Heater circuit function

N83.20-2215-79

The heating circuit is connected to the cooling circuit of the engine (M). The following components are connected to the cooling circuit:

 Radiator expansion tank (21)

 Coolant pump (22)

 Thermostat (23)

 Radiator (24)

 Engine (M)

In the warm-up phase and during normal engine (M) operation, the coolant is delivered by the coolant pump (22) via the coolant feed (D) to the engine (M) coolant pipes. The coolant is heated up in the engine (M) coolant pipes. The thermostat (23) remains closed until the coolant reaches a certain temperature. When the thermostat (23) is closed, a small quantity of coolant flows over the heater feed line (B) to the heater heat exchanger (16) and from there over the heater water return line (A) back to the coolant feed line (D). The remainder of the coolant flows from the closed thermostat (23) via the coolant return (E) to the radiator (24) and from there back to the coolant feed (D) via the coolant pump (22). If the coolant reaches a specific temperature, the thermostat (23) opens and a specified volume of coolant is pumped over the heater water feed line (B) to the heater heat exchanger (16) and from there over the heater water return line (A) back to the coolant feed line (D).

The heater heat exchanger (16) is connected to the heater circuit. The cooling circuit is divided into the following sections:

 Heating water return (A)

 Heating water feed (B)

 Vent line (C)

 Coolant feed (D)

 Coolant return (E)

A fixed quantity of coolant is also delivered via the coolant return (E) to the radiator (24) and from there back to the coolant feed (D) via the coolant pump (22). The radiator expansion tank (21) compensates for any possible coolant loss in the coolant circuit via the coolant feed (D) and keeps the heated coolant at a constant pressure. Any excess coolant is returned from the radiator (24) into the radiator expansion tank (21) via the vent line (C).