CIBSE publishes new guidance on LTHW heating systems

CIBSE, LTHW heating systems
The entire range of technologies that feature in modern LTHW heating systems for commercial buildings is covered in this new guide from CIBSE.

The last 20 years have seen significant changes on the technology of LTHW heating systems for commercial buildings — so new guidance from CIBSE will be very welcome.

Legislation has forced designers to improve the efficiency of their heating systems, so a designer now has far more options than before. The new CIBSE Application Manual 14 ‘Non-domestic hot water heating systems’ provides guidance on the design, installation and commissioning of water based heating systems.* It is CIBSE’s first new guide on this topic for 20 years.

Mike Campbell of AECOM, one of the main contributors to the new manual, explains, ‘AM 14 is an excellent point of reference for anyone involved in the design, installation, commissioning, testing and operating of low-temperature hot-water heating (LTHW) systems, that are installed in most buildings. It covers all boiler and burner types, including bio­mass, and also includes guidance on low/zero-carbon heat sources such as CHP, solar and heat pumps — indicating how to integrate them into heating systems.’

The guidance is aimed at both new and existing buildings, with separate sections covering the design require­ments for each type of project. As Mike Campbell says, ‘It covers design decision processes that can be employed for both new-build projects and refurbishment of older buildings in order to apply the optimum solution that best suits the building type, construction and usage. This could be use a mix of traditional technologies and renewable energy technologies, for example’.

But the guidance goes well beyond simply the design stage. Effective and efficient heating systems need more than good design, so AM14 considers the requirements from design right through into operation, and maintenance. Campbell explains the systems thinking behind the guidance.

‘In addition to providing design guidance, the applications manual also includes good practice advice on the installation, testing, commissioning, maintenance and trouble shooting of LTHW systems. A very useful part of the manual is the trouble-shooting section, where tables of common problems associated with the heat generator, flue, pumped circuit and controls that are encountered in reality are listed — together with possible causes of failure and suggested remedial actions.

This guide has been produced to address the most recent legislation and to account for the significant advances in technology that have occurred. A typical heat- ing system used to consist of non condensing boilers with constant volume pumps running a circuit of radiators operating with flow 82/71°C. Nowadays the generator may be a condensing boiler, heat pump, biomass boiler or CHP engine. The pumps are likely to be inverter-driven variable-speed pumps providing variable flows and controlled by 2-port valves on the heat emitters. The circuit may be weather compensated, BMS controlled, low-temperature circuit, and the heat emitters may be under-floor, active beams or radiant panels. This manual provides up to date guidance helping designers select the optimum solution.

As noted above, AM14 has separate chapters for new and existing building design. Upgrading, refurbishing or replacing heating systems in existing buildings, with all the physical constraints they impose, presents a much greater challenge than designing a new system for a new building. Not only does the engineer need a full understanding of the type of system installed previously, but also an understanding of the logic and intent behind its design at the time of installation. Only with this knowledge can reasonable decisions be made on upgrading. There are various types of heating systems currently installed in buildings. AM14 describes these so that existing systems undergoing refurbishment can be easily identified.


AM14 covers every component of a heating systems including the following:

•Heat sources
•Flow measurement and regulating devices
•Heat emitters
•Flue and chimney design
•Draught systems
•Combustion and ventilation air supply
•Fuel storage
•Water treatment
•Safety controls
•Electrical installation

As building-services engineers seek to reduce the energy use and carbon emissions of their projects, AM14 is an invaluable tool for those engaged on heating systems, from design right through the supply chain to installation and operation. It is illustrative of the increasing need to integrate the whole supply process, and to adopt a more systems based approach to services engineering. AM14 should be a welcome addition for all those involved in engineering heating systems.

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