Heating Pool Water: Heat Pumps and Solar Collectors

How heat pumps, solar collectors and heat exchangers warm pool water, their pros and limits, and ways to cut heat loss first.

An outdoor pool is warmed by the sun, but that is only enough for comfortable swimming during the hottest weeks of summer. In spring and autumn, when nights are cool, the water cools quickly and the pool sits unused for long periods. A heating system extends the swimming season, and in indoor pools it is essential. The choice depends on pool size, the months of use, available energy sources and attitude to running costs.

Reduce losses first

Before choosing any heating system, bear in mind that most of an outdoor pool’s heat is lost from the water surface, especially through evaporation. In windy spots and on cold nights the loss is even greater. So the most effective and simplest step is to cover the pool when it is not in use.

Other ways to reduce heat loss include:

• siting the pool in a sheltered spot;
• using covers that capture solar heat;
• keeping underground pipe runs short and insulating them where needed;
• setting up ventilation and humidity control correctly in indoor pools.

The lower the losses, the less the heater runs and the smaller the equipment that will do the job.

Heat pumps

A pool heat pump takes heat from the surrounding air and transfers it to the water. The electricity used in the process is considerably less than the heat delivered to the water, so a heat pump is many times more efficient than an electric heater. Its performance figures are stated by the manufacturer at specific air and water temperatures.

Heat pump efficiency falls as air temperature drops. That makes it particularly well suited to extending the season from spring to autumn, while its output is limited in very cold weather. When choosing, check the minimum air temperature at which the unit can operate.

There are several practical points in installation. The unit is placed outdoors with clear space for airflow. Its fan makes noise, so it should be positioned away from bedroom windows and neighbouring houses. It produces condensate water, which needs drainage. The unit is connected after the filter and before the disinfection unit.

Solar collectors

Solar collectors for pools are usually simple polymer panels or tubes. Pool water is pumped through them, warms in the sun and returns to the pool. Their only running energy is the pump.

The main requirements are space and sunshine. The panel area can be comparable to the pool’s surface area and is installed on a sunny roof, on top of a pergola or on a separate spot in the garden. Output drops on cloudy days and in the evening, so solar alone is rarely enough and often works together with a heat pump. In systems not used in winter, panels and pipes must be drained before the frost season.

Heat exchangers and an existing boiler

If the house has a powerful boiler or another heat source, pool water can be heated through a heat exchanger. Pool water does not mix with the heating system; heat passes only through the exchanger wall. The exchanger must be made of a material resistant to pool water and chemicals.

This solution is common in indoor pools and year-round use. However, the boiler must have enough capacity for both the house and the pool, which a heating engineer should calculate. Running costs should also be compared in advance based on gas or other fuel prices.

Controls and a comfortable temperature

A temperature sensor and controller run the heater only when needed. Heating is coordinated with the pump schedule: the heater must not run when water is not flowing. Overheating pool water not only wastes energy but also speeds up algae growth and makes chemical balance harder to maintain.

Selection checklist

• The swimming season and desired temperature have been defined.
• A pool cover is planned.
• Space, noise and condensate drainage for the heat pump are considered.
• There is a sunny area for collectors.
• The boiler’s capacity for the extra load has been calculated.
• Controls are coordinated with filtration.

Zaferoğlu İnşaat decides where heating equipment and plant go as part of the overall house and garden design. You can consult us about space and technical preparation for pool heating equipment.