Cost savings through permanent magnet technology

A local customer of the municipal drinking water supply in Germany operates several drinking water wells. The Franklin Electric Service team recently assisted in the installation and modernisation of a new pump system in a 40 metre deep well.

The pump system is positioned at a depth of approx. 25 metres and now includes a complete system consisting of a permanent magnet motor (PM motor), submersible pump and Variable Frequency Drive (VFD).

The municipal water supplier still had an unused permanent magnet motor from 2016 in storage. This was inspected and carefully serviced by the Franklin Electric Service team. After cleaning, the seals were replaced and the motor was ready for operation again.

The motor was paired with a submersible pump and supplemented with a cooling jacket. This separate cooling jacket is sealed above the pump inlet. The water is sucked in from below and channelled past the motor in order to dissipate the heat generated by the motor (convection) and generate sufficient cooling.

Firstly, the old motor-pump unit was lifted out of the well. The existing motor had been in use for more than 10 years and was now replaced by the 6-inch permanent magnet motor from Franklin Electric.

More than motors - Optimisation of the system with Variable Frequency Drive and PT100 temperature sensor

When operating a PM motor, a Variable Frequency Drive is essential. This not only allows the pump system to be utilised and controlled more efficiently, but also helps save energy and significantly extends the system's service life.

Previously, the system could only be switched on or off, which often resulted in an excessive water flow that had to be manually regulated using sliders. The motor was consistently operating at full load.

Now with a Variable Frequency Drive, precise control of the system’s requirements is possible. Individual parameters such as constant water pressure, flow rate, and level control can be conveniently selected and adjusted via the display.

The system also offers robust protection against various sources of interference, including short circuits, underload, overload, overheating, undervoltage, overvoltage, phase failure, phase imbalance, overpressure, and sensor errors.

Additionally, a PT100 sensor has been integrated into the submersible motor. Installed in the upper end shield, this sensor measures the temperature above the winding head and continuously monitors the winding temperature.

When the unit was lowered into the deep well, the leads of the motor and the PT100 were tightened opposite each other to avoid interference. Franklin Electric's PT100 temperature sensor is equipped with a 4-wire shielded cable, available in multiple lengths, which provides additional protection against high frequency interference that can occur in applications with Variable Frequency Drive.

Reverse Osmosis in Pharmaceutical Water Systems

Reverse osmosis (RO) is the premier filtration technique widely used in pharmaceutical water systems for its effectiveness in removing particles and contaminants. Utilizing a semi-permeable membrane, the RO system allows water to pass while retaining impurities. The process requires a driving force, applied as pressure via pumps, to propel water through the membrane.

In this system, an EV pump introduces water into a series of membranes, functioning as filters to separate the liquid into two streams: the ‘permeate’ (purified water) and the ‘retentate’ (waste liquid). To optimize efficiency and conserve resources, the retentate can be recirculated through another pump, minimizing energy consumption and material usage.

Advantages of Reverse Osmosis:

• Comprehensive removal of contaminants, including dissolved substances and minerals.

• Physical filtration without phase change, preserving energy and maintaining room temperature.

• Least energy-intensive among water treatment methods, relying solely on water pressure.

Meeting the Technical Demands of High-Pressure RO Systems

Given the high technical demands of RO systems, components must adhere to the highest standards of performance, materials, and flexibility. Franklin Electric’s Vertical Multistage Pumps are exemplary in this regard. The Stainless Steel construction offers exceptional resistance and reliability, minimizing downtime due to component replacement. Their superior performance and broad range of flow rates (up to 115 m³/h for the EV series) ensure precise pressure modulation to meet system requirements.

Franklin Electric offers a specialized High-Pressure system incorporating two vertical multistage pumps mounted in series, constructed from full AISI316 Stainless Steel with Victaulic pipe connections. This innovative setup allows Franklin Electric to achieve extremely high pressure that a single pump cannot match, due to the reinforced construction of the second pump, featuring a high-thickness casing and balanced mechanical seal. Victaulic collars enable the system to withstand pressures up to 50 bar.
A horizontal multistage pump (EH) is included on the same skid to recirculate retentate water, enhancing filtration efficiency and preventing water wastage. This configuration ensures optimal filtration performance, making the most of available resources.

The Ideal Choice for Water Purification

Franklin Electric’s dual Vertical Multistage in series pumps provide a robust, reliable solution for reverse osmosis systems, ensuring high-pressure delivery and efficient filtration. The combination of superior materials, advanced design, and energy-saving recirculation makes these pumps the ideal choice for pharmaceutical and other water purification applications.

Wide range of applications and cost savings

The Franklin Electric team recently supported an agricultural business to organise its irrigation system cost-effectively and precisely to its needs. Several well pumping systems were installed in wells 20-30 metres deep.

The project had several requirements for the desired well system:

• The system had to be suitable for various applications, as the fields are irrigated partly with sprinkler cannons and partly with drip hoses. The methods and areas vary constantly and are heavily dependent on the weather and season. The system therefore had to be designed for a wide range of applications in terms of operating points.
• A further focus was on cost savings for the economic optimisation of the operation. Enormous cost savings can be achieved by using the High Efficiency System.
• The customer also wanted a flexible system with multi-range motors that are suitable for all well systems. This allows him to flexibly swap the motor and pump between the wells as required.

Several well pump systems were installed, consisting of permanent magnet motors in the power range of 13-22 kW, VS submersible pumps (VS65/10) made of 304SS, corresponding cabling and a temperature sensor.

The system was supplemented by the perfectly matched DrivE-Tech COMPACT frequency converter with du/dt filter for motor protection. This is quick and easy to install via a mobile app and even enables remote control, real-time monitoring of system performance and remote troubleshooting by Franklin Electric's support team.

High-efficiency borehole systems engineered for excellence and sustainability

In all industries and markets, energy consumption is becoming a decisive criterion when selecting new systems and modernising existing ones. It is also becoming one of the most important aspects when pumping water from boreholes or tanks, in addition to the optimum dimensioning, reliability and quality of the system. As the energy consumption of a pump system accounts for up to 90 % of the total life cycle costs, the overall operating costs can be significantly reduced.

With its innovative High Efficiency System (HES), Franklin Electric is setting new standards in the industry. The system enables energy savings of up to 21 %. As a technology pioneer, Franklin Electric has been supplying the submersible pump market with highly efficient permanent magnet synchronous motors since 2017. The high-efficiency borehole pump systems (HES) achieve outstanding levels of efficiency, particularly as a complete package including all components. Several thousand installed units have so far proven this outstanding practicality and show up to double-digit energy savings as well as significantly improved efficiencies.

The key factor in energy savings and high efficiency is the motor's permanent magnet technology. Instead of a short-circuit induction motor, the high-efficiency motor incorporates a permanent magnet rotor design with buried magnets, which provides significantly improved efficiency and and overall lower energy consumption compared to a standard induction motor. The permanent magnet motor design eliminates electrical rotor losses, resulting in lower motor currents, improved partial load behavior and reduced temperature heat rise.

Franklin Electric proves that technological progress and ecological responsibility can go hand in hand. With the High Efficiency System, the company offers a forward-looking solution for water pumping that is both economical and environmentally friendly.

In Italy, three well systems were equipped with permanent magnet motors to achieve long-term energy savings. 

For two pivot irrigation systems, G.N. Tecnopompe from Castel Mella / Lombardy Italy installed three pumping systems with permanent magnet motors. The pump systems feed pivot irrigation systems which were set up to reduce water consumption as much as possible in order to counteract the climatic and structural problems related to energy and water consumption. Especially in Italy, the importance of this issue is constantly growing. Therefore, it was all the more important for the customer to focus on energy efficiency and sustainability also in the selection of the pumping system.

In addition to drilling the three wells, G.N. Tecnopompe also took care of the complete installation and setup of the system.

To create an energy-efficient, sustainable solution, the decision was made to use Franklin Electric permanent magnet motors, which are characterised by very high efficiencies.

By using Franklin Electric‘s 37 kW permanent magnet motors in combination with powerful pumps, savings of at least 7 kW can be achieved at full power.

It quickly became apparent that high savings could be achieved when using a coordinated system with permanent magnet motor and frequency converter.

Both the energy consumption and the water consumption could be reduced considerably. Due to the savings achieved, a considerable part of the investment can already be amortised in the procurement year.

Applications at a glance:

• Franklin Electric 6" Permanent magnet motor
• submersible pump
• DrivE-Tech Variable Frequency converter

Energy savings through permanent magnet technology

In all industrial sectors and markets, energy consumption is becoming a decisive criterion when selecting new systems and modernising existing ones. When pumping water from boreholes or tanks, this is also becoming one of the most important aspects along with optimal dimensioning and the reliability and quality of the system. Since the energy consumption of a pump system accounts for up to 90 % of the total life cycle costs, the operating costs can be reduced considerably.

Franklin Electric has developed the High Efficiency Pump System, which enables energy savings of up to 21 %. The key factor for energy savings and superior efficiency is the permanent magnet technology of the motor. Instead of a short-circuit induction type rotor, the high efficiency motor contains a permanent magnet rotor design with buried magnets with significantly improved efficiency and overall lower energy consumption compared to a standard induction motor. The Permanent Magnet Motor design eliminates electrical rotor losses resulting in lower motor amps, improved partial load behavior and reduced temperature heat rise.

Franklin Electric offers permanent magnet motors in a package with ideally matched components to further optimise efficiency and energy savings. This so-called High Efficiency System includes the PM motor, a submersible pump, a frequency converter and additional components such as a suitable output filter and, if necessary, a flow switch.

Numerous installations worldwide impressively demonstrate the success of this system, where great savings could be achieved. In most cases, the system pays for itself in less than 2 years.

Solar-powered drinking water supply

On Mount Athos in the Agio Oros region of north-eastern Greece, a new 4" High efficiency solar pumping system of Franklin Electric supplies an Orthodox monastic community with drinking water from a well. The particular challenge was that the area has no connection to the electricity grid. It was therefore decided to use a solar application to pump the necessary water from the 50-metre-deep well.

Fluida Pumps and pump equipment from Bulgaria took on this project and explored the possibilities. Looking for the best efficiency at a flow rate of 2 to 5 m³/h, they quickly decided on the High Efficiency pumping system of Franklin Electric. As the area has no connection to the electricity grid, a solar application had to be installed. A system with 10 solar modules was installed for this purpose.

4" High Efficiency Solar pumping system

• 4" submersible pump VS 4/14
• 4" permanent magnet PM motor 1.1 kW / 220V / 100 Hz / 4000N
• Solar Variable Frequency converter DrivE-Tech MINI Solar 2.011 MP

Another difficulty with the installation was that the area also has no internet access. So it was not possible to control and set up the system remotely. All data was coordinated in advance with the Franklin Electric support team so that the installation could take place smoothly on site.

Coordination with the customer was also difficult, because the monk was only available once a day at 6 a.m. to clarify open questions. Today, the well produces water reliably and supplies the monks with water every day.

Voltage boost and reduction of solar modules

Solar applications are about converting sunlight into electricity. The most important value is the so-called solar radiation (measured in W/m²). This number tells you how much energy you can get from the actual sunlight. The solar radiation depends on your location and changes with the time of day, with the weather conditions and also during the year. Each day you only have a certain window of time where you have enough sunlight to keep your system running at full speed. So the solar system must be carefully sized to achieve the desired system performance. In addition to solar irradiance, this will depend heavily on the number of solar panels and how well your solar drive controls motor and pump. The MVPT algorithm of the High Efficiency system maximizes system performance.

So, when operating a pump with solar energy, it is important to generate sufficient electrical power, but even more important is sufficient voltage. The pump speed and thus the system performance is determined by the electrical voltage. To generate enough voltage, you need to connect enough solar panels in series. This will generate the voltage level needed to operate at full speed.

But if weather conditions change, the voltage can drop, causing the system to immediately reduce pump speed to keep running. This reduces the amount of water pumped, but not just linearly. Due to pump affinity laws, the pump head or pressure is reduced squared, which then leads to a further reduction in water flow as you run at a different pump operating point.

So, if you haven’t sized your system carefully, or if you’re using low efficiency components, you run the risk of running in what’s called a dead head situation. The pump is still operating, but it’s not generating enough head to overcome a certain level, and the result is that water flow stops. With the lower energy consumption of the High Efficiency System, you have an additional safety reserve that allows you to pump more water, or longer.

Franklin Electric has further enhanced this feature on its smaller 4” systems by adding a solar frequency inverter to provide an advanced voltage boost function. This voltage boost feature makes it possible to size your system based on power rather than voltage, saving you up to 50% on solar panels compared to a standard system without the voltage boost feature. The bottom line is that you need fewer solar modules, which reduces the initial investment and installation cost, and you also save on solar module mounting.

A Franklin Electric FNC Close-coupled End suction Centrifugal pump with extended shaft supplies water to the fountains in the Hilden municipal park.

FNC End suction pump

The well maintenance department of BPK Brunnen- und Pumpen-Service GmbH in Moers/Germany replaced a standard centrifugal pump that supplies water to three fountains in the Hilden town pond.

When it came to selecting the right pump, the decision was made in favour of the powerful FNC 80-160/110 pump with 11 kW, which achieves flow rates of up to 156 m³/h (50 Hz) and heads of up to 28 m (50 Hz). In addition to the required performance parameters, criteria such as high quality and durability and corrosion resistance were also decisive in the selection of the pump.

Another fountain in the Hilden city park is currently being equipped with a submersible pump from Franklin Electric, which achieves a delivery rate of up to 144 m³/h and a delivery head of up to 578 m.

The renovation of the fountains was part of an inner city project that also included the upgrading of the centrally located city park with its pond. The fountains of the water body does not only look beautiful and please visitors, but  also is important for the circulation and aeration of the water body.

Read more about the application in the attached case study.

The Seaman’s Fountain of Bardolino in Italy is working again after two years, thanks to the Franklin Electric pump system, consisting of a 6" pump with a 6" encapsulated motor.

Pressure boosting for water games

The musical fountain of Bardolino on the shores of Lake Garda, designed in 2001, was finally back to bubble again after two years of standstill, thanks to a visual and technical redesign by a local company. The new system consists of a 6" pump system from Franklin Electric, which was provided by the company Idroagrifer in Pastrengo (VR). Idroagrifer is a Franklin Electric distributor of borehole systems in the Veneto and Trentino Alto Adige area.

In this type of ornamental fountain, the pump system pushes the water through jet nozzles. This increases the pressure and the fountains reach the desired height.

The 6" systems from Franklin Electric consist of a 6" encapsulated submersible motor and a 6" Stainless steel submersible pump, which are characterised by high reliability and durability.

Reliability and robustness

Franklin Electric‘s submersible motors allow power ratings up to 45 kW and are equipped with hermetically sealed windings. This anti-tracking system provides mechanical support, isolates the winding in the stator and ensures rapid heat dissipation.
The motors are equipped with the SandFighter® sealing system with SiC/SiC mechanical seal and sand protection as standard. The hydrodynamic liquid-lubricated radial bearings and heavy-duty Kingsbury type thrust bearing also ensure 100% maintenance-free operation.

The 6" submersible pumps of the VS series are made of Stainless steel and guarantee a long service life. Thanks to the proven components, this pump can withstand the toughest environments. It is suitable for flow rates up to 80 m³/h. The maximum permissible sand quantity for this series of submersible pumps is 100 g/m³.

The water installation is dedicated to Saint Alberti, a navy engine mechanic who went on board the submarine Topazio during the Second World War, which did not return to base in 1943 after a war mission.
 
Today, the sprinkler fountain, whose play of lights is reminiscent of the Italian colours, delights both tourists and locals walking along one of the most famous shores of Lake Garda. And thanks to the durable Franklin Electric integrated products, it will continue to do so for many years to come.

For more information about the products, please refer to the product sites or the attached pdf.

Approx. 30 multistage pumps of the EH (horizontal) and EV (vertical) series have been installed in various irrigation systems in Veneto (Italy) for pressure delivery in the distribution of water-fertiliser mixtures in distribution channels.

Requirements for irrigation systems constantly increasing

In cooperation with Irrigazione Gastaldelli, who organises the installation of irrigation systems, Franklin Electric
supplied about 30 multistage pumps to 10 local agri-food companies in Rovigo, Verona, Padua and Ferrara. Both for fruit growing (pears and blueberries) and for vegetable cultivation in greenhouses and in the ground, the ideal
suitability of Franklin Electric’s pump systems was demonstrated.

Fertiliser irrigation technology is becoming increasingly common in agriculture as it maximises the management of raw materials such as water and water-soluble fertilisers, and reduces the risks associated with water shortages. Advanced technologies can optimise the fertiliser irrigation process enormously. However, this requires high precision in dosing and scheduling of the system to distribute the necessary nutrients to the plants in a targeted manner.

The advantages of fertiliser irrigation lie in the reduced manpower requirements due to the automated processes,
in the reduced impact on the soil due to tillage without use of agricultural equipments and in the better distribution of the fertiliser. In addition, there are fewer scattering losses with nutrient-water solutions, as drip irrigation precisely targets the root of the plant. However, this technique also has disadvantages, as it can only be used for irrigated crops and it is always necessary to use a technologically advanced and therefore often expensive system compared to traditional methods.

Avoidance of corrosion, unnecessary repairs and downtime

Because the technical demands on the irrigation systems (greenhouse or ground) are high, all parts of the system
must meet the highest quality standards in terms of performance, materials and flexibility.
For this reason, Franklin Electric‘s multistage pumps are the first choice for these systems. The Stainless steel construction ensures good resistance to the highly corrosive fertilisers and long-term reliability, avoiding unnecessary system downtime due to component replacement.

The excellent performances and the wide range of flow rates, up to 29 m³/h for the horizontal EH series and up to
115 m³/h for the vertical EV series, allow pressure modulation to meet the requirements of any system. Appropriate water pressure is needed to ensure the necessary mixing of water and fertiliser, and thus the supply and growth of the plants.
Franklin Electric‘s multistage pumps can ensure this high pressure and thus distribute the perfectly composed solution with micro-sprinklers in the right amount over the entire extent of the plant. This guarantees each seedling the necessary nutrient supply.

Flexibility for all needs

The pressure booster pumps must transport the water-fertiliser solution from the tanks into the system. The space
available to place the pumps and the distances that have to be covered when transporting the liquid to the plant
vary greatly. Franklin Electric therefore offers a wide range of pumps to provide the optimum solution for each application. The horizontal multistage pumps make it possible to save space at height, while the vertical multistage pumps are suitable for applications with little usable installation space.

In addition, Franklin Electric offers a wide range of accessories, from pressure vessels to shut-off valves and special designs such as self-priming horizontal pumps or vertical high-pressure pumps connected in series.
Last but not least, the DrivE-Tech and Drive-Tech MINI frequency converters optimise the operation of the pumps
through state-of-the-art electronic technology.

For more information about the products, please refer to the product sites or the attached pdf.

The historic Thruxton race track located in the south of the UK has been equipped with new water boosting sets powered by Franklin Electric, high quality pumps and smart controls offer a reliable solution with efficiencies in mind.

Increased requirements on pressure and flow

As the Thruxton racecourse site has grown over the years, the owners found that the water system struggled to maintain required flow and pressure.

Henry Gill of HG Water was therefore approached to design a new booster system for the historic racecourse‘s water supply that could keep up with the increased water demand.

The complete water booster packages were supplied by KGN Pillinger, a British water booster manufacturer. Richard Sharp (Business Development Manager) says that when it came to selecting the components, it was quickly clear that Franklin Electric‘s E-Tech product would be chosen, as the quality and competitive price of the Franklin Electric installation allowed KGN to build high quality equipment within the customer‘s budget.

Booster systems supply the racetrack

The installation is based on a booster set made by two vertical multistage EV10 pumps, each one equipped with DrivE-Tech 2.030 frequency converters, coupled in parallel via manifolds, shut-off valves and check valves. The DrivE-Tech frequency converters modulate the operating frequency in order to maintain a constant set value.

The system is complemented by an EH Dtm multistage horizontal pump, consisting of an EH 5/5T6 pump and the DrivE-Tech MINI integrated frequency converter.

Overall, the project includes new storage tanks, kiosks and booster pumps, as well as the variable-speed controls to feed the different areas of the site. The old piping was re-routed to the new kiosks, and thanks to the additional storage tank, sufficient water can now be distributed even during peak periods.

> The vertical multistage pumps from Franklin Electric offer high levels of efficiencies within a robust design and when used with the DrivE-Tech variable speed controls the increased demands can now be met. <  (Henry Gill of HG Water)

For more information about the products, please refer to the product sites or the attached pdf.

With the right components, the efficiency of a heating system with well installation can be increased and energy costs sustainably reduced. Geoquip Water Solutions in the UK recommends the combination with the High Efficiency System from Franklin Electric.

The increasing demand for renewable energies is causing the increasing numbers of geothermal heating systems in both the commercial and private sectors. Savings of up to 80 % compared to conventional fossil fuels and the reduction of CO2 emissions are among the advantages. In addition, there are various possibilities of financial subsidies from the legislators.

In addition to systems with geothermal probes and geothermal collectors, there is the option of operating a heating system with a well system. The two wells, the so-called suction and absorption wells, transport groundwater to the surface and use the heat of the groundwater as an energy supplier for water-water heat pumps, which extract the heat from the groundwater to heat rooms and process and drinking water in the house.

Since groundwater is an important resource for plants and living organisms, it must be recirculated. The pump in the suction well pumps the groundwater to the surface. After the thermal energy has been recovered in the heat exchanger, the now colder water is pumped back into the ground water via the absorption well. When positioning the two wells, it is important to consider the flow direction of the groundwater.

Immense savings potential through the right borehole pump

With geothermal heating systems, special care must be taken at the planning stage, because the potential savings over the lifetime of such a system are immense if the system is correctly dimensioned from the outset. The cost of purchasing and installing a typical geothermal heat pump system in an average house in the UK is around 14,000 to 19,000 pounds. A multiple of this costs the energy that is invested over the entire life of the system. It is therefore worthwhile to design the system ideally in order to achieve the maximum benefit.

The first thing to do is to make sure that the most efficient geothermal heat pump is used for operation, which also applies to the extraction pump in an open-loop system. This may sound obvious, but it makes no sense to have a „green“ geothermal heating system if the source pump is working around the clock and consuming far more electricity than necessary to move the water in the loop.

Therefore, the selection of the right components in particular is crucial. In an open-circuit system, the borehole pump is an important component of this. If the right pump for the job is not chosen here, the system cannot run effectively.

Permanent magnet technology as the key to outstanding efficiency

The key factor in these energy savings is the efficiency of the motor‘s permanent magnet technology. Instead of a short-circuit induction rotor, Franklin Electric uses a permanent magnet rotor design with integrated magnets. The total electrical rotor losses of a motor are eliminated, resulting in a significant improvement in efficiency. In addition, the PM motor has lower heat generation and requires less current to run at the same pump load. A frequency converter is required to operate a PM motor.

Remote control via App

The system is available in the sizes 4" 6", 8" and 10". Included are a submersible motor, a submersible pump, a frequency converter and the matching output filter.

The 4" system also offers the ability to remotely control and monitor system performance in real time using an App. Franklin Electric‘s support team can also access the system in this way to assist with problems or setting new parameters.

For Geoquip Water Solutions, the HES is the most energy-efficient solution

Mike Deed, Managing Director of Geoquip Water Solutions, has more than 30 years’ experience in the water treatment and solutions sector. He works with strategic partners to ensure customers receive the maximum benefit from their investment. He believes that the most energy efficient solution on the market is the High Efficiency Borehole System (HES), designed and manufactured by Franklin Electric.

» Here, Franklin Electric has set new standards in energy efficiency, because unlike most systems on the market, this system is not equipped with an - usually less energy-efficient - asynchronous motor, but uses an asynchronous NEMA standard permanent magnet motor, which has achieved motor energy savings of up to 21 % compared to standard asynchronous motors in numerous installations worldwide.«

The HES selection and sizing tool provided on the Franklin Electric website helps to select the right system. This tool can also be used to compare energy savings based on runtime and current energy prices. Systems typically pay for themselves within the first two years.

As with all things, being armed with the right information and components makes a difference. Given the long-term benefits that can be achieved through geothermal systems, it is definitely worth investing in the best.

This is how the thermal heat is obtained

The water-to-water heat pump transfers the thermal energy to a special refrigerant. This is initially liquid and evaporates when it absorbs the thermal energy. It then flows through a scroll compressor, which in turn increases the pressure and temperature of the medium. In the process, the steam is passed through two interlocking spirals. As one of the spirals moves eccentrically in circles, several gas spaces are created between the spirals, which become smaller and smaller towards the inside of the component, thus causing the pressure to rise. In the middle of the scroll compressor, the gases are finally pressed into the connected pipe. Here, the transported energy is transferred to the heating water. The refrigerant vapour cools down and liquefies again.

The efficiency of the system depends on the temperature difference between the design temperature of the heating system and the temperature of the environmental heat source. The groundwater is about 10 °C all year round. The compressor therefore does not have to use as much energy to raise the temperature, which makes the system very energy efficient.