Solar System for Heating Swimming Pools

Swimming pools are an ideal application for a solar water heating system, as the
temperature required is quite low - under 30°C. It can dramatically decrease - and in some cases eliminate - pool heating costs with a 2~5 year payback time being realistic.

We know that when properly sized and installed, a solar pool heating system in the UK will provide 5°C ~ 10°C over an unheated pool from May ~ September each year. Generally that means you can be swimming in water at a temperature of 25°C to 30°C for five months.

If you don’t already do so, you should start to use a floating pool cover at night and when the pool is not in use to reduce heat losses.

Empirical data shows that evaporation and radiation losses amount to 0.423KW/m2h with pool water at 25°C to 30°C in still ambient air at 15°C. A 5 x 11m pool (55m²) will thus lose 23KW/h due to evaporation and radiation losses. It is always easier and cheaper to conserve heat energy than to generate it so use a pool cover as much as possible.

We’ve done all of the calculations and designed solar heating kits for swimming pools of common sizes so that you have only to select the solar heating kit appropriate to your requirement. The kits have the correct specification, sizes and quantity for each component in the system to ensure that it will meet the design conditions.

We supply everything that you need directly to your door and there is no need to source plumbing materials and fittings for the solar circuit locally. However, we don’t supply pipe work or components for the pool water system.

Assessing requirements

Calculation of heat exchanger requirement is based on volume (m³) whilst solar panel requirements are based on area (m²) because heat absorption is based on surface area (m2) and so are radiation losses.

The heat exchangers will extract more heat (up to 68KW from water at 20°C ~25°C) than the solar panels can deliver and flow rates through the solar panels should be set as high as possible.

The model 5113-5 heat exchanger is suitable for pools 25m³ ~ 99m³ (5000 gallons ~ 20,000 gallons) and the 5114-5 model is suitable for 100m³ ~ 150m³.

The pool pump will govern the pool water flow rate and there is no need of a separate pump for the pool heating system.

As a general rule, the area of solar heating panels should be equivalent to around 30% of the pool surface area. If expense is no object you can increase the number of solar panels (just buy a larger system) to obtain greater power output from the solar heating system.

The wetted parts of our swimming pool heat exchangers are made from corrosion resistant materials suitable for use with chlorine water, seawater, therapeutic and spa pools. Please note that corrosion resistant does not mean corrosion proof. All materials will eventually suffer degradation over time in the presence of corrosive materials and these heat exchangers are no exception.

Always maintain pH to within the correct range. The ideal pool pH is 7.4 to 7.6. On no account should it fall below 7.2 or above 7.8. We recommend use of an automatic pH controller as may be seen in the photograph below.

Ensure that the chlorine levels are within the range recommended by the chemical manufacturer.

The heat exchangers are very easy to maintain. Uniquely to this design, both the end covers and tube stack can easily be removed for cleaning purposes.

These swimming pool heat exchangers are generally suitable for pools up to 228m³ (50,000 gallons) for solar installations. For larger installations please contact our sales department.

Solar heating systems up to 60m² (96m³) all employ the smaller 5113-5 model heat exchanger and the larger systems employ the larger 5114-5 model. Both heat exchangers incorporate an integrated thermostat pocket to house the temperature sensor for the MSR 01 solar controller.

Installation Advice

The system design is inherently simple. The solar primary circuit will be a closed loop with a solar heat transfer fluid circulating into and out of the swimming pool heat exchanger via a solar pump station.

The heat exchanger has ¾” BSP FI connections for the solar primary circuit and is supplied with solvent weld connections with 48mm and 50mm diameter collars (to suit UK and European applications) for the pool water circuit.

Heat exchangers should be installed downstream of the pumping, filtration but before any chemical dosing equipment. Under no circumstances install the heat exchanger downstream of a chlorine generator or automatic pH correction dosing inlet.

This photograph shows a typical pool room with chlorine generator and automatic pH control. The pipework will have to re-arranged if a heat exchanger is to be installed. The short distance between the 5-port valve and the chlorine generator will have be extended by adding pipework into which the heat exchanger can be fitted.

Circulation of the heat transfer fluid in the pressurized solar loop is controlled by the MSR solar controller. The temperature sensors being installed in the thermostat pocket of the heat exchanger and the solar panel manifold.

You should set the MSR solar controller to give the maximum temperature differential possible (usually 15°C).

Photograph below shows exploded view of the swimming pool heat exchanger.