Temperature level comfort heating compared to domestic hot water Heatcurve 90 °C Heatcurve 80 °C Heatcurve 70 °C Heatcurve 60 °C




Outside temperature Domestic hot water












at 65°C) will set the temperature demand for most of the year. Even with the 90°C-degree heat curve, only around 900 hours a year will require a supply temperature above 65 to provide comfort heating. The return temperature must be lowered In essence, the DH company in Viborg must deliver a supply temperature of 65°C for around 8,000 hours every year. Hence, finding ways to motivate consumers to lower the return tem- perature is interesting. The return temperature is set by the temperature level of the two heat demands. It is recommend- ed to have comfort heating in houses at around 21°C. The the- oretical return temperature is, therefore, close to this temper- ature. Typically, approximately five degrees higher is possible. So, a goal of 25°C from the comfort heating is not impossible to reach. Domestic hot water needs a circulation temperature of 50°C, so the return temperature from this is usually higher than from comfort heating. If there is no circulation, the do- mestic hot water can have a return temperature at the same temperature as comfort heating since the temperature on the cold side is the domestic cold water.

temperature possible with the best available technology, and then even a bit lower, as technology evolves and will allow for even lower supply temperature in the future. In Denmark, the DH companies supply heat to cover primarily heat for two different demands: Domestic hot water and the comfort heating of the building. During a year, one of the two heat demands sets the required supply temperature. The com- fort heating sets the temperature needed during the winter when the outside temperature is coldest. When the temper- ature outside rises above a certain level (around zero degrees Celsius), the domestic hot water demand starts to influence the required temperature level to deliver safe domestic hot water. The figure below shows the normal supply temperature at the consumer over a year in different building types. The dif- ferent heat curves show the supply temperature for comfort heating in different buildings, where the heating system has been dimensioned to different supply temperatures – mainly based on the energy efficiency of the building and the radiator system. Sometimes it is possible to divide the heat network into separate sections. In this case, it is possible to take advan- tage of the different demands for supply temperature in the design of the various heat network zones. As shown in the fig- ure, the demand for domestic hot water (supply temperature

The goal is to save money for the customers To motivate the consumers, there must be a goal for them in-

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