Water, Air & Ground Source Heat Pumps

What is a heat pump condenser? What does it do?

What is heat pump condenser

The condenser is a main component of the heat pump cycle. Once heat from outside is compressed, it passes into a water heating circuit that flows around your home’s radiators. This transfer of heat from the heat pump cycle to the water system takes place in the heat pump condenser.

What is a heat pump condenser?

Take a look at the back of your fridge – you should see a number of metal coils in a grid. These coils transfer heat from inside your fridge to the air outside, and they are the fridge’s equivalent to a heat pump condenser (heat pumps and fridges use the same basic method of heat transfer).

The actual heat pump condenser looks very similar inside; a network of metal ‘heat exchanger coils’ that provide a large surface area for heat transfer to take place.

What does a heat pump condenser do?

As mentioned in the article ‘how does a heat pump work’, there are 4 steps to the heat pump’s vapour-compression refrigeration process. This process is based on a principle that by changing the states of a refrigerant medium (gas to liquid and vice versa), we can control the movement of heat.

When the heat pump is running, refrigerant is constantly circulating through these components that cause the state changes:

  1. Evaporator
  2. Compressor
  3. Condenser
  4. Expansion Valve

Firstly, very cold refrigerant absorbs heat from the air outside through heat exchanger coils.

Then, the refrigerant passes through a compressor. The increase in pressure causes the refrigerant to change state (liquid to gas), which raises the temperature.

In step three, the heat pump condenser passes through another network of heat exchanger coils, transferring heat from the refrigerant cycle to the water heating circuit (or ‘wet heat distribution system’). This heated water then circulates around the radiators and underfloor heating system in your home, giving off heat as it goes.

In step 4 of the heat pump cycle, the cooled refrigerant passes through an expansion valve. The pressure drops, causing the refrigerant to cool and change state (gas to liquid). The refrigerant is now ready to begin the process again.

Heat pump condenser in cooling mode

When your heat pump is in cooling mode, the process reverses. The evaporator and the heat pump condenser effectively swap roles – the compressor passes cold refrigerant through the indoor heat exchanger coils (which in turn runs cold water through your wet heat distribution system), and the evaporator passes hot refrigerant through the outdoor heat exchanger coils, transferring heat outside.

Where is the heat pump condenser?

This will depend on what type of heat pump you have. If you have a monoblock system, the heat pump condenser is found in the fan unit outside. If you have a split system – one with an external unit and an internal unit (a ‘hydro unit’ or ‘hydrobox’) – the heat pump condenser will be inside the internal unit.

How to clean or replace heat pump condenser coils

Heat pump condenser coils aren’t usually a major issue, particularly if you have a split system. In a split system, the heat pump condenser’s coils sit inside your home, so there’s very little chance of debris causing problems as is the case with the evaporator coils.

Your (bi)annual heat pump maintenance contract should prevent anything disastrous from happening, but if your heat pump suddenly starts causing you headaches, call in a professional.

You would need to have a certain level of mechanical aptitude to fix a broken heat pump yourself. There are DIY heat pump fixes online, but attempting to fix the problem yourself may do more harm than good. For instance, you could damage the heat exchanger coils, get an electric shock or void your warranty without any guarantee that this quick fix is going to resolve the problem.

If you want to contact a qualified and professional installer or refrigerant engineer, we’re happy to help. Fill in your details on the ‘Find an installer’ page and we’ll provide you with the details of local experts in your area.

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