Thermal Store

thermal store

A thermal store is a device used to store heat energy in the form of water.

Thermal stores can be used to store heat from a variety of sources, including electric, gas, solar thermal and solid fuel boilers. They can be used to provide either domestic hot water only or wet central heating and domestic hot water.

The MULTIflow thermal store range is specifically designed for the contract market, to provide a high performance, mains pressure hot water solution which delivers enormous benefits.


This thermal store approach can suit many installation applications, including electric, boiler or central plant inputs to meet hot water demand.
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The MULTIflow+ thermal store is an extension to our MULTIflow range, providing a high performance, mains pressure hot water solution for the contract market, but with the additional benefits.


The new MULTIflow+ allows for bespoke design flexibility to suit the specific installation requirements including adjusting the tapping positions or utilising slimline models.
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CUBEflow providing the space saving solution for space restricted installations, with the tank design taking up 27% less space than an equivalent cylinder.


The range of copper hot water tanks deliver mains pressure hot water, with both standard and bespoke models that can be heated electrically, or indirectly by a gas or oil boiler, or renewable heat sources.
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The ELECTRAflow provides primary hot water to heat a standard “wet” radiator system whilst also providing the domestic hot water.


ELECTRAflow provides the comfort and convenience for a wide range of properties including new housing, multi-storey buildings, rural housing and off-gas areas.
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The ELECTRAstore is a market first thermal store designed to maximise the benefit of time in use tariffs to provide hot water to heat a standard “wet” radiator system whilst also providing the domestic hot water.


ELECTRAstore is a bespoke electric thermal store which incorporates our innovative IOT control system with self learning algorithm, to store energy when it’s provided at low cost and low carbon, to be used when needed.
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CENTRALflow heat interface unit provides a unique and energy efficient heating and hot water storage solution for apartment blocks or properties where the heat comes from a centralised source such as a biomass or CHP Plant.


CENTRALflow delivers mains pressure hot water through a thermal store linked to a Heat Interface Unit (HIU) which can also offer a Heat Metering facility.
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  • Delivering Mains Pressure Water
  • Easy to install – does not require G3 certification
  • Requires no annual maintenance
  • Specialists in like for like replacements – even for other manufacturers
  • All our thermal stores are manufactured from copper – kills bacteria such as legionella
  • Built in scald protection
  • Models for both heating and hot water or hot water only
  • Rectangular and Slimline Units Available
  • Recommended by professional contractors and specifiers
  • Ideal for homes and commercial buildings

Our focus is very much on the manufacture of copper hot water cylinders and tanks. Copper provides fantastic benefits including;

  • Ability to kill 99% of bacteria including Ecoli and legionella
  • One of the most efficient conductors of heat
  • Significantly more flexible for manufacturing than other materials
  • Long lifespan due to its amazing resistance to corrosion
  • 100% recyclable


For further information see our brochure The Ultimate Supermetal or visit our Copper Facts page.


A thermal store is a device used to store heat energy. Thermal stores can be used to store heat from a variety of sources, including electric (immersion heater), gas, solar panels (thermal or PV) and solid fuel boilers. Thermal stores can be used to provide not only domestic hot water but also heating.

Thermal StoreA thermal store is a device that stores heat in the form of hot water. It is made up of a store of water that is heated by a heat source, such as a boiler. The tank is insulated with either injection foam or spray foam insulation, to prevent the heat from escaping, and the pipes are designed to minimise heat loss.

Domestic hot water is generated when mains pressure cold water passes through the internal heat exchanger, then blended with cold water to 55 degrees, and delivered to the taps.

The heating system can be supplied either directly from the store or via a separate internal heat exchanger.

For further information click here.

There are many benefits to having a thermal store in your home or commercial buildings, with one of the major ones being it can take the energy when it is at its lowest cost for use when it is required.

A thermal store is also inherently safe not only being an open vented store, but with the domestic hot water being mains cold water instantaneously generated, there is no risk of legionella. The use of the blending valve to control the hot water temperature provides home owners with anti scald protection.

In addition, there are no ongoing servicing requirements as associated with unvented cylinders, therefore reducing running costs.

The benefits of a thermal store are highlighted by the Energy Savings Trust.

A thermal store is installed by connecting it to the mains water cold water supply and the central heating system (where applicable). The store is then filled with water and the temperature is set. The store can then be used to heat the water for the central heating system or for domestic hot water.

A thermal store can be situated virtually anywhere within the home as long as the header tank is higher than the radiators (when used for heating).

The installation does not require the installer to have G3 qualification, as with unvented installations.

For further information click here.

There are a wide range of thermal stores available, whether it is electric only, for use with a central plant boiler, multi fuel application to name but a few. With options not only for hot water but heating itself, the range is extensive.

Contact our technical team who will be able to help specify the correct product for your application and answer any questions.

A thermal store can prove to be an innovative solution within off-grid properties with multiple heat sources. The thermal store would only use mains electricity, expensive oil or LPG as a top-up, when the other sources weren’t providing enough energy to meet the properties requirements.

The thermal store is the perfect partner for renewable heat sources, maximising the benefits with the ability to use for both heating and hot water.

Being open vented, it is suitable for uncontrolled heat sources such as pellet or wood log burners, in addition to the solar thermal and electricity generated by wind or hydro generation. The cylinder or tank can take the heat input when it is available and stores thermal energy for use when the property requires it, which is a major benefit to energy providers.

Thermal Store SchematicIn a thermal store, the water held in the tank is used to provide the energy to meet the properties heating and hot water requirements.

There are generally two approaches to the design and manufacture of a thermal store. Firstly the coil based thermal store and secondly, thermal stores featuring an external plate heat exchanger (PHE).

With the coil type thermal store, the domestic water passes through a high efficiency copper coil, drawing heat from the surrounding thermal store of water, to deliver mains pressure hot water. This water is blended with cold water via a thermostatic blending valve to 55 degrees, and delivered to the outlets at the required temperature.

The thermal stores can utilise an external Plate Heat Exchanger, however this method uses a far more complex way of delivering hot water and features more components – pump, PHE, flow switch and wiring centre, while they work extremely well, there are obviously more components to potentially go wrong.

The space heating can be provided either directly from the store or via a separate internal heat exchanger.

Manufacturing from copper, McDonald Water Storage can manufacture a thermal store to suit the installation requirements. Whether this is a cylinder with separate F&E tank, cylinder with a combined F&E tank, or even a rectangular tank where space availability is severely restricted.

A thermal store is a higher purchase cost compared to an unvented solution. However, when comparing hot water solutions it is important to consider the following;

  • There are no annual service requirements with a thermal store, but that is required with the unvented alternative
  • Thermal stores do not require discharge pipework, providing a perfect solution for multi occupancy developments and reduce installation time and cost
  • The ability to provide both space heating and domestic hot water is only possible using a thermal store.
  • A thermal store does not require a G3 qualified engineer to install