Heat meter

a heat meter (HKV) is equipment for the consumption-dependent computation of heating costs. It is not a measuring instrument, but collection equipment, because it - differently than z. B. a heat counter - no physical dimension measures, but only dimensionless units (lines). Only by relationship calculation of the collection results several homogeneous heat meters can in the account of heating costs the individual heating costs of the individual users be determined.

Although in Germany physical dimension with ungeeichten and/or. not calibratable measuring instruments in principle not to be measured, can heat meters may be used after the heating costs regulation for the collection of individual heating energy consumption.

Table of contents


of the heat meters consists usually of a back, mostly of metal, which are connected heat conducting with the heating element, and a front part, which are attached and verplombt to the back . The front part mostly is from plastic and contains the measuring device.

operational principle

by the heating up of the heating element warms up also the back. The temperature gradient is integrated over the heating season (one year according to heating costs regulation ) and forms so the measured value. Since the delivered amount of heat depends also on the size and design of the heating element and on the heat transfer between heating elements and heat meters, the measured value of each heating element is multiplied by an individual factor.

This can take place either in the account of heating costs, one speaks then of a unit scale, because each heat meter is equipped with the same scale, or already by means of the heat meter. In this case the heat meter is equipped with a so-called product scale, which already considers the factor. With electronic heat meters one reaches this effect by a programming. The determination of the quality factor takes place in the context of the assembly of the heat meter. In addition the manufacturer and type of the heating element - as far as possible - are determined and an air passage is taken. The computation of the factor is a trade secret of the respective heat measuring service and presupposes exact knowledge of the assigned heat meter and the heating element, which are won in extensive measuring and test series.

Beside the unit or product scale some heat meters have an additional control scale. This is divided differently and serves to determine reading errors.


the heat meters are divided after their function mode into two large groups: Heat meter according to the evaporation principle and electronic heat meter. The heat meters are displaced according to the evaporation principle ever more by the electronic heat meters by the market.

heat meter according to the evaporation principle

with the heat meter according to the evaporation principle rests an open above glass tube filled with a liquid against the back. Depending upon temperature the measuring liquid evaporates faster or more slowly. The quantity of the liquid evaporated forms the measured value. On the front part of the heat meter a scale is attached, with which one can read off the measured value by a window.

When measuring liquid are suitable liquids, which evaporate so slowly that the supply in the heat meter is sufficient also at high heating element temperature for one year reliably, z. B. Methylbenzoat or 1-Hexanol. The measuring liquid evaporates in small measure also at ambient temperature, if the heating element is cold, approximately in the summer. To reconciliation for this so-called cold evaporation the measuring tube is filled beyond the zero point of the scale.

Capillary heat meter
during the annual main reading is replaced the tube by a again filled. With some devices the tube can be also locked and be kept to the preservation of evidence in the heat meter a further year. A comparison between previous year and current year is however not possible thereby because it concerns not physical units and arises the price for each unit only in the case of the account of heating costs. For better distinction the measuring liquid will provide in each year with another coloring material.

The suitability of these devices is disputed. Larger Fehlmesungen can develop, if the cold evaporation is different to substantial extent in the individual dwellings. This is for example the case if a dwelling has a particularly large sun exposure in the summer (attic dwelling with many and large windows) or if warmth is delivered still from other sources than the heating. At modern low temperature temperatures, those according to the principle of the calorific value technology function are evaporation tubes no longer permissible.

capillary heat meter

is very small the diameter of the tube (capillary), then speaks one of the capillary heat meter. Capillary heat meters need less from that human toxicological disputed measuring liquid and are enough because of their longer scale and the smaller reading error, which arise with conventional Verdunstern by Kapillaraszension, of their accuracy to electronic heat meters near, are however more inexpensive than these.

electronic heat meters

elektronischer Heizkostenverteiler
of electronic heat meters

with the electronic heat meter the temperature of the heating element and the temperature of the room air are seized by two sensors. The temperature difference is integrated by an electronic arithmetic unit and indicated on a process card display or an electromechanical speedometer in the form of counting steps. With simpler heat meters the ambient temperature feeler can also be missing (project-suppl.-guesses/advises). In this case a constant ambient temperature is accepted. Also two-feeler equipment leaves with certain operating conditions, z. B. with manipulation attempts, the ambient temperature unconsidered.

Similarly the cold evaporation with the heat meter according to the evaporation principle it can come also with the electronic heat meter despite issued heating element to counting steps. The effect arises with high ambient temperature, z. B. at unusually high temperatures in the summer. This characteristic could be suppressed technically perfectly, results however from the defaults of the technical regulations (EN 834), which must be kept by the manufacturers, so that the collection devices become certified.

The power supply of the arithmetic unit takes place via a battery. With older devices this is exchanged during the annual main reading by the Ableser. Current devices (2004) contain a firmly inserted lithium battery, which can supply the heat meter up to ten years. Afterwards either the entire heat meter or the front part is exchanged, since also the other electronic construction units achieved their expected life span after this length of time.

With electronic heat meters some functions are possible, which are inconceivable according to the evaporation principle with heat meters:

  • Deadline reading: The heat meter stores to a deadline (z. B. 31.12.) the reading off and begins again with zero to count. The reading can take place at any time after the deadline. The reading remains stored to the preservation of evidence up to the next deadline.
  • Memory of the monthly values: The heat meter stores the reading of each monthly. Thus intermediate reading off are void with user change.
  • Read off by radio: The readings are transferred at the deadline by radio to a data collecting tank outside of the dwelling. The Ableser does not have to enter the dwelling any longer.
  • Check total formation: The heat meter computes a check total from various data, from which afterwards reading errors, disturbances or manipulation attempts are to be recognized.

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