scope:

In connection with consumption billing, this standard applies to heating systems where, due to their design, substantial amounts of heat are given off by pipes to the consumer units to be heated but are not generally metered. This involves, in particular, vertical one-pipe heating systems with uninsulated rising pipes as well as horizontal one-pipe heating systems, such as those employing the Rietschel- Henneberg principle (uninsulated circular pipeline; see Bibliography). For this purpose, it is technically irrelevant whether such pipes are installed in an open manner or concealed in screed or walls. Concealed pipes, e.g., in screed or walls, can give off considerable amounts of heat that can exceed the heat supplied by open pipes due to the thermal coupling of the building structure. The heat output of pipes can have a considerable influence on the accuracy of heat cost allocation.

Cost allocation for the supply of hot water is not part of the scope of this standard.

This standard provides recommendations on reducing pipe heat loss and defines procedures with which pipe heat loss can be factored into heating cost billing, thus preventing or reducing cost distortions.

It is not the purpose of such procedures to compensate for deficiencies in installation engineering (e.g., excessive flow temperature or pump pressure, insufficient pipe insulation). Where technically feasible and economically meaningful, such deficiencies should be rectified in order to optimise operations. For details, refer to Section 7.1.

The consumption-based portion of the heating costs (generally, 50 % to 70 % under the German Heating Cost Ordinance (HeizkostenV)) depends on the units of the respective metering system. These are frequently heat cost allocators, which are affixed to radiators or heating elements. But there is also unmetered heat output by way of useful heat, particularly as a result of heating pipes with insufficient insulation or no insulation at all that run through heated rooms (pipe heat). Such unmetered heat energy causes cost shifts within the billing unit. Unmetered heating of individual rooms (e.g., common areas like staircases or drying rooms) has a similar effect.

Such cost shifts are characterised by the fact that users with an above-average consumption within the billing unit are burdened with a proportion of the consumption costs that is higher than the cost equivalent of the metered heat energy that they have consumed. Conversely, users with a belowaverage consumption are allocated a proportion of the costs that is too low. This effect can be aggravated by measures to modernise the building, particularly by measures to improve the energy efficiency of the building envelope (thermal insulation). Similar cost shifts that are not caused by pipe heat loss, but rather, for example, by high heat supply expenditure, are not part of the scope of this standard.

The purpose of the following procedures and methods is to offset or reduce these cost shifts that occur and that are deemed substantial under standard DIN EN 834. In particular, any individual added costs resulting from pipe heat shall be considered in connection with the corrective requirements. Where the maximum added cost of a billing unit is less than 10 %, the system does not require correction.

The procedures and methods shall be applied to the billing and allocation of consumption-based heating cost calculations for central hot water heating systems. They primarily concern one-pipe heating systems.

The method described in this standard can also be applied to groups of consumer units.