EN 835-1994 pdf download.Heat cost allocators for the determination of the consumption of room heating radiators Appliances without an electrical energy supply, based on the evaporation principle.
Because of the described characteristics the measuring result is not related to physical energy units. The rated displayed reading is non-dimensional. It is only a value relative to the sum of the rated displayed readings of the account unit or of the user group. A relative value of a measured rated displayed reading which has been defined in that way has to be understood as a part of the total heat, consumed by the account unit or of the user group. At the end of the measuring period, this value is established separately for every radiator. From the sum of all the rated displayed readings for the radiators of a consumer unit, the above relative value will determine the part of the heat consumption of the respective consumer unit related to the total consumption of the account unit or the user group.
Heat cost allocators consist of at least a casing, an ampoule with the measuring liquid, a reading scale, the installations and the seal. The seal serves to protect against unauthorized manipulation. Each heat cost allocator is a functional unit. Its individual parts are manufactured in compliance with certain tolerances. Thus each part of a particular kind of heat cost allocator (type, make) functions in the same way when used in the same way.
The measuring liquid in the open and transparent ampoule evaporates as a function of the temperature and the duration of the influence of that temperature. After each measuring period (normally 12 months) the old ampoule will be exchanged against a full new one.
4 Definitions
For the purpose of this standard, the following definitions apply.
4.1
reference condition
for the purpose of determining the rating factors and the c-value, a reference condition must be defined. The reference condition can be freely selected within certain limits
the reference condition of a radiator is as follows:
— upper flow inlet;
— mean heating medium temperature:
tm 50 °C to 65 °C;
— reference air temperature tL = (20 ± 2) °C. it shall he measured 0,75 in above the floor and at a distance of 1,5 m from the heating surface in a test chamber with a stable climate;
— heating medium flow (water flow through the radiator) at tV/tR/tL 90 °C170 °C/20 °C
where:
tv is the flow temperature;
tR is the return temperature:
4.2
reference temperature of the measuring liquid
the reference temperature of the measuring liquid is used for the determination of the rating factor K(. (see 4.16.2). The reference temperature is to be determined in the reference condition
4.3
design flow and return temperatures, mean design heating medium temperature, design temperature of the measuring liquid
the design flow and return temperatures are the temperatures of the heating medium of the radiators required to reach the design indoor temperature in the heated rooms under steady state conditions at a heat load corresponding to a geographically determined design reference outside temperature. The mean value of the design flow temperature t and the design return temperature tHJt is the mean design heating medium temperature This temperature is to be determined from the logarithmic mean value of the excess temperatures relating to the reference air temperature of 20 °C. The temperature of the measuring liquid under these conditions is the design temperature of the measuring liquid tFI
4.4
displayed reading
the displayed reading is the reduction of the liquid level in scale graduations, measured from zero on the scale. The displayed reading may he unrated or it can directly represent the rated displayed reading (see 4.5). Interpolation is permissible
4.5
rated displayed reading
the rated displayed reading is the displayed reading rated with the rating factors in accordance with 4.16
4.6
nominal evaporation
the nominal evaporation is the displayed reading (see 4.4 and 4.5) after 210 days at a measuring liquid temperature of 50 °C
4.7
evaporation rate
the evaporation rate v is the rate of the change of the liquid level.EN 835-1994 pdf download.

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