- Report #: NT VVS 127
- Approved: November 2001
This standard describes procedures and prerequisites for determining the heat output from floor heating systems in residential buildings, offices and other buildings put to similar uses. It describes the relationship between the operative temperature in the room and the mean floor temperature for different heat flow densities into the room. The maximum heat output to the room is limited by the permissible floor temperature.
The necessary heat flow density from the floor heating system is given by the design heat requirement for the building or for an individual room and by the floor area employed for heating, subject to the proviso that the permissible floor temperature is not exceeded. In turn, this enables the necessary mean temperature of the water circuit to be determined.
In the case of waterborne heating systems, the heat output is expressed as the heat flow density in relation to the mean differential temperature of the heating medium, which is the temperature difference between the operative temperature of the room and the logarithmic mean temperature of the water circuit.
The standard calculates downward heat losses which, when added to the heat output to the room, gives a total heat output from the water circuit. The necessary water flow can be calculated from a given temperature drop across the water circuit. In addition, the efficiency of the floor heating system, or the proportion of thermal power used for useful room heating, can be calculated
The standard offers alternative ways of determining the heat output from the floor heating system:
1. Calculation, in accordance with this standard.
2. Type testing, in accordance with this standard.
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