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Introduction to hot water

Why do we have water heaters and why do we use water for space heating? We use hot water cylinders to limit the effect from the energy source and provide a more stable load. Water is the perfect energy carrier for distributing heat from a heat source to several rooms. With water as the energy carrier, any heat source, both high and low temperature, may be used. Hot water is also a perfect storage medium for the capture of renewable energy.

Hot water: When taking a shower, a normal flow rate is about 18 litres / minute, and the temperature 38-40 °C. If this water were to be heated directly during consumption, it could take up to 45 kW.


Should there be a need for simultaneous tapping, the effect could need to be around 90 kW. The supply of such high effects from the electric grid is not possible, and can only be met with oil / gas burners or by storing hot water in a cylinder. The storage method is widely used, since it only requires 3 kW effect, and provides stable load on the grid.

Space heating: A central space heating system consists of an energy source, a distribution system and products for delivering the heat to the room. When using water based distribution system and heat delivery system, one is free to use any energy source.


Both heat pumps, solar collectors, gas / electric boilers, biofuel / pellets are suitable alternatives. The heat delivery system can be implemented in floors, walls or roofs, or in radiators or fan convectors. Under floor heating has a large area for spreading the heat consistently in the room, and provides for unmatched comfort. It also provides the opportunity of reducing average indoor temperature by approximately 2 degrees, which saves energy. Whatever choice of heat delivery system, it is recommended to use low temperature delivery systems (max. 50 °C for the circulating water). This way, environmentally friendly heat sources such as heat pumps and solar collectors may be used directly without peak heating.

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