Swimming pool heat exchangers

Heat exchangers can be a cheap and effective option for heating a swimming pool. They are particularly popular with small to medium sized pools where the differential between the ambient pool temperature and the desired bathing temperature is only a few degrees.

How a swimming pool heat exchanger works

Most swimming pool heat exchanges are plumbed into a domestic central heating system running off gas, propane or oil.

The heat exchanger, which is normally made from stainless steel, has two sets of pipes connected to it and running through it.

The first set of pipes takes hot water from the boiler to the heat exchanger and the second set of pipes circulates water to and from the swimming pool.

The system works as the cool pool water draws heat from the boiler's pre-heated water. This is done by means of a series of thin heat conducting metallic plates that allow the exchange of heat (or recovery of heat) from one water flow to another. These plates usually have grooves or channels to maximise their surface area, but they prevent the two flows of water from making direct contact.

A heat exchanger should always have a lower rating than the boiler from which it draws its heat.

There are also specialised stand alone heat exchangers that work with swimming pool heat pumps,
see swimming pool heat pumps.

Why use a heat exchanger as a pool heater

There are a number of reasons for using a heat exchanger to heat (or supplement the heating of) a swimming pool.

Firstly, heat exchangers utilize an existing energy source, in this instance a domestic boiler, and therefore they can take advantage of an existing heat supply at little, or no, extra cost.

Secondly, heat exchangers can be very effective secondary source pool heaters. They work well when maintaining a pool temperature that has already been raised by another pool heater system, and they are often used to supplement a primary heater that is more expensive to run.

Advantages and disadvantages of heat exchangers for swimming pools

Heat exchangers utilize an existing energy source, so their running costs can be low and their carbon footprint is small. This means that the main cost of a heat exchanger is the initial outlay.

Heat exchangers are small and take up a minimal amount of space. They are also cheap to buy and are available in a range of heat outputs that suit different boilers.

Although the running costs and initial monetary outlay of swimming pool heat exchangers are low, heat exchangers do require a considerable amount of plumbing and pipe work. This can involve high labour and parts costs which are not always evident in the "shop floor" value of the heat exchanger unit.

For a heat exchanger to be efficient, it needs to be close to both the boiler and the pool so that heat loss through the pool return pipes is minimised. This is not always practical. Further, the rating of the exchanger is limited by the rating of the boiler, i.e. it is not possible to effectively run a heat exchanger off a boiler with a lower rating than the exchanger.

Heat exchangers are good at raising the temperature of a swimming pool by a few degrees, or maintaining an already elevated pool temperature. They are however limited by the differential between start and required pool temperatures and they are slow at raising the pool water's temperature if no other heating method is used.

Swimming pool heat exchangers offer an excellent way of supplementing another pool heating system and they are good at maintaining, or raising by a few degrees, the temperature of small to medium sized pools.