Versatility of Hot Water Cylinders to Harness Multiple Heat Sources

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McDonald Water Storage truly lived up to their ‘Hot Water Storage Solutions’ motto when manufacturing two bespoke cylinders for a project undertaken by VitoEnergy, highlighting the versatility of hot water cylinders to harness multiple heat sources.


A complete overhaul of a properties plant room was undertaken to enable multiple heat sources to be used, including an oil boiler, ground source heat pump, solar thermal and solar PV to not only provide the house with heating and domestic hot water, but to also heat the outdoor swimming pool. To maximise the input benefits and the space available, bespoke designed hot water cylinders were required.


To maximise the benefits from the available heat sources, VitoEnergy required two bespoke hot water cylinders, a buffer store for the heating and an unvented ECOflow for the properties hot water.

The 200 litre buffer store was designed to utilise the heat provided initially from the oil boiler, solar thermal and also via a 6kW immersion heater, which was powered in part by flexible electricity tariffs from Octopus Energy. It was also future proofed with the provision for solar PV to power the immersion and a ground source heat pump (with an option to introduce an air source heat pump).

The 350 litre unvented ECOflow provided the properties hot water requirements. The cylinder was bespoke designed to accommodate the solar thermal coil, an oil boiler coil and a 4m2 double pass heat pump coil which incorporated two 22mm integron coils running in parallel connected into the internal manifold and with 28mm external connections, allowing for higher heat transfer and lower pressure drop to maximise the heat pump efficiency and reduce running costs. In addition, there was also a 6kW immersion connected to the flexible electric tariff but also suitable for use with solar PV input.

Once the heating and hot water was satisfied, the remaining heat was then diverted to the outdoor swimming pool.

The heat from the various sources were delivered to the cylinders by an ingenious network of external pipework which can be seen in the video put together by the educational resource Heat Geek at

As you can see, the flexibility of copper cylinder production came to the fore in this project, providing the installer and ultimately the homeowner a tailored hot water storage solution to meet all their requirements.


“McDonald Water Storage adaptability and thoroughly tailored solutions suit my eye for detail and doing things ‘right’ very well. Their engineers completely understood what we were going for and delivered the solution at a very reasonable cost. Totally happy.”

Adam Chapman, Director, VitoEnergy

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