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If you want to use your pool in a cold weather or if you want to prolong the swimming season, it is good to think about the installing of a water heating system.
The recommended temperature of the water is about 28°C. There are pools in which the maintained temperature is lower. These pools are used for active swimming. And the pools in which the temperature is constantly above 32°C are used for rehabilitation and therapy.
It is important to know that no matter what heating system you choose, you have to supply with solar/thermal cover. Without this cover you will not be able to achieve good results and you will waste a lot of thermal energy.
There are four types of water heating systems: solar collectors or absorbers, electric heaters, heat pumps type “air-water” and heat exchangers.
To determine which method responds to your needs, it is necessary to know the volume of the swimming pool, which months of the year will be used the pool and the desired water temperature.
The choice of water heating system depends also on the source of thermal energy, which you intend to use.
Heat pumps type “air-water”, electric heaters and the solar absorbers are autonomous systems, which are directly connected to the pool, while the heat exchanger needs additional source of heat, for example central heating, solar collectors.
Below we will show you the advantages and disadvantages of each water heating system.
Heat pump type "air - water"
Recently the heat pumps started to become more popular, thanks to its high effectiveness and economy.
From a technical view of point the heat pump represents a refrigerator with the difference that the heat pump uses the heat to warm the water in the pool. The heat pump takes the heat from the air and transmits it to the water in the pool through a heat exchanger installed in it.
Most heat pumps operate at the minimum air temperature of +5 ° C. There are models that work at lower temperatures, for example - 10 ° C. They are used for swimming pools, which are used year-round.
What is the energy consumption of the heat pump?
Exapmle: We have a pool with a volume of 40 m3. We want to increase the degrees of the water by 10 ° C for 40 hours. The pump we use has a capacity of 10kW. The efficiency is 4.6.
In this case the cost for electricity of the pump will be 2,2kW. We received this value as follows:
10 kW (capacity): 4.6 (efficiency) = 2.2 kW
Currently 1 kW/h energy in Bulgaria costs 0.13837 leva (daytime rate).
You get the following calculation: 0.13837 leva x 2,2 kW x 40 hours = 12.18 leva. For this amount we will warm a pool with a volume of 40 m3 by 10 ° C for 40 hours.
You receive this amount when the air temperature is 15 °C. If the air temperature is above 20° C the efficiency of the hat pump will increase and respectively the cost of electricity will decrease.
What is the efficiency?
The efficiency is the correlation between the energy consumed and the energy given by the heat pump. The higher the efficiency is, the more effective the heat pump is and the smaller bills for electricity you will receive.
The qualitative heat pumps have an efficiency of 4 or 5, which means that for one kW/h electricity consumed they give 4 or 5 times more heat of the pool water.
It’s very important to bear in mind at what temperature the heat pump achieves the efficiency of 4 or 5. Most producers specify the efficiency of their pumps at an air temperature of 15° C. Keep this in mind when comparing heat pumps, because some of the dealers could mislead you saying that the efficiency is at air temperature of 24°C.
Selecting a heat pump
When you choose a sand filter system, as well as heat pump, it is better to choose more powerful model to ensure the qualitative pool water heating. The more powerful heat pump will heat the water faster and will bring even more economy.
In the table below are shown the approximate guidelines for choosing a heat pump, depending on the volume of the pool.
Volume of the pool
kW heating capacity of the heat pump
30 – 40 m3
min. 9 кW heating capacity
40 – 60 m3
min. 12 kW heating capacity
50 – 80 m3
min. 16 kW heating capacity
When you compare the values of the heat pump to select the most suitable, it is important to compare under the same conditions, i.e. in the same air temperature and water temperature.
Heating capacity is the energy that the pump gives to the water in the pool. This energy depends on the air temperature, water temperature and the air humidity.
Another important value is the efficiency explained above.
How many hours a day has to work the heat pump?
The heat pump is connected directly to the filter system. When it works, also works the heat pump. For a good effect of the heat pump, the filter system should work at least 12 hours a day. It is better to follow this formula:
the desired water temperature : 2 or for example 28 ° C: 2 = 14 hours / day.
Where can be mounted the heat pump?
The choice of a suitable place for mounting is very important, because the heat pump absorbs and gives a huge amount of air. That is why it is necessary to be mounted outdoors, as in front of it must have at least 5 m free space.
The heat pump must be connected to the circle of the pool water and must be mounted after the filter system.
To prepare it for the winter, drain the water in the heat pump and cover it.
The qualitative heat pumps have titanium heat exchangers, which resist without problems to the availability of chlorine, bromine, ozone or salt in the water.