How A Heat Pump Works; Technology In And Around The Heat Pump - Worcester GREENSOURCE User Manual

How a heat pump works

The heat pump collects heat from the outdoor air
The Greensource heat pump has been manufactured for easy and reliable use as well as
to provide your house with inexpensive and environment friendly heating. The easiest
way to describe how a heat pump works is to say it works like a refrigerator, backward.
In a refrigerator heat is moved from the inside to the outside. In a heat pump the heat, in
the outdoor air, is moved into the house. The heat pump is placed on the outside of your
house. The heat that is in the air, even at temperatures below zero, is converted by the
compressor, heat exchanger and condenser into hot water, which heats your house.
The heat pump will also produce domestic hot water when used in conjunction with the
Greensource hot water distribution unit, which has an inbuilt cylinder for DHW and CH.
There may be very cold days when the heat pump requires additional energy, e.g. at
very low outdoor temperatures. This is obtained from the inbuilt additional electric
heater which is fi tted to the hot water distribution unit.

Technology in and around the heat pump

The heat pump consists of four main parts:
1. Evaporator
Evaporates the refrigerant to gas and at the same time transfers the
heat from the air to the refrigerant circuit.
2. Condenser
Condenses the gas to fluid again and releases the heat to the heating
system.
3. Expansion valve
Lowers the pressure of the refrigerant.
4. Compressor
Increases the pressure of the refrigerant.
These four main parts are linked in two closed circuits. A refrigerant
circulates in the heat pump, which in some parts of the circuit is in a liquid
state and in other parts in a gas state. Read more about the properties of the
refrigerant in the sidebar to the right.
See the detailed description of the technologies used in the heat pump on
the next page.
Boiling point in relation to the
pressure
The boiling point of different liquids
varies with pressure, the higher the
pressure, the higher the boiling point.
For example, water boils at +100ºC at
normal pressure. Double the pressure
and water boils at +120ºC. Half the
pressure and water then boils at +80ºC.
The refrigerant in the heat pump acts in
the same way, the boiling point changes
when the pressure changes. However,
the boiling point of the refrigerant
is as low as approximately -40ºC at
atmospheric pressure. Consequently,
it is also suitable for low heat source
temperatures.
5
How a heat pump works
Note