exchanger (11). Because of the eccentric shape of the water container, the warm water circulates, which ensures optimum mixing of the water and better thermal stratification. The warm water connection pipe (15) connects the Truma Combi with the hot water lines in the kitchen and bathroom. Cold water is pumped from the freshwater tank via the cold water connection pipe (16).

The room temperature sensor in the vehicle (17) measures the air temperature in the vehicle. The water temperature is also measured by internal temperature sensors. The appliance reduces the heat output before the desired heating and water temperatures are reached. When the set temperature is reached, the burner switches off. When the temperature falls below the set heater and water temperatures, the Truma Combi switches on again automatically to heat air and water (winter mode). In summer mode it is possible to heat up the water independently of the space heater. The HDF thermal jacket (18) provides good insulation for the Truma Combi heater.