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Thermal Store Installation

Thermal Stores

Thermal Store installed without discharge pipework

This section is titled "Thermal Stores" but what exactly is a Thermal Store?

A Thermal Store is a very adaptable Domestic Hot Water solution and can provide much better Domestic Hot Water performance to the conventional "Open Vented" Cylinder.

The flexibility of the Thermal Store is the reason for its sucess, it can be adapted for almost any type and number of heat sources. If you are interested in combining Multiple Heat Sources, we would suggest visiting our specific page on this specialist application.

Thermal Stores have the ability to be configured to suit most installations and can be potentially installed without the requirement for discharge pipework.

The low Domestic Hot Water performance could result in baths taking an excessive time to fill and cause showers to perform below expectations.

The cold main into your property is likely to have over 1.0 bar of standing pressure and is often between 3.0 to 4.0 bar, increasing the suitability of a Thermal Store.

If the pressure is above 4.0 bar, it is worth considering a pressure reducing valve for reliability and consistance of performance.

Good standing pressure alone is not a guarantee that the cold main is suitable for a thermal store, as the operating pressure and flow must also be verified.

Once the cold main has been confirmed as suitable for requirements, we have the potential to deliver Domestic Hot Water at the pressure and flow, nearly equal to the pressure of the cold main. If a Thermal Store is being considered, the advantage of high pressure showers and fast filling baths at your finger tips.

If you wish for your Thermal Store to be repaired, replaced or serviced, simply call us on 01206 432 999.

Do you own an existing Thermal Store and are interested in Heat Lab Ltd improving the delivery of your Domestic Hot Water?

The performance of the Unvented Cylinder can be improved primarily by increasing the water pressure available to the cylinder inlet. This can be done by increasing the diameter of the cold water main (not always possible/effective) or install some form of boosting equipment, as detailed below;

All of these products are available from ourselves and have a thorough description in their relevant section of this website or just click on the description above.

To appreciate the how the Thermal Stores operate, we have information below outlining the operation of the equipment and the components involved.

The Technical Side of Thermal Stores

This section will explain the key differences between each type of Cylinder and will also show schematics for their conventional installations.

Open Vented Cylinder

Open Vented Cylinder Schematic

The Open Vented Cylinder has been used since the inception on Hot Water Systems and generally gives years of service without problems.

The main problem with the Open Vented Cylinder is a potential lack of water pressure and/or flow.

The cylinder can be heated directly by an immersion heater or indirectly from a heating appliance on a "S", "Y" or "W" plan.

The installation is flexible in design, allowing boosting pumps to be installed on Showers or any other outlet requiring superior performance.

It is referred to as an "Open Vented Cylinder" as the cylinder is open to the atmosphere and is vented to the highest point in the system, the Cold Water Storage Tank.

The vent pipe is shown in red on the schematic on the left and runs from the top of the cylinder, to over the top of the cold water storage. This pipework must raise vertically and also, be over a minimum diameter.

When the cylinder is heated, by whatever means, the water inside the cylinder expands and if not allowed to escape, will cause the cylinder to fail. The expansion is intended to travel up the vent pipework and will also cause the water level within the cold water storage to rise.

A recent addition has been the addition of a temperature and pressure relief valve on the cylinder itself. This is a safe guard to prevent the cylinder failing in the event the vent and feed pipework to the cylinder becoming blocked.

With open vented type hot water cylinders, the system relys on the height difference between the cold water storage tank and the hot water outlet, every one metre of height difference equates to approximately 0.1 bar of pressure.

Thermal Stores - Base Model

As you can see from the schematic below for the Direct Thermal Store there is no Cold Water Storage Tank at the highest point in the system and as a result, less space is generally required for installation.

Thermal Store Schematic

There are numerous reasons for specifying a Thermal Store, to increase Domestic Hot Water Performance, integrate another Heating Appliance or the requirement for a Domestic Hot Water Solution that requires practically no maintenance, useful for Landlords.

The Cold Water Main must be capable of providing sufficient pressure and flow for the requirements of the property.

If the water pressure and/or flow is below the level required, please refer to our products and solutions for Cold Water Boosting in the links above.

When the Thermal Store is heated, by whatever means, the water inside the cylinder expands and is absorbed by the expansion vessel, the movement of an air bladder within to be precise. Hover over the image above and it will show the water expanding into the system expansion vessel.

The sizing of the thermal store is slightly different due to the additional heat exchange that is required and as such, 20% additional capacity is added in comparison to a conventional cylinder.

Therefore the number of baths, showers, hot water outlets and expected use are all required to finalise the initial capacity, before the 20% allowance is included. Some very detailed information on sizing and dynamic flow through a cylinder is available in the section on Buffer Tanks and can be found here;

Safety and Controls

The Thermal Store is inherently safe as the volume of stored potable water (at a high pressure) is much less and as a result, the installation of the Thermal Store does not constitute "controlled works". The therefore does not require specialist certification.

The next two components from left to right are seperate but work together for functionality;

Thermal Store Thermostat and 2 Port Valve

Collectively, these components control the temperature of the Thermal Store and due to the nature of the design, does not require an energy cut out.

The operation of the 2 port valve is controlled by the Thermostat "calling for heat", opening the 2 port valve and enabling the appliance accordingly.

If you are familiar with unvented cylinders, you will be aware of the Temperature and Pressure Valve but this is not required on a Thermal Store, as the body of water is not repressurised by the cold main.

Immersion High Limit Cut Out Unvented Cylinder

To the left is the Immersion Heater Thermostat and the connecting mains electricity cable, of which must be rated for the high temperatures encountered.

The Immersion Thermostat must feature a high limit cut out (circled) and it must not automatically reset.

If the high limit thermostat activates, the reason for the overheating must be investigated and rectified prior to resetting.

Immersion heaters are now commonly connected to Solar PV Installations and controlled by a Solar Controller, similar to an "Immersun" diverter. This enables the Immersion heater to consume any energy that would be otherwise be exported to the mains national grid, effectively providing free Domestic Hot Water and also, a very low carbon footprint.

Like an conventional cylinder, a Solar PV diverter such as an "Immersun" can use provide free Domestic Hot Water and uniquely with a thermal store, can also contribute to space heating.

If an Immersun controller is used, it is often worthwhile specifying two 3kw Immersions, one in the bottom of the cylinder and the second in the mid section. The upper immersion is the primary heating element and is utilised initially, especially useful in periods of low solar gain. The secondary Immersion is located in the bottom section of the cylinder and is used in periods of high solar gain, where it is possible to heat the complete cylinder.

Good Pressure and Flow from an Unvented Cylinder Two Showers from an Unvented Cylinder

Two reasons why Thermal Stores can be so effective, luxurious Water Pressure and Flow to quickly fill large baths or run multiple showers.

If the water pressure in your property is insufficient, there are methods that can be adopted so almost any requirement can be accomodated.

This technology can be applied to almost all systems, including most renewable energy heat sources. If connecting to some low temperature heat sources, specialist options with large plate heat exchangers must be specified and installed.

If you are located within a hard water area, a thermal store is less likely to deteriorate but a suitable form of water treatment is required.

When considering a Thermal Store, it is important to consider that they require NO annual servicing.

Tel. 01206 432 999