Swimming pool heat pumps (heat exchangers)
When it comes to heating a swimming pool, a heat pump has the lowest running costs of any swimming pool heating system. Indeed it is claimed that, for every kilowatt of energy used, the pump will produce between 4 and 5 kilowatts of usable energy. This means that, whist heat pumps do not have the lowest initial outlay, they do prove very economic over time.
How does a heat pump work
Using a heat pump is possibly the most advanced way to heat your swimming pool. The heat pump system uses a process called energy transfer to transfer the heat in the atmosphere (air) directly to the swimming pool water, thereby brining up the pool temperature.
It does this by utilizing a refrigeration system in the form of a coil (an evaporator air coil) which contains the liquid refrigerant. In simple terms, this coil acts as a heat collector.
This refrigerant liquid absorbs atmospheric heat and is converted into refrigerant gas which is compressed (by the pump), causing it to condense. This process produces heat which it then passed into the swimming pool water using a heat exchanger. As this transfer takes place, the refrigerant returns to a liquid state and the process is repeated.
The easy way to think of a heat pump is like an air conditioning unit in reverse.
Advantages of a heat pump to heat a swimming pool
Heat pumps have many advantages over alternative pool water heating methods.
- Firstly, they have very low running costs making them cheaper to use than gas or electric pool heaters.
- Secondly, heat pumps appear to be able to produce more usable energy than they actually consume. Most figures suggest that, for every unit of energy that they use, heat pumps produce 4 to 5 time more usable heat energy.
- Thirdly, because of their low energy usage, heat pumps are environmentally friendly. Only a solar heating system can claim to have a smaller environmental footprint.
- Finally, heat pumps are ideal if the pool's heating system needs to be operational for long rather than short, or intermittent, periods of time. This kind of heating system works best when maintaining an already achieved pool temperature.
Heat pumps rarely require maintenance and the refrigerant in the system should last for the lifetime of the product.
Disadvantages of heat pumps
The main disadvantage of a heat pump is its slow heat-up time. Because the heat pump uses a heat exchange system to warm the pool water, it can take a long time to bring the water temperature up to the required level. This means that you need to plan the switching on of the heater well in advance of use.
Heat pumps work best when the margin between the ambient water temperature and desired swimming pool water temperature is small. The greater the margin between these two temperatures, the greater the amount of time require to attain the desired level of heat. This condition is far less restrictive in the case of say a gas or propane heater.
Because heat pumps utilise the air in the environment, they do require a minimum ambient air temperature which is generally regarded as 5 degrees centigrade. At lower temperatures the heat in the air is insufficient for the pump to produce usable heat.
Ideally, a heat pump should be as close to the swimming pool as possible and never more than 10 metres away.