HEATING AND VENTILATION (Description): DESCRIPTION AND OPERATION (page 9 of 10)

HEATING AND VENTILATION

DESCRIPTION AND OPERATION

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Sectioned view of FBH unit

1 Combustion air fan
2 Burner housing
3 ECU
4 Heat exchanger
5 Burner insert
6 Exhaust
7 Glow plug/flame sensor

8 Evaporator
9 Coolant inlet

10 Circulation pump
11 Fuel inlet
12 Coolant outlet
13 Air inlet

The FBH unit consists of:

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A circulation pump.

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A combustion air fan.

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A burner housing.

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An ECU/heat exchanger.

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An air inlet hose.

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An exhaust pipe.

Circulation pump. The circulation pump is installed at the coolant inlet to the FBH unit to assist the coolant flow through 
the FBH unit and the heater assembly. The pump runs continuously while the FBH unit is in standby or active 
operating modes. While the FBH unit is inactive, coolant flow is reliant on the engine coolant pump.

Combustion air fan. The combustion air fan regulates the flow of air into the unit to support combustion of the fuel 
supplied by the FBH pump. It also supplies the air required to purge and cool the FBH unit. Ambient air is supplied to 
the combustion air fan through an air inlet hose containing a sound deadening foam ring.