Heater control with air conditioning and auxiliary heater, function

W83.20-0003-09

1 Motor

2 Transmission

3 Coolant pump

4 Coolant thermostat

5 Radiator

6 Thermostat

7 Heater return

8 Filling volume

9 Expansion volume

10 Additional volume

11 Filler neck

12 Pressure relief valve 1

13 Pressure relief valve 2

14 Heat exchanger

15 Heater solenoid

16 Timer (auxiliary heater)

17 Operating unit

18 Heat exchanger sensor

19 Outside temperature sensor

20 Interior temperature sensor

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21 Auxiliary warm water heater

22 Driver's cab heating/engine preheating switch

23 Expansion valve

24 Fluid reservoir with drier and inspection window

25 Evaporator

26 Refrigerant compressor with magnetic clutch

27 Capacitor

28 Evaporator sensor

29 Air conditioning switch

30 High pressure switch/low pressure switch

31 Engine preheating solenoid valve

32 Check valve

33 Check valve

A Standard coolant circuit

B Coolant circuit for auxiliary warm water heater

C Air conditioning refrigerant circuit

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Task

The task is to manually regulate and electronically control the air in the cab interior. Whereby in doing so the various influencing variables (outside temperature, interior temperature, heat exchanger temperature, evaporator temperature) are also considered. Additionally, during the cold season, and before starting a journey, a pleasant temperature-controlled interior or windows free of ice and non-fogging can be provided by the warm water auxiliary heater.

Function

The coolant pump (3) pumps "cold" coolant through the engine block.

Finally it passes through the warm water auxiliary heater (21) and reaches the front heater in a heated-up state.

Here, a heat exchanger (14) is used to deliver heat to the cab air.

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The heater solenoid (15), which is electronically regulated by the control (17), is used to periodically interrupt the flow of coolant and thus regulate the coolant flow through the heat exchanger. The heater solenoid (15) is actuated by way of a specified-value potentiometer from the temperature setting rotary switch.

The coolant returns back to the coolant pump (3) via the heater return (7). It is mixed beforehand with cooled coolant from the radiator (5). By far the larger part of the coolant does not flow through the heater, but from the engine to the coolant thermostat (4). Depending on the water temperature, this conveys the coolant through the radiator (5) or directly to the coolant pump (3).

In stationary heater mode the warm water auxiliary heater (21) is activated using the time switch (16) (direct switch-on or timer). The "engine preheating" (22) switch can be used to preheat the engine instead of the interior.

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The refrigerant compressor (26) driven by the engine sucks in the refrigerant vapor and pushes it to the condenser (27). The airstream flows through the condenser (27) located upstream of the coolant cooler (5) and cools the refrigerant vapor, which is heated and pressurized by means of the compression process, until it is liquified.

The liquid refrigerant then flows into the fluid reservoir (24). The filter drier integrated into the fluid reservoir (24) removes any residual water from the liquid refrigerant, in order to avoid any ice formation.

The refrigerant flows from the fluid reservoir (24) to the expansion valve (23).

The expansion valve (23) located on the evaporator (25) expands the pressurized liquid refrigerant thus reducing its pressure, whereupon the refrigerant is evaporated. The evaporation heat required for this purpose is taken from the air in the evaporator (23). The air is cooled.

The vapor refrigerant is sucked in by the refrigerant compressor (26) and compressed again. The circuit is thus completed.