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The route of the refrigerant through the heat pump in heating mode
The refrigerant meets the outdoor air in the evaporator (heat exchanger). The air is drawn through the evapora-
tor by a fan located on top of the heat pump. The refrigerant, which was previously in a liquid state, will evaporate
in this process. The pressure is low and heat is required. Heat is taken from the outdoor air. A sensor in the
expansion valve (6) ensures the evaporator utilises as much of the "free energy" as possible before the refrigerant
(in a gas state) is led into the compressor.
The compressor increases the pressure of the refrigerant. The temperature of the vapour reaches approximately
+100ºC. The warm gas is then led into the condenser.
The condenser is the heat pump’s heat emitting part. In the condenser, which is a fully soldered heat exchanger
in stainless steel, the refrigerant (gas state) meets the water from the heating system (radiators and fl oor coils).
When the warm gas is cooled by the circulating heating water, it changes into a liquid state (condenses). Energy
is emitted in this process to the heating system or the hot water. After the condenser, the refrigerant, which is
now in liquid form, continues through a drying fi lter.
The drying fi lter is used to collect any moisture in the system. After the fi lter, the refrigerant passes through a
sight glass.
The sight glass is used to check the level in the system. There should be no bubbles in the sight glass during
normal operations. However, there might be bubbles when the heat pump is started and stopped or during
defrosting. After the sight glass, the refrigerant continues on to an expansion valve.
The refrigerant pressure is lowered in the expansion valve. This also causes the temperature to drop. When the
refrigerant has left the valve and passes the evaporator it changes to vapour again. This completes the refrigerant
circuit. The expansion valve is equipped with a sensor (bulb) just before the compressor. The sensor controls the
amount of fl uid entering the evaporator.
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2
3
4
5
6
1
2
3
4
5
6
Heat transfer fl uid out.
Heat transfer fl uid in.
Refrigerant fl ow in heating
mode.
Refrigerant fl ow in defrost
mode.
Service
connec-
tion
Non-return
valve
Suction accumulator
Bulb
Pressure
switch
low
Service
connec-
tion
Pressure
switch
high
4-way valve
How a heat pump works
Service
connec-
tion