FAQs

The amount of evaporation from a swimming pool is primarily governed by the difference in vapor pressure between the water and the surrounding air. Vapor pressure refers to the tendency of molecules in the liquid (in this case, water) to escape into the air as a gas. When the water’s vapor pressure is higher than that of the air, evaporation occurs as water molecules move into the atmosphere. Therefore, the greater the difference in vapor pressure between the pool water and the surrounding air, the higher the evaporation rate.

Several factors influence this difference in vapor pressure, including the temperature and humidity of the air, as well as the water temperature. A warmer pool will naturally have a higher vapor pressure, which encourages more evaporation, particularly if the surrounding air is cooler and drier. On the other hand, humid air can reduce the rate of evaporation, as the air already contains a high level of moisture, limiting its capacity to absorb more water vapor.

Air movement above the pool also plays a significant role in evaporation. Increased airflow, such as from ventilation systems or fans, can help to move the humid air away from the pool surface, reducing the humidity around the water and promoting more evaporation. In contrast, stagnant air tends to trap moisture near the pool, decreasing evaporation but creating a more humid environment in the pool hall.

The level of activity in the pool is another important factor. A pool with higher occupancy will experience a greater rate of evaporation due to the increased surface disturbance caused by swimmers moving through the water. More movement results in a larger exposed surface area, which accelerates evaporation. Additionally, swimmers often generate heat, which can increase the water temperature slightly, further increasing the evaporation rate.

In summary, the amount of evaporation from a swimming pool is influenced by the temperature and humidity of the air, the movement of the air, and the level of activity in the pool. Understanding these factors helps in effectively managing indoor pool environments, controlling humidity, and reducing energy costs associated with ventilation and dehumidification systems.

No, this is actually a myth. Condensation occurs when air comes into contact with a surface that is colder than the dew point of the air. The dew point is a critical factor and is determined by both the temperature and the humidity of the air. It’s important to understand that the relationship between air temperature, humidity, and surface temperature is what truly governs condensation, not simply keeping the air temperature slightly higher than the pool water temperature.

In fact, you can have the air temperature 5°C lower than the pool water temperature and still avoid condensation, as long as the dew point of the air remains below the temperature of the internal surfaces of the pool hall. This is where a well-designed ventilation system, such as the Recotherm unit, plays a key role in managing both temperature and humidity to maintain an environment where condensation is prevented.

For example, if the external temperature is -1°C and the room temperature is 30°C with a humidity level of 50%, condensation can still be avoided on surfaces like double-glazed panels. Similarly, if the air temperature is 25°C, a humidity level of 55% will be sufficient to prevent condensation on these surfaces.

Recotherm units are specifically designed to control both internal humidity and temperature, ensuring that the dew point stays within a range that prevents condensation, regardless of the air or pool water temperature. By carefully balancing these factors, Recotherm systems maintain a stable, comfortable environment while preventing moisture buildup on surfaces, ensuring the longevity of the building structure and creating a more pleasant atmosphere for pool users.

While heat pump dehumidifiers are a popular choice for many spaces, they are not necessarily the best solution for controlling condensation in a swimming pool environment. A heat pump dehumidifier is simply a different type of system that works by recirculating the air within the pool hall and removing moisture through a direct expansion evaporator. The heat generated during this dehumidification process is then used to heat the air and, in some cases, the pool water. 

However, there are significant downsides to using a heat pump dehumidifier for pool environments. One of the main concerns is that the dehumidification process is typically powered by electricity, which is often expensive to run. This can result in high energy costs, especially when the system operates continuously to maintain comfortable humidity levels in a large pool hall. 

Another issue with heat pump dehumidifiers is that they work by recirculating the air within the room, meaning they don’t address important air quality issues like removing chlorine fumes or body odor smells. In a pool hall, this can lead to a poor atmosphere that feels stuffy, uncomfortable, and less hygienic for swimmers. The inability to replace stale air with fresh air can create a less pleasant and less healthy environment for everyone in the space. 

In contrast, Recotherm ventilation systems provide a far superior solution. Recotherm units rely on fresh air intake to manage both humidity and air quality in the pool hall, which helps to remove harmful contaminants like chloramines (the byproduct of chlorine reacting with organic materials) and odors. By continuously introducing fresh air, Recotherm systems ensure better air quality and a more pleasant atmosphere for swimmers. 

Moreover, Recotherm systems are designed with energy efficiency in mind, utilizing advanced heat recovery technology to minimize the need for external heating. This not only keeps energy costs lower but also helps maintain a comfortable environment with minimal running costs. Recotherm units effectively control both temperature and humidity, ensuring that condensation is prevented while also creating a healthier and more comfortable environment for everyone in the pool hall. 

In summary, while heat pump dehumidifiers can be effective in some settings, they are not the ideal choice for swimming pool environments. Recotherm units offer superior air quality, greater energy efficiency, and better overall control of temperature and humidity, all while creating a more pleasant and sustainable atmosphere. 

Yes, using a heat pump as your heating source does affect the selection of the ventilation unit and its design. Heat pumps operate differently from traditional heating systems like gas or oil boilers, which means certain adjustments and compromises need to be made to ensure efficient operation while keeping costs manageable.

When heating is supplied by a standard boiler, the system is typically designed for a worst-case scenario: full fresh air intake and maximum heating demand for an uncovered pool during mid-winter. This design assumes high flow and return water temperatures (65°C/45°C), which are easily achievable with gas or oil boilers. With heat pumps, however, the situation is different due to their lower flow and return temperatures and their limited capacity to handle peak heating loads.

To accommodate this, the system design needs to adjust in the following ways:

Limited Fresh Air Operation in Winter In winter, fresh air has a much lower moisture content, meaning that less fresh
air is needed to achieve the same dehumidification. With a heat pump system, the unit may lose the ability to operate on full fresh air during cold months to avoid overloading the heat pump. This compromise reduces the overall heating
demand while still maintaining effective dehumidification.

Larger Unit Size and Heat Exchanger Adjustments Because heat pumps operate at lower water temperatures, achieving the required air temperatures can be more challenging. Often, a larger ventilation unit is necessary to handle these limitations. Even with a larger heat exchanger inside the unit, other factors such as airflow resistance and fan capacity may restrict performance. The design must strike a balance between increasing the unit size and maintaining feasible energy use.

Extended Heat-Up Times and Reduced Peak Performance Heat pump systems often require longer periods to heat the pool hall and may struggle to maintain the desired room temperature in the depths of winter. This is due to closer design margins necessitated by the heat pump’s lower temperature capabilities. While the pool hall may remain comfortable, achieving and maintaining very high temperatures consistently might not always be
possible.

All these considerations are aimed at optimizing the heat pump’s duty and reducing the overall equipment and operating costs. Heat pump systems can still be effective and energy-efficient for pool environments, but
the design must account for their unique limitations.

If clients or heat pump providers expect guarantees for performance in high-temperature environments, they may need to prepare for higher duties and increased costs. Recotherm works to strike a practical balance, designing systems that meet the needs of both customers and energy providers without excessive capital costs. Maintaining a room at 30°C with a 45°C coil temperature is a challenge, but Recotherm strives to deliver solutions that are both effective and cost-efficient.

While Recotherm specializes in designing and manufacturing high-end swimming pool ventilation units, we do not supply pool water heat exchangers. However, through our extensive work with pool contractors, we’ve observed that homes heated by air or ground source heat pumps are becoming increasingly common. This trend will only grow as new regulations after 2025 prohibit the installation of fossil-fueled boilers in new homes.

When sizing a pool water heat exchanger for a system using a heat pump, there are critical considerations that differ significantly from those of traditional boilers. The primary challenge arises from the way heat exchangers are sized based on supplier catalogues.

Most catalogues provide charts that list the required kW rating for the heat exchanger based on specific water volumes and three primary flow temperatures. However, these charts often overlook a vital question: How quickly does the pool water need to be heated?

The heat required to maintain a pool’s operating temperature is minimal compared to the energy needed to heat the pool water from a cold fill to its target temperature. Heat exchangers are typically sized based on the initial heat-up load, which can lead to oversizing, especially when dealing with heat pumps. Pool contractors generally aim for a heating rate of no more than 0.5°C per hour, meaning a 20°C increase (from 10°C to 30°C) would take approximately 40 hours. Some manufacturer charts assume a heat-up period of around 46 hours.

With a standard boiler, oversizing a heat exchanger has minimal financial impact since the cost difference for a slightly larger boiler is relatively small. However, for heat pump systems, oversizing the heat exchanger can lead to significantly higher upfront costs because the heat pump itself must also be oversized to meet the increased demand. The cost difference for a larger heat pump can be substantial, running into thousands of pounds.

To optimize efficiency and cost, it’s essential to consider longer heat-up periods. For example, increasing the heat-up time from 46 hours to 96 hours (4 days) could reduce the required heat exchanger size to 48% of the original, allowing the heat pump to be sized much closer to its actual operating load. This adjustment significantly reduces capital costs without compromising long-term efficiency.

We raise this issue because pool contractors often size heat exchangers directly from manufacturers’ charts without fully accounting for the heat-up time or the actual operating conditions of the heat pump. While these charts are designed for convenience, they don’t address the specific needs of systems using heat pumps. The first step in correctly sizing a heat exchanger should always be to calculate the actual heat demand, followed by selecting an appropriate heat exchanger based on the heat pump’s flow temperature and the desired heating time frame.

By carefully considering these factors, you can avoid unnecessary expenses while ensuring your heat pump system operates efficiently and effectively for your pool.

No, a three-phase electrical supply is not always necessary. Recotherm offers single-phase units capable of handling airflows of up to 1m³/s, which is sufficient for a domestic pool with an area of up to 100m². This makes our single-phase units an excellent choice for most residential applications, as they are designed to provide efficient performance without requiring a more complex or costly three-phase electrical setup.

However, for larger commercial pools or pool halls with higher demands, a three-phase supply may be necessary due to the increased capacity requirements of larger ventilation units. If your pool exceeds the size or operational needs of a typical domestic pool, we can advise you on the most suitable system to ensure energy efficiency and reliable performance.

Our range of units is designed to cater to both single-phase and three-phase installations, ensuring we can provide a solution that aligns with your electrical setup and pool requirements. Whether your pool is small or large, we’ll work with you to select a unit that fits your specific needs

Yes, Recotherm ventilation units can be designed for external installation by incorporating weatherproofing features to ensure they operate reliably in outdoor conditions. These weatherproof units are built to withstand exposure to the elements, including rain, wind, and temperature fluctuations, making them a practical option when indoor space is limited or when external installation is more convenient for your pool hall design.

However, there are a few considerations to keep in mind. While the unit itself can be weatherproofed, the display panel, which provides access to controls and system information, must be protected. To address this, the display panel can either be installed inside the building where it is easily accessible or housed in a dedicated weatherproof enclosure if it needs to be located outside. This ensures that the controls remain functional and protected from moisture, dust, and temperature extremes.

By offering the option for external installation, Recotherm systems provide flexibility to accommodate various building layouts and space constraints, all while maintaining the performance and durability that Recotherm is known for. Whether installed indoors or outdoors, the unit will deliver the same high level of efficiency, air quality, and humidity control for your swimming pool environment.

Yes, the display panel can be installed remotely, up to 800 meters away from the ventilation unit, providing flexibility in its placement. The panel is connected to the unit via a multi-core cable, which ensures reliable communication between the two components regardless of the distance.

This feature allows the display panel to be conveniently located in an area that is easily accessible to operators, such as a plant room, maintenance area, or office, even if the unit itself is installed in a less accessible location like an outdoor space or a separate building. By separating the panel from the unit, you can ensure that system monitoring and adjustments are simple and hassle-free, without needing to access the physical unit directly.

Recotherm’s design flexibility in allowing remote placement of the display panel ensures that their systems can be seamlessly integrated into a variety of layouts and configurations, offering convenience and functionality tailored to your specific needs.

Yes, the Recotherm unit has the capability to monitor and control the temperature of your pool water. This functionality is integrated into the system’s internal controller, making it a convenient and efficient solution for maintaining your desired pool water temperature.

To enable this feature, you will need a temperature sensor and a control valve. Both components are available from Recotherm and can be seamlessly integrated into your ventilation unit. The temperature sensor measures the current water temperature, while the control valve adjusts the heating system to ensure the pool water remains at your preferred setting.

By using the Recotherm system to manage your pool water temperature, you gain precise control, reducing the need for separate systems and ensuring that the pool environment remains comfortable and energy-efficient. This integrated approach simplifies operation and ensures that both air and water temperatures are balanced for optimal performance.

Yes, every Recotherm unit is supplied with a comprehensive control system, designed to manage all aspects of its operation effectively. The controls are fully integrated into the unit, providing seamless functionality for maintaining the ideal temperature, humidity, and air quality in your pool hall.

These controls are pre-programmed and ready to use, ensuring the unit operates efficiently right from installation. They include advanced features to monitor and adjust settings automatically, optimizing energy usage while protecting the pool environment and building structure.

Additionally, if you require customization, such as remote access or integration with existing building management systems (BMS), Recotherm can accommodate these needs to provide a tailored solution. Our controls are designed to make operating your unit as easy and intuitive as possible, delivering both reliability and convenience.

No, in most cases, the ventilation unit can be served by the same boiler that heats the pool water. Pool boilers are typically sized to handle the significant heating load required to bring the pool water from cold to a comfortable temperature of 30 °C within a specified time frame, such as 48 or 72 hours. Once the pool water reaches and maintains this temperature, the boiler generally has spare capacity that can be utilized to supply the ventilation unit.

For domestic installations, this shared arrangement is usually sufficient, as the boiler can efficiently handle both the pool water and the ventilation unit’s heating needs without additional equipment. However, for commercial projects, where larger pools or higher operational demands are common, additional considerations may be required. For instance, if the system must account for frequent backwashing or high rates of water turnover, extra boiler capacity may be necessary to ensure adequate performance.

Recotherm units are designed to work efficiently with your existing heating infrastructure, but during the design phase, it is essential to assess the total heating requirements to determine whether the existing boiler capacity is sufficient or if supplementary equipment may be needed.

The supply air in a pool hall should be distributed through either metal ductwork or builder’s work ductwork. It is essential to direct the air over the coldest surfaces in the room, which typically means the windows. Properly distributing the air in this way prevents condensation from forming on these surfaces. If there are other surfaces colder than the windows, this indicates a structural or insulation issue that should be addressed to maintain optimal conditions.

The return air, on the other hand, can be extracted from a single point on one of the walls. It is important to note that the location of the return air grille does not influence the distribution of the supply air, as supply and return operate independently in this context.

Additionally, care should be taken to avoid directing the supply air stream directly at the surface of the pool water. Blowing air across the water can significantly increase evaporation rates, leading to higher humidity levels and increased heating demands. Moreover, this can create an uncomfortable environment for pool users by making them feel colder due to the accelerated evaporation of water from their skin.

Proper design and placement of air distribution systems are critical for maintaining a comfortable and energy-efficient pool hall environment while ensuring the building structure is protected from moisture-related damage.

Yes, having a spa pool will impact the selection of the ventilation unit. Spa pools typically operate at higher water temperatures than standard swimming pools and are more active when in use, generating significantly more evaporation and humidity. This higher level of evaporation increases the demand on the ventilation system to manage the additional moisture in the air effectively.

To ensure the correct unit is chosen, it is crucial to inform the supplier or installer that you have a spa pool and provide details about its size. The unit’s capacity must be calculated to accommodate both the swimming pool and the spa pool,
factoring in the higher evaporation rates and specific conditions associated with spa usage.

A properly selected
Recotherm ventilation unit will handle the combined needs of your pool and spa,
maintaining a comfortable and safe environment while minimizing the risk of
condensation and protecting the building structure from potential moisture-related
damage.

Yes, it is possible to avoid condensation even if you cannot run ductwork directly to your windows. In such cases, specialist air distribution grilles can be used to ensure the air is effectively circulated throughout the pool hall and directed towards all corners of the room, including the windows. These grilles are designed to create a sufficient air throw, ensuring the movement of warm, dry air reaches critical areas where condensation is most likely to occur.

However, since the windows will not be directly covered by warm, dry air, you may need to operate the ventilation system at a lower indoor humidity level. Reducing the humidity ensures that the dew point of the air remains below the surface temperature of the windows, minimizing the risk of condensation forming.

Recotherm ventilation systems can be tailored to suit these conditions, offering precise control of temperature and humidity to maintain a comfortable and condensation-free environment, even in challenging situations where ductwork cannot be installed as traditionally recommended.

Yes, some of our smaller units, including the Aeris range up to 100, can operate from a standard 13-amp supply, making them suitable for domestic installations where only a single-phase power source is available.

However, larger units typically require a higher electrical capacity and will need a larger supply to accommodate their power requirements. This is especially true for commercial or larger residential pools where the unit’s airflow and heating demands are greater.

Recotherm units are designed to work efficiently within the
specified power requirements, and our team can advise you on the best unit for your pool and electrical setup. If a larger unit is necessary, you may need to consult an electrician to ensure your supply is adequate.

Yes, it is important to have the unit running 24 hours a day to ensure the building’s structure is protected from the high humidity levels that naturally occur in indoor pool environments. The continuous operation of the unit helps maintain proper ventilation, preventing condensation, mold growth, and potential damage caused by moisture build-up, which could deteriorate the building’s structure over time.

However, if your pool hall is well-insulated and you use a pool cover when the pool is not in use, the system can adjust its operation to become more energy-efficient. In these conditions, the unit will reduce its speed and power usage to the minimum necessary to maintain adequate airflow and prevent excess humidity. This means that while the system will still be running, it will consume significantly less energy, using only a small amount of electricity to power the return fan.

So, while the unit needs to operate continuously, you won’t need to worry about excessive energy consumption if the pool hall is properly insulated and covered. The system is designed to automatically adjust to the conditions, ensuring effective humidity control without unnecessary energy use.

Yes, to maintain the pool water temperature and prevent excessive heat loss, it is essential to keep the pool at the desired temperature 24 hours a day. The consistent warmth helps to reduce the risk of condensation, which can damage both the pool area and the building structure due to high humidity levels. Maintaining a stable temperature also ensures that the pool is always ready for use, avoiding fluctuations in comfort and water quality.

In order to do this, it is necessary for the hot water from the boiler to be available on demand at all times. The boiler must be capable of maintaining the pool’s temperature around the clock, especially during colder months when heat loss tends to be higher. While the boiler doesn’t need to be running at full capacity continuously, it must be able to respond quickly to maintain the required temperature whenever needed.

By keeping the system running consistently, the temperature of the pool remains stable, reducing the likelihood of energy inefficiencies and preserving the integrity of both the pool environment and the surrounding structure. This ensures that your pool stays in optimal condition while avoiding costly repairs or damage caused by moisture build-up.