Find the right meter

Most consumers would agree that a heat cost allocator must measure accurately. But what does that actually mean and what can be expected of a quality meter? You can get closer to the answer by replying to four questions.

What you can expect of your meter - checklist

1. Is your meter intelligent?
2. Is the meter type-approved?
3. Is the meter suitable for the heating system?
4. Is the meter correctly installed?

If you lack information about the property’s heating system, you can find information in the property’s control manual.

1. Is your meter intelligent?

Many believe the purpose of radiator metering is to measure the heat emitted from a radiator, but unfortunately it is not quite that simple. Only heat originating from the central heating system should be measured. At first glance, this appears an easy and straightforward task: consumption is registered when the radiator temperature is higher than that of the surrounding air. However, radiators are able not only to emit heat, but also to absorb heat from the surroundings, for instance on a hot summer’s day when the sun is shining and heating up the radiator. The intelligent meter therefore needs to be able to establish whether the heat emitted from the radiator is due to the sun shining into the flat or the consumption of heating from the central system. How intelligent is your meter?

Brunata’s electronic heat cost allocator guarantees accurate measuring in all conditions, also when the radiator is hot due to sunshine or because the wood-burning stove is on.

2. Is the meter type-approved?

Today, most meters are type-approved. The type approvals are issued by the Danish Accreditation and Metrology Fund (DANAK) and approved meters must be clearly marked with a TS number. All heat cost allocators installed after 1 August 1998 must be approved according to DS/EN 834 and DS/EN 835.

Brunata’s heat cost allocators meet these requirements. Accordingly, they can be used in low temperature systems and in systems where the supply temperature is governed by the exterior temperature.

3. Is the meter suitable for the heating system?

In addition to being type-approved, heating meters installed in Denmark must also meet another important requirement: they must be suitable. The requirement is not new – it has existed for just over 50 years and is set down in the Rent Act. It means that the meter must be suitable for the heating system in which it is installed. In Denmark, this is usually a low temperature system. The purpose of the act is to ensure that meters are not used in conditions other than those for which they are approved. If, for instance, a meter is only approved for high temperature systems, it must not be installed in a low temperature system.

Changes to a property, such as post-construction insolation, can result in the meters suddenly becoming unsuitable. Assume a property is insulated post-construction, resulting in a much reduced heat loss. The property can now be heated with significantly lower radiator temperatures. The lower radiator temperature may cause problems for meters which start to register at a particular temperature, as the radiator temperature is now lower than the start temperature of the meter. In other words, the radiator may be on without consumption being registered.

4. Is the meter correctly installed?

A final important point is the meter’s installation location on the radiator. The radiator surface temperature drops from the water supply point to the return point and the choice of installation location is therefore crucial to correct consumption registration. However, this only applies if the radiator has a thermostat valve. The temperature drop is normally smaller on radiators without thermostat valve and the meter location is therefore less important.

The correct installation height has been established in laboratory tests with the various meter types. In 1999, a doctoral thesis about this very subject was published in Stuttgart. It establishes that electronic meters with two-sensor measuring should be installed at 65 per cent of the radiator’s build height. This is interesting, as many German meters in Denmark are installed at 75 per cent of the radiator’s build height, resulting in major measuring errors. The correct installation height is 2/3 up the radiator for electronic meters and 3/4 for evaporation meters.