Worcester GREENSOURCE User Manual page 6

How a heat pump works
The route of the refrigerant through the heat pump in heating mode
In the outdoor unit, the refrigerant meets the outdoor air in the evaporator (heat exchanger). The air is drawn
1
through the evaporator 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
2
+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 brazed heat exchanger
3
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 dr ying fi lter is used to collect any moisture in the system. After the fi lter, the refrigerant passes through a
4
sight glass.
The sight glass is used to check the level in the system. There should be no bubbles in the sight glass during
5
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
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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.
Bulb
Service
Pressure
switch connec-
low tion
2
Suction accumulator
6
1
Non-return
Pressure
Service
switch
connec-
high
tion
4-way valve
Service
connec-
5
tion
4
valve
6
Refrigerant fl ow in heating
mode.
Refrigerant fl ow in defrost
mode.
Heat transfer fl uid out.
3
Heat transfer fl uid in.