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Heating optimisation in practice

In existing buildings, it is not unusual to find “high temperature heating systems”, as well as building envelopes which are either poorly insulated, or are without any insulation at all. The design of the distribution systems and heat circulation pumps is often inadequate, the flow values of the thermostatic valves used are many times too high, and hydraulic compensation is installed in less than 10 % of the systems. Only around half of the thermostatic valves can be pre-set at all.

In order to set the heating system in the best possible way, three steps must be taken: hydraulic compensation on the radiators by restricting the water quantity on the thermostatic valve housing or lockshield valves, the installation of electronically controlled pumps and their correct triggering, and setting the supply temperature on the central controller. These measures can result in a 70 – 90 % reduction in power consumption by the pump. Additionally, it is only through hydraulic compensation that the requirement is met for using the heat of combustion, the savings potential of which can be up to 11 % with condensing boilers which are already in operation.

In new buildings, hydraulic compensation is in effect obligatory, although in the EnEV German Energy Saving Ordinance of 2014, it will be expressly required. The KfW bank and the German Federal Office of Economics and Export Control require it at least within the scope of their support programmes for existing and new buildings.

The Optimus research project, which is supported by Deutsche Bundesstiftung Umwelt, has inspected the heating systems in 92 residential buildings – single and multiple family homes of different building age classes. With almost all the systems, the control could be better adapted to the system and the supply temperature could be reduced. The pump output could also be reduced in many cases. In order to record the large amount of data needed for the purpose, a personal visit to each heated room on site was required. For this reason also, automated methods for system optimisation could be an option in the future for large buildings with a complex heat supply system. However, the amount of time and effort required to create the model and for the technical realisation in relation to “normal standard” heating optimisation on site should be taken into consideration. Automated methods also need to be simpler and standardised. Only then can acceptable use-cost ratios be achieved.

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Addresses

Project coordination, method development
Fraunhofer ISE

Data recording and measurement, realisation in demonstration buildings
PLENUM Ingenieurgesellschaft

Development of hardware and software
ennovatis Schweiz AG

Development of building commissioning methods
HAW Hamburg

Scientific consultation on modelling and control technology
Energieagentur Regio Freiburg GmbH

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