Put simply a Heat pump takes the available heat from the ground or air surrounding a property and increases it to a more useful temperature for use in the home. This renewable source of heat can be used to create warm air or water (for space and central heating) as well as hot water (for both central heating and domestic hot water supply).
It achieves this by taking the same principle that allows a fridge to cool your groceries and by utilizing it in reverse.
A heat pump operates in the following way:

1. The source of heat, which can be outside air or a water mix which is contained within ground collectors, is either blown or pumped over the Heat Exchange Surface of the outside part of the heat pump.

2. This heat (although cold in comparison to a homes internal air) is warm enough to cause the special refrigerant liquid to evaporate and turn into a gas.

3. This gas is then put through a compressor which increases the pressure of the gas, a factor that causes its temperature to rise. For example you may have noticed that a bicycle pump, gets warm when it is used, the gasses in a heat pump experience the same temperature rise due to compression.

4. The gas (now heated) is passed over the internal heat exchange surface. This heat can then be either blown around a property or be transferred into a home’s central heating or hot water system.

5. The gas falls in temperature as the heat is transferred into the home and it subsequently returns to a liquid state.

6. The refrigerant returns to the outside heat exchange surface and the process repeats itself until sufficient heat is passed into the home.