Before anything else can happen, the heat must first be collected. Depending on the type of heat pump, the heat will be absorbed by a refrigerant either from the ground, air or water source. This takes place in the evaporator with the refrigerant changing from liquid to gas in the process.
The refrigerant is now a gas instead of a liquid and the gas is compressed to increase its temperature even more. It is this heat that can be used to warm up your radiators or underfloor heating.
As the refrigerant transfers the heat that is to be used in your home’s heating system, it gradually cools down and condenses back into a liquid. This occurs in a second heat exchanger. One of the reasons why heat pumps are so efficient is because cooler water from the central heating can continue to absorb the heat from the liquid refrigerant within this second exchanger.
Once the refrigerant has cooled right down, it passes through an expansion valve. In here, the liquid’s pressure is decreased and it returns to the evaporator to begin the whole cycle again.