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.
heat is supplied by a common central heating system or by a common district heating connection. A complete grouping of consumer units is called an account unit.
It could be necessary to divide an account unit into user groups, if an account unit comprises consumer units with typical differences (e.g. technically different types of heating systems, or different by way of consumption, e.g. industrial plants as opposed to private apartments).
Heat cost allocators only allow the determination of the heat consumption of each radiator in a consumer unit as a share of the total heat consumption of the account unit or user group (see clause 3). It is therefore necessary to determine this total heat consumption either by measuring the consumed fuel quantity or the amount of heat delivered (the latter e.g. by a heat meter).
The condition for correct use of heat cost allocators in accordance with this standard is that they are used in a heating system which:
— at the time of installation of the heat cost allocators, corresponds to the state of the art, and
— is operated in accordance with the state of the art (see Annex A, A.1).
Heat cost allocators in accordance with this standard shall not be used for heating systems where the temperature limits are exceeded. where the rating factor for the thermal power, K, is not clearly specified or where the heating surface is inaccessible. This applies e.g. to following heating systems:
flap-controlled radiators; radiators with ventilators; fan-assisted air heaters; bath-tub convectors;
heating systems where the radiators attached thereto are operated by steam; and horizontal single pipe heating systems exceeding more than one consumer unit.
3 Functional principle
Heat cost allocators in accordance with this standard are measuring devices for the registration of the temperature integral with respect to time. The temperature is the basis for the determination of the thermal output of the radiators on which the heat cost allocators are installed. Heat cost allocators in accordance with this standard, without electrical power supply based on the evaporation principle, use, of the characteristic temperatures determining the thermal output, only the temperature of the radiator surface (or the temperature of the radiator surface (or the temperature of the heat medium). The non-rated displayed reading is the approximate value of the time integral of the measured characteristic temperature of the radiator. This type of construction utilizes the so-called single-sensor method.
The rated displayed reading is obtained from the non-rated displayed reading by multiplication by rating factors, particularly with those for the nominal thermal Iower of the radiator and those for the thermal contact between the surface and the heat cost allocators (see 4.15). The rated displayed reading is obtained either by reading the heat cost allocators equipped with a product scale directly (see 4.11) or by later conversion of the non-rated displayed reading (see 4.12). The rated displayed reading is an approximation of the heat emitted from the heating surface over the measuring period and consumed by the user.
Thus the rated displayed reading is a measuring result influenced by characteristics of the heat cost allocators, of the radiator, of additional conditions and by factors of uncertainty of the rating factors and the installation. Consequently the measuring deviations (measuring errors) of the recorded heat consumption are not only dependent on the heat cost allocator alone. Thus, heat cost allocators cannot be calibrated in the same way as heat meters.
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 ainpoule will be exchanged against a full new one.EN 835-1994 pdf download.

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