The first, and main reason, why someone would want a thermal storage unit, is to allow the householder to generate pressurised hot water for more than one outlet at once.  

To make a simple comparison a wall hung gas combination boiler will generate typically 30kW hot water, equal to 12 litres every minute at usable temperatures. A thermal store, typically rated at 100kW, can generate 40 litres per minute at the same temperature - more than 3 times as much.  This simple fact of physics is why hot water storage of some sort is always required if you intend to properly supply more than one tap at once.

A second is to do away with cold storage tanks, making hot and cold water clean and drinkable and providing a free loft space.

And a third is provide a mains fed system that is easy to install and maintenance free.

Heat Bank Thermal Stores are advanced hot water thermal storage units, providing high flow rates of mains pressure drinkable hot water. 

The Heat Bank Thermal Store stores Heat Energy which can be utilised to provide domestic hot water or even central heating if required. This heat energy is transferred to mains water by a plate heat exchanger.  

No domestic water is stored, hot or cold.

The standard range of Heat Bank Thermal Stores are unpressurised and fully vented to atmosphere, with the option to have an Integral Feed & Expansion (F&E) Tank or to connect to a remote F&E Tank.

The water within the Heat Bank Thermal Store (stored water) can be heated by various methods, including Gas/Oil Boilers, either directly or indirectly (using a coil), or by Electrical Immersion Heaters utilising various tariffs.

The mains hot water is not stored and is therefore drinkable, and removes the need for a cold water storage tank. There is no chance of the introduction of Legionnaires’ Bacteria into the domestic supply.

Operation:

1. When a hot water outlet is opened the resulting flow of water is sensed by the Flow Switch, which in turn switches on the Heat Bank Thermal Store Pump.

2. The Pump draws hot stored water from the top of the Heat Bank Thermal Store and passes it through the Heat Exchanger and back into the bottom of the Heat Bank Thermal Store below a diffuser plate. This plate prevents turbulence within the unit and keeps the stored water stratified, thereby increasing efficiency.

3. As the stored water passes through the Heat Exchanger its heat is rapidly transferred to the Mains Water also running through the Heat Exchanger but separated from the stored water by numerous plates.

4. When the hot water outlet is closed, the Flow Switch will turn off the Pump, thereby using energy only when required.

This method of heat transfer, referred to as forced convection, affords heat transfer rates of up to 100kW (340,000 Btu/h), thereby providing mains pressure hot water at up to 45 litres per minute, raised through 35°C (see output graph below). In addition, more than one heat exchanger may be fitted to double, or even triple, the mains water output.

The plate heat exchanger:

The plate heat exchanger separates the pressurised mains water from the stored water. While the mains water pressure can be anything from 0.5 to 6 bar, the stored water is not pressurised, allowing the Heat Bank Thermal Store to be vented to atmosphere.

The compact brazed plate heat exchanger, shown here in cutaway, is fitted internally within the Heat Bank Thermal Store and is manufactured from corrosion resistant steel and tested to 15 bar pressure.

All Heat Bank Thermal Stores are fitted with internal diffuser tubes or plates to prevent turbulence caused by water returning from the heat exchanger. This helps to keep the stored water well stratified, increasing the volume of available hot water, and thereby increasing the total supply of hot water that can be drawn from the Heat Bank Thermal Store.

The stored water never changes. The build up of scale within the cylinder is therefore eliminated and extra system protection is achieved by the addition of corrosion / scale inhibitors. If required, anti-freeze may also be added.

The stored water can be heated to a maximum of 90°C thereby increasing the amount of heat energy available for use, while the use of CFC Free Foam Insulation (to British Standards 699, 1566 & 4735) contains the heat within the stored water.

Heat Bank Thermal Store Units are available in three basic types:

Pandora Heat Bank Thermal Stores are fitted with an integral vented Expansion Vessel. The stores are manually filled, with a hose, having no overflow or discharge pipes.

Everest Heat Bank Thermal Stores are fitted with an integral Feed & Expansion Tank. Units are fitted with Cold Feed and Vent pipes, as well as a Ball Valve (unless the Solenoid Feed Option is requested), an Overflow Connection and an Aluminium Lid.

Xcel Heat Bank Thermal Stores are to be used where additional head is required for the Primary System, via connection to a separate Feed & Expansion Tank - F&E Tanks can be supplied fitted with a Solenoid Feed if required. This tank must be large enough to accept the expansion (4% by volume) from the Heat Bank Thermal Store unit, as well as the Primary System. Xcel Heat Bank Thermal Stores are fitted with Cold Feed & Vent connections.