For Usage Display on Heat Allocation Meters
(Evaporation / Summer Display / Placement Disadvantage)
The heating regulations (HeizkV) have defined which devices and measuring systems may be used for the heating and warm water cost settlements since 1981.
The best value for money solution are the heat allocation meters. The audit and allowance of heat allocation meters are today covered by the norms of DIN EN 834 and DIN EN 835. Heat allocation meters are not measuring devices, they simply serve the purposes of splitting heating costs accrued. Critical for these devices is not „measurement exactness“ but „allocation exactness“. The values ascertained from the individual radiators are composed in relation to the sum of all values ascertained in the property. The read values say nothing about the amount of heating costs to be expected, as the usage is ascertained in physical measuring units. The alternative to heat allocation meters are the heat quantity meters, they are more expensive to buy and to maintain and are for many buildings uneconomic. Even with heat quantity meters, measurement errors are allowed within certain limits. The costs for an absolutely exact measurement would be so high, the whole usage measurement would be uneconomic.
Should a heat allocation meter show a small usage although a radiator is „turned off“, could be for many reasons: The frost protection safety on the thermostats starts the radiators off if room temperatures are low. When airing a room or when a radiator is close to a window, the start off temperature could be reached through the cold air entering the room. This results in heating that goes unnoticed. Also heat sources being placed too closely to radiators (washing machine, oven, electric heaters, etc) or sun rays can heat the radiators to over 32oC.
Following a warm summer, it is often requested that the units are reduced. The argument against this is that a) the units measured due to summer warmth cannot be ascertained and b) the request will not lead to any change in the heating cost fractions. If a display is increased due to summer warmth, all flats are basically affected. Because the costs to be split do not change, an increased or decreased quantity of total units will lead to the price per unit being lower or higher. Calculation corrections therefore will not lead to a change in the individual costs.
The only thing to be considered, are the units for summer evaporation. It does not suffice if a tenant carries out a reading in the flat. Readings must be taken before and after summer in all flats and it must be ensured that the heating cannot spring on. It should be considered, that usage display without heating use will not increase the heating costs to be allocated, but the two additional readings will increase the settlement costs. In our opinion this way is uneconomic and not wise. Furthermore, the values read on a heat allocation meter according to the evaporation principal are not to be utilised due to the short reading intervals and the statistical evaporation and scale that is set up for the reading periods of the previous year.
The different heat allocation meters use different methods against the problem of usage display without actually heating:
A. Heat Allocation Meters According to the Evaporation Principle
These heat allocation meters work according to the principle that a certain measuring fluid evaporates when influenced by heat. The fact that measuring fluid could also evaporate when radiators are turned off, because of the room temperature, cannot be eliminated. In order to balance the so called „cold evaporation“ (evaporation of measuring fluid without the radiator emitting heat 4.13 DIN EN 835) over the year, the ampoules for the heat allocation meters are „over filled“ according to 5.4 DIN EN 835. The quantity allowance of the so called cold evaporation is statistically ascertained and standardised according to the average climate. The decision about the necessary quantity follows with the audit.
B. Electronic Heat Allocation Meters
The electronic heat allocation meters work with different programming that eliminate measuring values under certain conditions. However, as of a certain radiator surface temperature (approx. 32oC) a measuring value is definite. This is necessary to, for example, avoid manipulation of the usage data collection of the heat allocation meter through heat accumulation. The switch on threshold is, according to 5.3 EN 834, a condition for the approval of heat allocation meters. Should a small registration happen once this threshold has been reached, it should be considered, that the heat allocation meters have such a large dissolution, that the value of one unit is relatively low. The E107 orientates itself within the 32oC area: a slow increase of temperature speaks for foreign heat, so that no registration follows, as where a fast increase of temperatures presumes that the heating is on and registration follows. The EHKV 1851 (one sensor device with start sensor) and the E112 (two sensor device) consider the temperature of the area up to 32oC. Registration only happens when a minimum difference between radiator surface temperature and the room temperature exists.
This is why the argument of flats in disadvantageous positions is often used. Since the heating cost regulations have been valid, a „correction“ of the usage values in favour of these flats is no longer allowed. The so called reduction process that took place through the construction of a special scale, is not justifiable either physically or measurement technically and contradicts the purposes of usage dependent settlements (Lammel, heat cost regulations, 2nd edition 2004, § 6 Rdn. 51 and the following pages; Dr. G Peruzzo, heating cost settlement according to usage, 5th edition 1996, page 53 onwards). According to § 7 part 1 heat cost regulations, it is only possible to consider warmth demand differences due to position of flats, with a suitable percent of the usage dependant costs to be split. In well insulated buildings with a low heat demand, an incentive for saving energy can be given by using high percent fractions. In buildings where the heating system is also used for warm water, the recommended split is 50% to 50%.
