Operating Instructions

Siemens Building Technologies LUM4-SITS-GB0-KCWDB 06.02.2013 5/ 34
Task of the Kc values database
Heat cost allocators are used for the recording of the heat output of radiators and the consumption
related allocation of the heating costs to the individual consumers of a usage unit.
In accordance with DIN EN 834, heat cost allocators are:
“Recording meters for the temperature integrated over time. The temperature is used to determine the
heat output of the room heating surfaces at which the heat cost allocators or their sensors are
installed.”
“The consumption value is an approximate value for the heat provided by the heating surface and
used by the user during the measuring time. The consumption value will be read directly at the heat
cost allocator or it will be calculated by a later conversion of the non-evaluated display value.
Therefore, the consumption value is a measuring result that includes the characteristics of the meter,
the room heating surface, other boundary conditions as well as additional uncertainties of the
evaluation factors and the installation. Therefore, measurement deviations (measurement errors) do
not only depend on the meter. This means that heat cost allocators cannot be calibrated in the same
manner as heat counters.”
So-called evaluation factors are used to adapt the heat cost allocator to the different radiators (radiator
standard output, installation type and position). The evaluation factors are determined with great effort
in special test chambers. The DIN EN 834 standard describes the evaluation as follows:
“The evaluated display value with the designation consumption value is derived from the non-
evaluated display value by a multiplication with the evaluation factors, especially for the standard heat
output (KQ) of the room heating surface and for the heat contact (Kc) between the sensors and the
temperatures to be recorded."
"The evaluation factor Kc takes the different thermal connection of the temperature sensors to the
temperatures to be recorded on different types of radiator design into account."
Since the connection of the temperature sensors to the water in the radiator is strongly influenced by
the radiator's design shape, there are also different Kc values for different radiators.
The Kc value database is an easily understood interface to determine the Kc evaluation factors for the
use of a certain heat cost allocators in a property and to administer it for an entire property.