Swimming Pool Heat Exchangers

If your pool isn’t heating up to the required temperature, there are a few possible causes. Using this checklist could help you locate the problem:

1: Do I have enough energy?
Whether heating your pool with a gas boiler, solar panels, a heat pump, or another energy source, it is important you have enough energy to do the job.

2: Do I have the right heat exchanger?
A common misconception is the larger the heat exchanger, the faster it heats the pool! However, this isn’t necessarily the case. There are many types of heat exchanger used to heat swimming pools and they differ dramatically in design, performance and heat transfer efficiency.

3: My heating system is adequate but my pool still fails to heat up!
Flow rates of both the hot and cold fluids are vital for the heat exchanger to transfer thermal energy to the pool. If the hot water flow rate is too low, the available energy will not be passed through the heat exchanger. However, the flow rate of the pool water is equally important.

4: And if you’ve done all that…
Even if all the equipment is adequately sized, there may still be other parts of the system creating issues that will need to be checked.

5: In summary…
This is a summary of a more detailed article designed to help identify problems with pool heating and heat exchangers. Read the complete article here.

More product information on Bowman swimming pool heat exchangers.

Swimming pool heat exchangers work by transferring heat energy from a hot water circuit, to the cooler pool water circuit, without the two fluids ever coming in direct contact with each other.

Most swimming pools are heated via a boiler, using fuels such as Gas, LPG or Biomass, as the energy source. In theory, the most efficient way to heat the pool water circuit would be to connect it directly to the boiler.

Were this to happen, the chemicals and minerals added to the pool water to keep it safe for use, would quickly erode and damage vital components inside the boiler, leading to premature failure and a costly replacement.

However, by using a heat exchanger to act as an ‘interface’ between the boiler water circuit and the pool water circuit, the boiler is protected from damage and the pool water is quickly heated up to the required temperature for use.

Shell and tube design heat exchangers are extremely popular for swimming pools, due to their efficiency and ease of maintenance. Inside the ‘shell’ there is a bundle of tubes, known as the ‘tube core’, through which the pool water passes in a single direction.

At the same time, hot water from the boiler is circulated around the outside of all the tubes in the tube core. Traveling in the opposite direction to the pool water flow, the boiler water transfers its heat to the pool water, before being recirculated back to the boiler, for reheating.

Both water circuits operate in a continuous heating cycle, until the total pool water volume has reached the required temperature, which is usually around 28 – 30 °C.

Bowman manufactures a comprehensive range of swimming pool heat exchangers for everything from spa pools and hot tubs, up to Olympic size pools.

More information on Bowman swimming pool heat exchangers.

Selecting the correct heat exchanger is very important to ensure the pool heats up quickly to desired temperature. The main issues to consider when sizing a swimming pool heat exchanger are;

1. Pool size – what is the water capacity? Heat exchangers are sized according to capacity, so a unit designed to heat a 80 m³ (18,000 gal) pool would be no use, if you have an 180 m³ (39,500 gal) pool.
2. How is it heated? Usually, the choice is either a boiler or renewable energy. If it’s renewable energy, select a heat exchanger specially designed for the lower temperature water provided by solar panels or heat pumps, as these units need less energy to heat the pool to the required temperature.
3. Boiler water temperature – however, most pools will be heated by boilers, so what is the temperature of the boiler water? Usually, it’s between 80 °C and 85 °C – the ideal temperature for pool heating. Some boilers are lower – around 60 °C. So, using 82 °C water, a heat exchanger providing 110 kW should heat your 180 m³ pool efficiently. But if the boiler water temperature is only 60 °C, the heat available to transfer drops to around 60 kW – a reduction of over 40%, so a larger heat exchanger would be required for the pool to achieve full temperature.
4. What are the water flow rates? Flow rates are vital for the heat exchanger to transfer thermal energy to the pool. If the hot water flow rate is too low, the available energy will not be passed through the heat exchanger. However, the flow rate of the pool water is equally important. People often think it is important to generate a large temperature differential between the pool water entering and leaving the heat exchanger. They are happy, if the pipework connected to the outlet of the heat exchanger is noticeably warmer than it is at the inlet. In reality, this actually reduces the efficiency of the heat transfer process! This is because the pool water flow is too low – the water remains in the heat exchanger for too long, so a much smaller volume of water is being heated to a slightly higher temperature. However, with higher flow rates, the time taken to turn over the pool water will reduce and even a small increase in the temperature of the pool water through the heat exchanger (1.5 °C for example) will have a greater effect on the heating efficiency of the pool.

More information about heat exchanger selection, read the article ‘Why doesn’t my pool heat up faster?’