thermal store

A thermal store is a device used to store heat energy. In turn, they provide the ability to deliver both space heating and mains pressure hot water, by storing and managing heat distribution.

As a result thermal stores are becoming increasingly popular in domestic settings.

Thermal stores can be used to store heat from a variety of energy sources, including electric (immersion heater), gas, solar panels (thermal or PV) and solid fuel boilers.

A Thermal Store is one of the most popular types of hot water cylinders, especially in rural locations where multiple fuel sources are being used and high rise developments where mains pressure is required without the discharge complications that an Unvented cylinder can bring. But how does a thermal store work?

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).

Coil Type Thermal Store

With the coil type thermal store is the most popular and simplest solution. The domestic water passes through an extra-long high efficiency copper coil, drawing heat from the surrounding thermal store of water, to deliver mains pressure hot water at the required temperature.

The coil type thermal store offers many benefits over the plate heat exchange model, mainly due to the simplicity of the system. The use of the coil means that there are less moving parts and therefore is less likely to go wrong. This makes them particularly attractive in rural locations, where power cuts are more likely and in social housing developments where access for repairs can be difficult.

Plate Heat Exchanger Thermal Store

A thermal store with external Plate Heat Exchanger, on the other hand, 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 external Plate Heat Exchanger approach was originally developed to overcome the inferior thermal transfer properties of stainless steel. The method directs the cold mains through the flow switch and one side of the PHE, which then activates a primary pump to circulate the thermal store water round the other side of the PHE.

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 differs from a conventional hot water cylinder as the stored water is not delivered to the taps directly from the thermal store. Instead, it is heated up by passing through an internal coil (heat exchanger) that transfers heat from the thermal store water to the mains cold water, and is blended down to 55 degrees before being delivered to the hot water outlets.

Another difference is that a thermal store has the ability to supply the wet central heating system, whether it is underfloor heating or traditional radiators, not possible with an unvented cylinder.

The switch from conventional gas boilers or in the instance of multiple occupancy developments, gas fired central plant systems, can be problematic when looking for a heating and hot water system that is both cost effective at the time of purchase, but is also efficient to run.

Electric combination boilers are often seen as the answer with several advantages, such as being small, clean and easy to install. However, there are also disadvantages to this go to solution.

Thermal storage systems on the other hand, not only provide the same benefits over gas powered systems but can also ensure ongoing running costs are kept to a minimum. In addition, this energy storage potential only provided by a cylinder, enables the balancing of demand on the electrical grid, and reduce the reliance on peak periods.

So will it be thermal storage or electric combination boiler?

Before making the choice between an electric thermal store or an electric combination boiler to provide both the heating and hot water for your property, it is worth considering the benefits of thermal stores. Click here to see the additional benefits our electric thermal stores, ELECTRAflow and ELECTRAstore, can provide over an electric combination boiler.

There are many benefits to having a thermal store in your home, with one of the major ones being is it is open vented, providing the mains pressure hot water without the complexities of an unvented option.

A thermal store is 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.

There are also no ongoing servicing requirements as associated with unvented cylinders, therefore reducing running costs.

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.

In 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.

With many manufacturers changing their product range, discontinuing thermal storage or pushing alternatives such as stainless steel with completely different connection layouts, having a different footprint and not fitting into the existing installation area, we have seen a steady rise in enquiries from installers and homeowners who would prefer a direct replacement for their existing thermal stores.

This is where McDonald Water Storage, the thermal store specialists, can provide you the perfect replacement solution, being the only hot water cylinder company in the UK to specialise in manufacturing like for like replacements for any existing copper thermal store.

We are able to provide the perfect replacement solution for products including Albion Mainsflow, Elson Coral E and Coral Si, all models of Gledhill PulsaCoil, to name but a few.

Click here to see full details of the complete range of thermal store solutions.

With many technical challenges surrounding boiler sizing, diversity requirements and pipework infrastructure, localised water storage can provide significant benefits. Having the localised storage means that the boiler size and therefore pipework infrastructure can be dramatically reduced in size, saving money and building the efficiency of the system by smoothing out the running load of the boiler.

We have been championing the benefits of hot water storage for many years, and the Hot Water Association lists no fewer than 22 advantages of using stored hot water over instantaneous systems. Using stored hot water solutions within heat networks has many advantages over systems that generate hot water instantaneously.

See our dedicated page providing further information on the benefits of hot water storage within heat networks.

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 provide a perfect solution, whether in an electric only apartment where the homeowner wants to maximise the benefit of off-peak  tariffs or through renewable technology.

In an electric installation, the thermal store temperature can be raised to store more energy. For instance, the ELECTRAflow temperature can be raised to 90 degrees, providing 150% increase in stored energy over an unvented cylinder that is held at 60 degrees.

The thermal store is also widely recognised as an optimal solution for incorporating renewable energy inputs, thanks to its ability to harness the energy as it is generated, store it until it is required, and then transfer the heat into heating and hot water on demand.

By incorporating multiple renewable energy sources, you can create a truly efficient solution using, for example, solar to capitalise on the energy generated in the summer months, with a solid fuel stove generating the power during the colder winter months.

The thermal store is also widely recognised as an optimal solution for incorporating multiple heat sources, maximising the efficiency thanks to its ability to harness the energy as it is generated, store it until it is required, and then transfer the heat into heating and hot water on demand.

By incorporating multiple renewable energy sources, you can create a truly efficient solution using, for example, solar to capitalise on the energy generated in the summer months, with a solid fuel appliance burning fuels such as biomass, wood pellets or wood, generating the power during the colder winter months.

See the diagram below highlighting the flexibility of energy inputs within a THERMflow thermal store.

The thermal store is designed to work best when the store temperature is at or approaching 70°C – 75°C. While the thermal store can provide hot water at lower temperature storage, the available flow rates and volume will be reduced. Check the thermometer is showing the store temperature is at or approaching 70°C -75°C.

High temperature thermal stores such as the ELECTRAflow and ELECTRAstore models can raise the stored temperature to 90°C, allowing for a larger capacity of energy storage. These products utilise a temperature sensor at the top of the unit as opposed to the immersion control thermostat.

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 boilers 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 wet central heating systems 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.

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.

Our technical team will be able to provide advice on the best thermal store solution to meet your installation requirement.

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 a wet central heating system and domestic hot water is only possible using a thermal store.
• A thermal store does not require a G3 qualified engineer to install