How to choose the heat pump for your swimming pool?


Warm up (or cool) the water in your pool at will by capturing the calories free of charge, represents a revolution in access to the pleasure of extending the time of use of this leisure equipment, sometimes also used for therapeutic purposes. The operating costs of swimming pool water temperature control systems have long held back the expansion of this practice. The swimming pool heat pump, (PAC), changes the situation so much, that the offer becomes bloated! The purpose of this file is to help you gather the best arguments to inform your personal choice.

7 criteria defining the performance of the CAP

Installing a heat pump consists of grafting a new accessory onto a set of pre-existing elements. For the graft to take, many interactions predictable will have to be linked together in an efficient and harmonious manner. The first task therefore consists in making a precise inventory of the technical and environmental characteristics of the equipment in question. These data make it possible, in particular, to assess the predictable heat losses, for the calculation of the power heat pump necessary for the correct balance of the system. Note therefore:

  • The volume approximate pool size (L x W x H average water), expressed in m3
  • The type and the manufacturing method of the swimming pool (above ground, buried, masonry, concrete, stainless steel, wooden structure, synthetic material, etc.). Special attention must be paid to the existence and nature of any pond isolation devices
  • Theexposure of the swimming pool (no shade, indoor, outdoor or covered pool)
  • The air-conditioned areaof the site and the risk of strong and / or frequent winds
  • The maximum temperature of the pool water in degrees Celsius
  • The heating period, expressed in months
  • The filtration circuit flow rate, to adjust the heat pump efficiency

4 essential technical performance criteria for the preselection of your heat pump

The problem is to sort between the different models of swimming pool heat pumps compatible with your site and your requirements. This first choice, of a purely technical and functional nature, is based on the criteria published by the manufacturers for each of their productions, namely:

  • The power (in kW), sufficient to provide the calorific needs
  • The COP, ratio between the electrical quantity actually consumed and the quantity of calories returned
  • The acceptable sound level
  • The ancillary functions essential to ensure continuity of service, such as automatic defrost in case of frost
  • In the horizontal heat pump, the very cool air flow from the fan blows horizontally. This very European configuration turns out to be troublesome if the heat pump is placed near the bathing area. It is therefore necessary to carefully define its orientation
  • In the heat pump vertical, the ventilation blows upwards, which makes it less noisy. On the other hand, it is more bulky, often more expensive and exposed to the falls of various objects in the space of the blades.

Choose the type of swimming pool heat pump

Two types of swimming pool heat pumps with broadly the same performance coexist on the market:

Each type exists as a variant reversible, to cool the pool water during heatwave periods. It is the certainty of finding, in all circumstances, a constant temperature of the bath water. For both, the trendy option is the remote control allowing the heat pump to be moved or hidden without hindering its use.

Choose the right power rating

The relevant calculation of the power of the swimming pool heat pump is fundamental. This sizing depends on the good operating and performance conditions of the system:

Undersized, the pool water takes a very long time to reach or, depending on the circumstances, does not reach the desired temperature

Oversized, the excessively rapid rate of operating and interruption cycles imposed on the compressor accelerates its aging, which is the cause of premature failure.

These two situations generate disproportionate costs of acquisition, installation and operation, as well as functional inconvenience destroying all or part of the interest of the CAP. In order to qualify this difficulty, each machine is capable of working in a power range more or less wide. This allows the use of simple calculation formulas giving a sufficient approximation, such as V x C x E, or :

  • V – is the volume of water in the basin in m3
  • VS – is the desired temperature rise coefficient
  • E – is the sunshine index of the region concerned

Concretely, for a 50 m3 swimming pool, located in Marseille (sunshine index 1.8), a daily temperature rise of 2% (coef 0.12), the nominal power of the heat pump is: 50 x 1.8 x 012 = 10.8 kW

NB : to help consumers compare what is comparable, the federation of swimming pool professionals (FPP) and French standards (NF) require manufacturers to display the power of their equipment under the following operating conditions: an outside temperature of 15 ° C; a pool water temperature of 26 ° C; a hygrometry rate of 70%.

In practice, the power curve of each device evolves outside this strict framework, under conditions which are specific to it, which complicates the difficulty of choosing the right compromise.

The temperature rise in the pool is slow. Count from 1 to 3 degrees per day on average depending on weather conditions and the presence or not of a night cover system. To overcome this drawback, some manufacturers offer an electric heater. This additional resistance (integrated into the heat pump or independent) provides additional calories during the only temperature rise phase, then turns off. Obviously, during these few hours, electricity consumption skyrockets! However, this system makes it possible to limit the nominal power of the heat pump and therefore reduces the initial investment and operating costs for the rest of the season. Here again, no generality is applicable. The balance sheet relevant is closely linked to the specific conditions of each installation and to swimming pool usage habits.

The coefficient of performance (or COP)

The main originality of heat pumps lies in their power to restore more energy than they consume. The COP is the ratio between the quantity of electricity, in Watts, consumed by machine and the quantity of thermal energy, always in Watts, returned to the heating circuit. By way of comparison, a swimming pool heat pump with a COP of 6 consumes 1 kW of electricity and releases 6 kW of heat, while an electric resistance radiator that consumes 1 kW releases only 1 kW. The value of this report is specific to each material, of which it characterizes the yield. The COP should not be confused with the COPA, a similar ratio, but applied to the entire installation, taking into account the impact of ancillary accessories. The COP and COPA fluctuate according to the heat pump model, the outside temperature and the desired setpoint temperature.

Given the number and complexity of the elements involved, the use of the services of a professional is strongly recommended for the final calculation of the power adapted to the needs of your installation.