Heat cost allocator
A heat cost allocator (HKV) is a device for the consumption-dependent calculation of heating costs . It is not a measuring device , but a recording device , because - unlike e.g. B. a heat meter - does not measure any amount of heat, but only supplies non-specific units that reflect the summation of the temperature (difference) over time. Heat consumption can only be derived from factors resulting from the type and size of the radiator. Ultimately, the individual heating costs of the individual users are determined by calculating the ratio of the recording results of several similar heating cost allocators in the heating cost billing .
The heat cost allocator usually consists of a back part, usually made of metal, which is connected to the radiator in a heat-conducting manner, and a front part, which is attached to the back part and sealed . The front part is usually made of plastic and contains the detection device.
The back section heats up as the radiator heats up. The temperature (or the temperature difference relative to room temperature at two electronic sensor devices) is on the heating period (one year according heating regulation) integrated and thus forms the measurement value . Since the amount of heat emitted also depends on the size and type of radiator and the heat transfer between the radiator and the heat cost allocator, the measured value of each radiator is multiplied by an individual factor.
This can be done in the heating bill. One then speaks of a single scale because every heat cost allocator is equipped with the same scale . If, on the other hand, the heat cost allocators on different radiators are equipped with different scales, so-called product scales, no conversion takes place because the factor has already been taken into account by the choice of scale. With electronic heat cost allocators, the scaling is achieved through programming. The assessment factor is determined when the heat cost allocator is installed. For this purpose, the manufacturer and type of the radiator - as far as possible - are determined and measurements are taken. This leads to the radiator performance as the first part of the evaluation factor. The factor is then corrected by the so-called Kc value, which describes the heat transfer between the heating medium, ultimately the radiator, and the heat cost allocator. The radiator evaluation requires the knowledge of precise data about the heat cost allocator used and the radiator, which are obtained in extensive series of measurements and tests.
In addition to the unit or product scale, some heat cost allocators have an additional control scale. This is divided differently and is used to identify reading errors.
The heat cost allocators are divided into two large groups according to how they work: heat cost allocators based on the evaporation principle and electronic heat cost allocators. The heat cost allocators based on the evaporation principle are increasingly being displaced from the market by the electronic heat cost allocators.
Heat cost allocator based on the evaporation principle
In the case of the heat cost allocator based on the evaporation principle, a small glass tube filled with a liquid rests on the back. Depending on the temperature, the measuring liquid evaporates faster or slower. The amount of evaporated liquid forms the measured value. On the front part of the heat cost allocator there is a scale with which the measured value can be read through a window.
Liquids that evaporate so slowly that the supply in the heat cost allocator will be sufficient for a year even at high radiator temperatures are suitable as measuring fluids. B. methyl benzoate or 1-hexanol . The measuring liquid evaporates to a small extent even at room temperature when the radiator is cold, for example in summer. To compensate for this so-called cold evaporation , the measuring tube is filled above the zero point of the scale. In rare cases, the cold evaporation can lead to incorrect measurements if they are caused by other heat sources in the individual apartments, e.g. B. Sun exposure, has great differences.
At the annual main reading, the tube is replaced with a newly filled one. With some devices, the tube can also be sealed and kept in the heat cost allocator for another year to preserve evidence. However, a comparison between the previous year and the current year is not possible because the units are not physical and the price per unit is only obtained when the heating bill is made. For better differentiation, the measuring liquid is given a different color every year.
For modern low-temperature heating systems with average design heating medium temperatures below 60 ° C, normal heat cost allocators based on the evaporation principle (class A according to EN 835) are not permitted, as their measurement accuracy is insufficient. This is particularly important if the building is subsequently insulated and equipped with a new boiler, because the original design temperature is then no longer reached.
Capillary heat cost allocator
If the diameter of the tube is very small ( capillary ), one speaks of a capillary heat cost allocator. Capillary heat cost allocators require less of the human toxicologically controversial measuring liquid and, due to their longer scale and the lower reading errors that occur with conventional evaporators due to capillary ascension, their accuracy can match electronic heat cost allocators, but they are cheaper than these. They mostly work with the measuring liquid 1-hexanol and are then approved for average design heating medium temperatures from 55 ° C and higher (class B according to EN 835).
Electronic heat cost allocators
With the electronic heat cost allocator, the temperature of the radiator and the temperature of the room air are each recorded by a sensor . The temperature difference is integrated by an electronic calculator and shown on an LC display or electromechanical counter in the form of counting steps. In the case of simpler heat cost allocators, the room temperature sensor can also be missing (single-sensor device). In this case a constant room temperature is assumed. A two-sensor device can also be used under certain operating conditions, e.g. B. in manipulation attempts, the room temperature is not taken into account.
Similar to cold evaporation with the heat cost allocator based on the evaporation principle, there can also be counting steps with the electronic heat cost allocator despite the radiator being displayed. The effect occurs at high ambient temperatures, e.g. B. at exceptionally high temperatures in summer. This property could be completely suppressed technically, but results from the specifications of the technical regulations (EN 834), which must be observed by the manufacturers so that the recording devices are approved.
The calculator is supplied with energy by a battery . With older devices, this is replaced by the reader during the annual main reading. Current devices (2004) contain a built-in lithium battery that can supply the heat cost allocator for up to ten years. Then either the entire heat cost allocator or the front part is replaced, since the other electronic components have also reached their expected service life after this period of time.
Electronic heat cost allocators offer additional functions compared to devices based on the evaporation principle:
- Date reading : The cost allocators stores to date (eg December 31st.) The reading (current consumption) under the old / previous year (M - Memory) and begins to count from zero again. The reading can take place at any time after the reference date. The reading remains stored for evidence until the next due date. On the next set day, the current consumption value is saved to the previous year's value (M memory) that has already been saved. In this way, the entire consumption is saved and you can track the exact consumption even if it was not possible to read off in a year (or several years). For this purpose, the last previous year's value read (M) is subtracted from the newly read previous year's value (M) and the difference results in the exact consumption between the last known reading and the new reading.
- Saving the monthly values : The heat cost allocator saves the reading for each month. This eliminates the need for intermediate readings when changing users.
- Reading by radio : The readings are transmitted by radio to one or more data collectors outside the apartment. The reader no longer has to enter the apartment. The due date values and mostly also all month-end values are sent a few times and saved in the data collector. This data can be read out on site or accessed by the measurement service via the Internet , GSM or UMTS .
- Checksum generation : The heat cost allocator calculates a checksum from various data , from which reading errors, malfunctions or attempts at manipulation can be recognized afterwards.
Although in Germany goods or consumption cannot be measured with non- calibrated or non- calibratable measuring devices, according to the heating cost ordinance , heat cost allocators may be used to record proportionate heat consumption . In accordance with Section 5 (1), sentences 2 and 3 of the Heating Costs Ordinance, the prerequisite is approval by an expert body. Authorized bodies are only those bodies whose suitability has been confirmed by the competent authority under state law in collaboration with the Physikalisch-Technische Bundesanstalt . A registration device is approved if it complies with the recognized rules of technology or if its suitability has been proven in another way.
- Norbert Eisenschmid, Franz-Georg Rips, Dietmar Wall: Operating Costs Comment , 2nd edition 2006, ISBN 978-3-8240-0912-1
- Kreuzberg / Vienna: Handbook of heating cost accounting : 6th edition. Werner Verlag 2005, ISBN 3-8041-5160-4 .
- Lammel: "Heizkostenverordnung (Commentary)" 3rd edition. CH Beck Verlag 2010 (with novella 2009), ISBN 978-3-406-59008-5
- Peruzzo: heating billing based on consumption . 5th edition Luchterhand Verlag 1996, ISBN 3-472-02503-4 .
- Pfeifer: The new heating cost ordinance (comment). 4th edition 2010, Haus & Grund Verlag and Service, Berlin, ISBN 978-3-939787-28-0 .