HVAC
The insulation performance of pre-insulated pipe manufactured specifically for district heating installations varies considerably and a pipe supplier should be able to advise on the most appropriate choice. This will depend on a range of criteria, including the energy source, the distance between the energy source and the end point user and the size of the network. Insulation performance will also impact on the cost of the installation, as pipe with lower thermal conductivity will be more expensive.
There are other ways to bring down the capex cost of the project, however. In addition to taking advice from the pre-insulated pipe supplier on configuration and optimised routing, specifiers should seek their advice on the diameter of pipe required. Each section of pipe has a flow and return pipe within the insulated casing and this should be sized to meet the anticipated demand from end user. Usually, there will be a ‘spine’ of larger diameter pipe leading to a network of smaller diameter pipe ‘branches’, and early engagement with the pre-insulated pipe specialist can help to avoid over-specification.
The pre-insulated pipe supplier can also advise on the most appropriate approach to installing pipe connections. For example, Uponor offers Wipex coupling connectors that offer a conventional approach to joining two sections of pipe by fitting over the join, or a Q&E (Quick and Easy) fitting, which is installed using a special expander tool, fitting securely inside the pipe. With training and use of the specialist tool, the Q&E fitting can reduce installation costs by speeding up installation.
Reflecting real usage patterns Historically, many district heating systems have failed to achieve their potential energy efficiency because the centralised plant has been oversized. This is because the calculations used to assess the energy output required have been based on maximum load requirements, rather than actual usage patterns. On a residential development, peak energy demand for
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hot water can be two or three times greater than the requirement for heating and, while all residents may switch their heating on at the same time during a cold snap, it’s unlikely they will all take a bath at the same time! Consequently, even if the maximum output of the energy source is 20% lower than the maximum demand (calculated using raw occupancy data) it may still only be required at 70-80% capacity at times of peak demand (calculated based on usage patterns).
Similarly, contemporary pipe systems like Uponor’s Ecoflex, do not allow calcium build up so the pipe bore should never be oversized when using a polyethylene- based pipe system as there will be no reduction in bore over time.
CASE STUDY Advantages in action
At Orchard Close in Watton, a cul-de-sac of 30 social housing flats owned by Flagship Group, a district heating system has been installed to replace outdated and inefficient Economy 7 heating.
Installed by renewable heating specialist, Finn Geotherm, the system uses two 60kW Lampoassa ground source heat pumps, linked to a 2400 litre thermal store, which qualified for RHI funding. Each flat then has its own HIU (heat interface unit) hot water radiator circuit and hot water tank.
Finn Geotherm specified Uponor’s pre-insulated Ecoflex Thermo pipe for the district heating system infrastructure, along with the company’s Q&E (Quick and Easy) pipe connectors. A total of 220 metres of Ecoflex was installed, with 50mm thermos twin dual pipe used to provide flow and return for the main spine and 32mm thermos twin dual core pipe used to create the localised connections to the properties.
www.uponor.co.uk. TOMORROW’S FM | 87
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