McDonald Engineers Issue Warning over RHI Programme

Monday, 02 June 2014

The confirmation of the government’s Renewable Heat Incentive (RHI) Programme being extended to include additional fuel sources has been highly anticipated, however one of the UK’s leading manufacturers of hot water systems has issued a warning over the potential dangers from the incorrect specification of hot water cylinders.

The new RHI Scheme is expected to create a surge in installations of renewable heat sources, such as solar thermal, air and ground source heat pumps and solid fuel.

Consequently, McDonald Engineers are urging all Installers and Specifiers to champion the benefits of selecting hot water cylinders made from Copper and avoid underperforming systems and importantly the potential issues of Legionella and microbial growth in lower temperature stored hot water.

McDonald Engineers have been at the forefront of developing hot water cylinders designed to harness renewable energy since the 1970s and their expertise is regularly called upon by architects, engineers, specifiers and installers to assist with specifications.

Copper remains McDonald Engineers’ main material of choice for hot water cylinders.  Copper has been used for many reasons and at the forefront is it’s durability, heat transfer properties and flexibility of manufacturing.  Many installers given the choice for their own home will always choose copper.

When you consider copper’s heat transfer is around 400W/mK, compared to Stainless Steel’s 20W/mK  and the ability to offer far more surface area in a copper cylinder than a stainless steel cylinder – copper can deliver significantly improved heat recovery times.

The result of this, is systems such as Solar Thermal and Heat Pumps will deliver what they are meant to – cost savings to the householder and a benefit to the environment.

Copper can also significantly reduce the threat of bacteria growth, such as E.coli and Legionella, which pose a larger threat in lower water temperatures which renewable energy applications can often be subject to.

Research shows that Legionella pneumophila will actively multiply in water at temperatures between 25‐45°C and its only when the temperature reaches 55°C that the bacteria will be killed off.

This becomes a key issue in renewable energy and in particular solar energy, where the water temperatures achieved can be less than traditional fuel sources.

While the heat transfer of copper coils is likely to maximise heat input, thankfully copper’s natural bacteria killing properties can dramatically reduce the risk of bacteria spreading. For example, in tests, it took 34 days for E. coli 0157 to die on stainless steel, 4 days on brass and just 4 hours on copper.

Now that the RHI scheme includes technologies such as heat pumps, biomass as well as solar thermal, McDonald Engineers are urging installers and specifiers to be fully aware of the potential performance and health issues which could cause significant problems in the future.

Jamie Stewart, McDonald Engineers’ Sales Director, commented "Making Copper hot water tanks your preferred choice for renewable energy installations will not only maximise the benefits of these technologies, by increasing efficiency and improving performance but ensure the water is stored in the best storage material available.”