Pool heat pumps : Key Data to Consider

Type of Swimming Pool Heat Pump (PAC), COP, SCOP, Energy Class, dB and Noise Levels…: How to Make Sense of It?

Improbable COPs, “world record silence,” flattering SCOPs… Among the multitude of enticing data currently available on the market regarding swimming pool heat pumps, it can be difficult to distinguish the relevant information.

What are the real criteria to consider for optimal water heating? As pool professionals, you need reliable information to best advise your clients.

At POLYTROPIC, we are committed to providing precise and transparent technical data, in compliance with current standards and validated by rigorous tests carried out by independent organizations. As designers of heat pumps for 20 years, our goal is to offer (and guarantee) real performance to enable you to make informed choices for your clients.

In this article, you will find a detailed approach to all the elements you need to know to assess the actual performance of a swimming pool heat pump.

Energy and Noise Performance of Swimming Pool Heat Pumps: Relevant Data to Know

 

 

1. COP: Coefficient of Performance

The COP is a key indicator of a heat pump’s efficiency. It represents the ratio of the thermal energy delivered to the pool water compared to the electrical energy consumed by the pump. The higher this coefficient, the more efficient the pump.

According to Fabrice Granier, Technical Director and R&D Manager at POLYTROPIC, the COP is often highlighted as a major selling point. However, it can vary significantly depending on measurement conditions (air temperature, water temperature, humidity, compressor frequency used)! The standards governing power and COP criteria help ensure transparency and comparability of products.

Indeed, the EN 17 645:2022 standard provides guidelines for determining and communicating these parameters. According to it, the COP must be evaluated under different temperature conditions, as the performance of a pump varies depending on air and water temperatures.

Moreover, even though swimming pool heat pumps are not covered by the EN14 511 series of standards, these are used for the testing method. The test conditions are specific to swimming pool heat pumps and are as follows:

  • Cold condition (Tf): Air temperature at 7°C and 90% humidity, water temperature at 26°C.
  • Medium condition (Tm): Air temperature at 15°C and 70% humidity, water temperature at 26°C.
  • Hot condition (Tc): Air temperature at 26°C and 80% humidity, water temperature at 26°C.

The precision of the measurements and the reliability of the results are crucial; tests must be carried out under the specific conditions defined by existing standards.

Chambre climatique Polytropic  Tests de pac Polytropic dans la chambre climatique  Le banc de test

The POLYTROPIC climatic room and its specific software allow real-time calculation of the delivered power, COP, subcooling, and overheating during tests. Temperature range (°C): from –30 to 60 / Humidity range (%): from 25 to 97 / Air regulation accuracy (°C): +/- 0.3 / Air homogeneity (°C): less than +/- 1 / Air speed on PAC (m/s): less than 1 m/s / Water temperature accuracy (°C): +/- 0.02

 

2. SCOP: Seasonal Coefficient of Performance

The SCOP is a more comprehensive measure of a heat pump’s energy efficiency over an entire season. Unlike the COP, which is measured at a specific moment, the SCOP considers the device’s efficiency over several months, typically from May to September, depending on climatic conditions.

SCOP is a crucial indicator for evaluating the energy efficiency of a swimming pool heat pump. The higher the SCOP, the more the heat pump can produce heat using minimal electrical energy. This results in significant energy savings over the long term, as well as a reduced environmental footprint.

It is determined from the COPs measured under the three temperature conditions mentioned above, applying weighting factors and considering various elements, with the most important being:

  • Outdoor temperature: SCOP takes into account the variations in outdoor temperature throughout the season. It is generally easier for a heat pump to operate efficiently in moderate temperature conditions.
  • Pool temperature: It also considers the temperature to which the heat pump must heat the pool water. The larger the difference between the outdoor temperature and the desired pool temperature, the more the Seasonal Coefficient of Performance can be affected.
  • System efficiency: The quality of the compressor and heat transfer system (evaporator and condenser) plays a major role in the overall performance of the heat pump and thus in the SCOP.

 

Le banc de test  Le banc de test  Le banc de test

SCOP is an excellent indicator of a heat pump’s environmental impact. A high SCOP means the pump uses energy efficiently to heat the pool water, thereby reducing energy consumption and, consequently, the carbon footprint. By choosing a device with a high SCOP, users not only save energy but also contribute to environmental preservation.

Find out more in the article What is SCOP?

 

Note: Different Types of Heat Pumps

The standard distinguishes several types of heat pumps based on their operating capacity:

  • Fixed capacity: The COP is evaluated at the three reference temperatures, and the SCOP is calculated as described above.

  • Stepped models: These adjust their performance on two compressor speed settings. Tests are performed at the maximum compressor frequency for cold and medium temperatures and at the minimum for hot temperatures to obtain COP values. The SCOP is calculated according to the same principles.

  • Variable capacity (or Inverter): These models adjust their power according to needs based on each manufacturer’s logic. New operating conditions are necessary to determine the SCOP:

    • Operating conditions at the maximum compressor frequency for which the maximum power is declared.
    • Operating conditions at the medium frequency (65% of the maximum frequency).
    • Operating conditions at the minimum frequency (30% of the maximum compressor frequency) to avoid declaring COP and SCOP values that are not representative of reasonable real conditions.

The manufacturer must choose between a high maximum frequency to increase the declared power at the expense of the COP and SCOP or a lower frequency, reducing the maximum power but favoring the COP and SCOP. For example, if the manufacturer chooses to use a 90Hz maximum frequency, the tests for the minimum operating condition cannot be below 27Hz.

Reminder: According to manufacturers’ recommendations, a compressor used in a heat pump must maintain a minimum frequency to ensure the machine’s acceptable lifespan.

COP is then determined for each temperature condition:

  • In cold conditions, COP is determined at the maximum compressor frequency.

  • In hot conditions, COP is determined at the minimum compressor frequency.

  • In medium conditions, COP is determined using the following formula:

    COP Tm = D × COP Tm at Min frequency + E × COP Tm at Mid frequency + F × COP Tm at Max frequency

The SCOP for variable capacity heat pumps is determined according to the formula above.

 

 

3. Energy Class

The Fédération des Professionnels de la Piscine (National Federation of Pool and Spa Professionals) has been collaborating with AFNOR and the European Committee for Standardization since 2018 to establish a new standard aimed at promoting more environmentally-friendly equipment. This regulatory framework helps consumers make more sustainable choices for their pools.

As a key player in the market and specialist in pool heating, POLYTROPIC has played an active role alongside the FPP by leading the “heating committee” and contributing to the drafting of the European standard on the environmental performance efficiency of domestic pools, NF EN 17645, dedicated to thermal equipment.

The official logo below must be displayed for optimal clarity:

Marquage de la performance environnementale

This regulation is based on an energy classification system, displayed on each device, to assess its performance. The standard specifies classes from A (most efficient) to F (least efficient) based on the SCOP. A heat pump with a SCOP of 7 or more belongs to class A, while one with a SCOP below 1 would be classified as F.

 

Marquage de la performance environnementale

POLYTROPIC labels all its full-Inverter heat pumps with the energy class A, reflecting their performance and efficiency in full transparency.

 

4. Noise Levels: Calculations and Compliance

In addition to thermal performance, the noise level of a heat pump is also an important criterion, especially in residential environments.

The noise emitted by heating systems in operation has a significant environmental impact on users and the surrounding environment of private family-use pools. Lower noise levels = better user comfort!

The displayed values can be misleading depending on whether they refer to the weighted sound power level Lw (dB(A)) or the weighted sound pressure level.

The A-weighting accounts for the human ear’s perception.

When manufacturers report noise levels, it is essential to specify the distance at which the measurement is taken. Noise levels decrease with distance. Typically, the distance of 10 meters is used.

The EN 17645:2022 standard mandates sound power level testing for heat pumps under 41 kW (outdoor temperature at 15°C and water temperature at 26°C). These tests must be carried out following the EN 12102-2:2019 standard for procedures and methods such as EN ISO 9614-1:2009 or EN ISO 3741:2010.

For Inverter heat pumps, tests are performed under minimum and maximum operating conditions.

 

Logo du Centre de Transfert de Technologie du Mans

The very low noise levels of POLYTROPIC’s Inverter swimming pool heat pumps are also validated by the independent French laboratory ALMACOUSTIC, a “Center of Expertise in Acoustics and Vibration” (formerly the CCTM, Technology Transfer Center of Le Mans).

Thanks to its recognized expertise in industrial acoustics and specific methodologies, ALMACOUSTIC has supported POLYTROPIC in qualifying its Inverter heat pumps.

 

Conclusion

  • Ensure that any COP or SCOP values are accompanied by the reference standard used, namely EN 17 645 for swimming pool heat pumps. Without this, the values have no legitimacy. Very high COP or SCOP values should raise concerns—check the conditions and standards used.

  • Prioritize a manufacturer that tests all its products under real-world conditions and provides certified data from independent laboratories under the European standards outlined above.

  • If certain information is not provided or seems disconnected from actual performance, it is pertinent to question and put it into perspective.

For any questions or clarification requests, feel free to contact one of our experts.