Use residential heat pump for pool heating?

investigations

čvn 21, 2024

Use residential heat pump for pool heating? | Blog - Microwell

A heat pump as a source of heat, whether for a family house, a company building or a swimming pool, is the cheapest and most available all year round in a suitable climatic zone. Heat pumps are strongly supported and often subsidized in many countries, and their number is continuously increasing. However, we often come across the question of whether a home heat pump is suitable for heating pool water.

Our recommendation is unambiguous and that is to use a so-called "house heat pump" for a house (building, company, hotel...) and use a pool heat pump for a swimming pool. And not to combine the systems.

A domestic heat pump or heat pump "for space heating" is a heat pump that is primarily intended for heating buildings (houses, companies, hotels, etc.) in the form of underfloor heating. On the other hand, a pool heat pump is a special type of heat pump designed exclusively for heating the water of swimming pools, hot tubs, and water attractions. Both of these heat pumps work on the same principle and often resemble each other indistinguishably, but inside they are different in many ways.

Both heat pumps work to exchange heat from air to water for heating and from water to air for cooling. To do this, they use the elementary properties of gases, which when you press you heat them up, on the contrary, when you dissolve them (drain them), you cool them down.

However, the biggest difference lies in the material of the water exchanger. Since the heat pump for underfloor heating of the house works with ordinary water, which is treated with inhibitors to the maximum, it usually uses stainless steel exchangers. This water is not particularly corrosive or aggressive, and therefore stainless steel (or copper) is long-lasting and reliable.

However, a pool heat pump must usually work with high-heat water, which is often treated with chlorine or salt. The lifespan of a stainless steel heat exchanger in this case would not be more than a few weeks, a few months at most. The pool heat pump is equipped exclusively with a titanium heat exchanger. Our ones from Microwell use the purest titanium (99.2% titanium) called "Grade 1".

Differences between home and pool heat pumps can also be found in other areas, but this is beyond the scope of this article. Below in the table you can see a basic overview of the differences.

	Domestic heat pump	Swimming pool heat pump
Water exchanger	Plate - stainless steel	Spiral - titanium
Normal water flow	1.8-3 m3/h	5-12m3/h
	30-50 l/min	84 – 200 l/min
Normal operating water pressure	2-2,5bar	0,8bar
Water circuit	Closed, under pressure	Open
Normal water temperature difference between outlet and inlet	5 to 8°C	0,5 to 1,5°C
100% capacity at conditions	Air -7°C, water 35°C	Air +26°C, water +27°C
DHW heating	Yes	No
Supplementary electric heating	Yes, mostly	No
PV ready	Yes	Yes

If you have already invested in a home heat pump and would like to release its unused capacity into the pool in the summer, you have several options. The most ideal is definitely to let your home pump rest and get a separate pool heat pump.

Since pool water is often highly corrosive, it is out of the question to connect it directly to a domestic heat pump. Damage to the heat exchanger is exempt from the warranty conditions and the repair of the device would be very expensive. There are options to connect the circuit of the home heat pump to the pool through an additional heat exchanger. However, this solution is very little used in practice due to the various technical pitfalls it opens. With additional heat loss and overall reduced efficiency, two completely different caloric units are combined. I mean different energy outputs at a given moment.

Pool heat pumps operate at significantly higher water flows and a lower temperature difference than domestic heat pumps. The difference in flow can be up to 4 times higher with a house pump and the difference in water temperature up to 5 times lower with a pool type compared to a house pump. This results in a problematic setup of the system as such. We can compare it to a top cyclist on a modern bicycle who will try to go at maximum speed in the lightest (lowest) gear.

Building such a system is not impossible, but challenging. A big disadvantage, in addition to additional heat losses and reduced efficiency that another heat exchanger represents, is the fact that you need a home heat pump from September to April. So if you have an indoor pool, your pump simply won't have enough capacity to heat both the house and the pool.

The issue of using a home heat pump to heat pool water is, of course, technically more comprehensive than this article. However, our goal was to convey our unequivocal position and that is not to combine these systems, on the contrary, to purchase a high-quality separate pool heat pump that meets the latest energy requirements and that will provide you with the required comfortable water temperature for pleasant moments in the pool.

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Česká republika	Slovensko

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Use residential heat pump for pool heating?

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