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Interface Units (HIU) with a plate heat exchanger, temperatures as low as 50˚C can safely be adopted. This is supported by research in combi boilers, which reveals homeowners often run their boilers at much lower temperatures. Operating at 50˚C also helps to ensure the minimum return temperature requirements of Part L for community heating (Domestic Building Services Compliance Guide, section 6) of less than 40°C for DHW and 50°C for radiator heating are met. Selecting HIUs with active return temperature control can further improve this. Refining design to help minimise network losses by reducing return temperatures means that older practices of producing DHW at higher temperatures are inappropriate for a heat network using HIUs, producing domestic hot water via plate heat exchangers. These perceived requirements for high temperatures are largely based on outdated and ineffective stored water systems. Experience in Denmark has shown that stored water adds to overall heat losses, whilst providing no benefit to the resilience of the network design. With confusion over which requirement takes precedence, opting for ACOP L8, with its lower temperature requirements, will ensure the most efficient system.
Insulation
Further reductions in heat losses can be achieved through effective pipe insulation. There is currently little specific guidance in this area aimed at heat networks and our recommendation would be to model the effects of insulation thickness against a whole life cost. As a guiding principle, it is essential that network losses are kept lower than 15 per cent and ideally below 10 per cent. This is another factor which will impact favourably on energy costs for final users. Overall when it comes to designing and installing heat networks, a fluid
approach is needed where the design is continually reviewed and refined, rather than remaining fixed. A tailored approach that brings together manufacturers, contractors and designers, with the needs of end-users at the forefront of consideration is essential to the success of a district heating system.
District heating
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www.aquatechpressmain.co.uk Head Office: 01206 215121 Manchester: 0161 226 4727
February 2018
Aquatech Pressmain is an AGM brand. 17
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