Heat pump for a pool: how it works, sizing and position

How it works

A refrigerant circulates inside the unit. The fan draws air over the evaporator, where the refrigerant absorbs heat even from cool air. The compressor raises its temperature and, in the heat exchanger, the heat passes into the pool water. In pool units the heat exchanger is usually titanium, to withstand chlorine and salt.

Cold air and condensation water come out of the unit. This water is often mistaken for a leak, so a simple drain is provided under the unit.

What COP means

The coefficient of performance (COP) shows how much heat the unit delivers for each unit of electrical energy it uses. For example, a COP of 5 means that for 1 kWh of electricity about 5 kWh of heat goes into the water. Two things are worth knowing:

• COP is not constant. It drops as the air gets colder and as the water temperature you ask for goes up.
• Manufacturers state COP under specific air and water conditions. Only compare models under the same conditions, and also look at the performance with cool air, which is what matters to you in spring and autumn.

Inverter units adjust their output: they run hard to raise the temperature and then low to maintain it, with better average efficiency and less noise.

How to choose the size

The output is not chosen on the pool's cubic metres alone. The calculation takes into account:

A small unit on a large, uncovered pool runs non-stop and never reaches the temperature. An oversized one heats up quickly, but for no real reason. The calculation is done for your pool and your area. You will find the other options under pool heating.

Position, connection and noise

• The unit goes outdoors with free air flow, not shut inside the plant room, with the clearances from walls that the manufacturer specifies.
• It is placed close to the plant room, so the pipe runs are short.
• It connects after the filter and before the chlorination or salt chlorinator unit, with bypass valves for servicing and for winter.
• The fan and compressor can be heard. Point the air outlet away from bedrooms, terraces and the plot boundary; see also your pool and the neighbours.
• It needs a separate, properly protected electrical line, checked by the electrician.

Cover and operation

A heat pump only works when water is circulating, so it is coordinated with the circulation pump's timer. At the start of the season it usually takes several days of continuous running to raise the temperature; after that the unit simply maintains it.

The biggest gain, however, comes from using the cover every night. Without it, much of the day's heat is lost overnight and the unit has to put it back. How it weighs on the overall picture for your pool is explained under electricity consumption.

Questions

See also