Heat Pumps for Swimming Pools

Compressor

Allows compressing the refrigerant (gaseous state) and, therefore, producing heat. It has two connections, the smaller one for gas supply, the larger one for suction.

Condenser

This is the part known as the hot source. It is a heat exchanger, usually a titanium coil, through which the gas passes at a very high temperature thanks to the compressor. This exchanger is coated by a PVC casing through which the pool water passes. The hot gas passes through the condenser. In this exchange, the gas will transfer its heat to the water.

Expansion valve

This valve allows the refrigerant to pass from a high-pressure state to a low-pressure state. The valve generates a significant pressure drop. Therefore, when the gas passes through here, it reduces its pressure from the condensation pressure to the evaporator inlet pressure.

Evaporator or evaporator coil

It is a radiator that captures heat from the environment. The larger it is, the more efficient the heat pump is. The gas is injected into the evaporator at a low temperature (below 0 degrees) and gradually evaporates, absorbing heat from the air passing through the coil. Finally, the cycle restarts at the compressor. Besides these parts, it is also necessary to highlight the fan motor, which is responsible for circulating air through the evaporator coil.

Having understood what a pool heat pump is, we can now better understand what the COP is. It is the Coefficient of Performance.

The Coefficient of Performance (COP) is the figure that tells us about the efficiency of the pool heat pump.

It represents the difference between the energy consumed by the heat pump and the energy it returns or provides. For example, if a heat pump consumes 1 kW of electricity and produces or provides 3.1 kW of heat, the COP is 3.1. The highest COP is 7.

It is calculated taking into account different environmental parameters, the outside air temperature, pool water temperature, humidity, etc. As a general rule, the COP is between 4 and 5. A heat pump with a COP of 4 will produce 4 times more energy than it consumes. The higher the COP, the more efficient the heat pump will be.

From one manufacturer to another, a COP of 5 for a pool heat pump will not be equivalent because basic data such as air, water temperature, etc., are not the same. Therefore, we must pay attention to the manufacturers' information and compare it.

One of the most basic aspects when buying a pool heat pump is knowing where to place it. Except for some specific models, heat pumps are installed outdoors, as they need to capture air. Therefore, the back of the pump must be at a minimum distance of 0.5m from the wall or any nearby obstacle.

On the other hand, the front must be at a minimum of 4m from any obstacle or object around.

This is not the only thing to consider when installing a pool heat pump. It is also necessary that the pump is on a completely level surface. Additionally, it would be advisable to install vibration dampening feet (silentblocks) so that vibrations generated during the pump's operation are cushioned.

Finally, it should not be forgotten that each pump model will require a minimum outside temperature to operate. When buying a pool heat pump, you must check the working temperature range, generally they cannot operate when the outside temperature is below 5ºC.

Electrical connection of a heat pump

The pool heat pump will always need power. Normally, a home has a 220v installation, known as single-phase. Although most pumps operate with this voltage, many other models require 380v, known as three-phase.

Besides having the appropriate power for each heat pump model, a dedicated thermal magnetic circuit breaker must be installed in the electrical panel. This device will protect the installation in case of line overheating.

Additionally, it is recommended to include a residual current device in the electrical panel that will disconnect the installation if an electrical leak is detected in any of the pool equipment connected to it.

Hydraulic connection of a heat pump

The heat pump must always be installed after the filtration system, never before. Also, it is recommended to have as few bends and pipe meters as possible so that the system can have sufficient force. The longer the run and the more bends, the less power is used and the greater the heat loss.

In a good installation, a set of bypass valves is also needed. These valves are essential to choose whether the water passes through the heat pump to be heated or, on the contrary, to bypass the heat pump during seasons when heating the water is not necessary.

The heat pump works at full power to heat the water.

When the water is at the desired temperature, the pump works at the minimum power needed to maintain that temperature.

As a general rule, heat pumps usually raise the temperature by 0.5 ºC per hour of operation, so in this case, for a pool of 36m³ (36,000 litres) and with a consumption of 3kW/h by the heat pump, if we want to raise the water temperature from 15ºC to 25ºC (10ºC), we will need 20 hours of heat pump operation.