INDUSTRY INSIGHT


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Why pipework specification matters more in the low-temperature era


Matt Densham, divisional director for building services at pipework specialist FRÄNKISCHE, explains how the growth of low-temperature heating systems is placing renewed focus on the types of pipework specified


T


he transition towards low-temperature heating is fundamentally changing the way heating systems need to be designed. As


the industry moves away from traditional gas boilers towards heat pumps and other low-carbon technologies, greater attention is being placed on system efficiency. In this transition, the pipework distributing the heat can be easily overlooked. For decades, pipework specification has been


a relatively straightforward exercise. Copper has traditionally been the benchmark for sizing, while installers have become increasingly familiar with plastic alternatives for applications where flexibility and ease of installation are priorities. However, when a system is operating at lower


flow temperatures, achieving the required heat output requires greater water flow. Consequently, the hydraulic performance of the system – including pipe sizing, internal bore and pressure losses – becomes increasingly important.


Lower temperatures, greater demands


Heat pumps can operate at higher flow temperatures, but their efficiency reduces as temperatures increase. Designing systems to operate effectively at lower flow temperatures is therefore critical to maximising their efficiency and achieving energy savings. Consequently, getting the whole system right is more important than ever. With a traditional boiler, there was often more


scope to compensate for shortcomings in system design by simply increasing the temperature. With a heat pump. If the distribution system cannot deliver the required flow rate efficiently, the performance of the system as a whole can be compromised. For installers and specifiers, this means pipework


can no longer be treated as an afterthought. Getting the sizing right from the outset is fundamental.


Why internal bore matters


This is where the choice of pipe material becomes important. The flexibility of plastic pipe makes it particularly attractive for modern installation methods, including runs beneath floors and between an external heat pump unit and the internal system. But plastic pipe generally has a thicker wall


than copper. As a result, two pipes with the same nominal external diameter can have significantly different internal bores. For example, a 28mm plastic pipe can have an internal bore around 13% smaller than an equivalent


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28mm copper pipe. That reduction is an important consideration when higher flow rates are required. It is therefore important that pipework is specified according to its actual hydraulic performance rather than simply relying on traditional nominal sizing.


Combining the benefits of plastic and metal


This is one area where multilayer composite pipe (MLCP) can offer an alternative. MLCP combines the flexibility and installation benefits associated with plastic pipe with the dimensional stability and hydraulic characteristics associated with metal. A 32mm MLCP pipe, for example, can provide an internal bore comparable with that of a 28mm copper pipe, while retaining the flexibility to be supplied in coils and installed in longer continuous runs. That makes it particularly suited to applications


where long flow and return runs are required, including pipework beneath floors or connecting external and internal heat pump units. There is also the internal surface of the pipe to


consider. MLCP can provide a smoother internal bore than copper, reducing pipe roughness and supporting improved flow characteristics. This becomes more relevant as systems are designed around lower temperatures and higher flow rates.


Beyond the initial installation


Pipework selection also needs to consider what happens after the system has been commissioned. Pipework installed beneath a floor or kitchen is not particularly easy to access if problems occur later. MLCP’s smooth internal surface can help reduce the potential for the build-up of deposits, while its flexibility enables long runs to be installed with fewer joints. For buried applications, manufacturers can also offer pre-insulated solutions, providing an additional layer of protection and helping to simplify


installation. The use of continuous runs is valuable for flow and return pipework, where reducing the number of connections can improve both installation efficiency and long-term reliability.


The right fit


It is also important not to consider the pipe in isolation. Every fitting and change of direction within a system has the potential to affect flow. For example, a tight, conventional elbow


creates greater resistance than a swept fitting. FRÄNKISCHE’s patented swept elbow has been designed to minimise this resistance, with testing demonstrating a flow-rate improvement of up to 55% compared with its knuckle-style elbow.


Education is the next challenge


The technology itself is not necessarily the barrier to greater adoption. One of the biggest challenges is awareness. Pipework for example may have received relatively little attention in the specification of heating systems historically because conventional boilers were more tolerant of variations in system design. That cannot necessarily be assumed with heat pumps. As the UK accelerates the transition towards


low-carbon heating, the industry needs to consider the system as a whole; from heat source through to heat emitter, and everything in between.


The next generation of heating


The scale of the heat pump transition makes this increasingly important. With the UK needing to dramatically increase the number of heat pumps installed in both new-build and retrofit applications, seemingly small specification decisions will be repeated across hundreds of thousands of systems. The transition to low-temperature heating


requires a change in mindset. The industry has spent decades designing around high-temperature boilers, where there was greater tolerance for inefficiencies within the distribution system.


A more holistic approach.


Pipework specification needs to move higher up the agenda. Correct sizing, adequate flow, low resistance and appropriate material selection are more than mere technical details; they are fundamental to ensuring the heating system performs as intended.


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