#
WATER HEATER SYSTEM OPERATION

BME074000000T11

## Water Heater System Starting Conditions

• The water heater system will start to operate when all of the following conditions are met:

  - Engine running (CKP sensor signal)
  - Ambient temperature less than 5 °C {41 °F} (IAT sensor No. 2 signal)
  - Water temperature less than 72 °C {162 °F} (Water temperature sensor)

## Normal Operation

• The CPU in the water heater unit outputs a signal to the blower fan and fuel pump, which then deliver air and fuel to the unit.
• Within the unit, fuel is vaporized and mixed with air, and then sent to the combustion chamber.
• The mixture is ignited, by a spark from the glow plug, in the combustion chamber.
• Engine coolant temperature is raised as it circulates along the outside of the combustion chamber.

1 | Blower fan
2 | CPU
3 | Vaporizer
4 | Glow plug/Flame detection sensor
5 | Combustion chamber
6 | Burner
7 | Water
8 | Air
9 | Fuel

## Full/half Switching

• Depending on the engine coolant temperature, the CPU sets the flame to either full or half strength settings.

1 | Full mode
2 | Half mode
3 | Idle mode

## Fail-safe Function

• When the flame detection sensor detects that there is no flame, the CPU stops operation of the fuel pump.