The GXV Heat Bank Thermal Store provides up to 30 litres per minute of mains pressure hot water using our latest high efficiency plate heat exchanger technology. The use of a plate heat exchanger keeps the stored water completely separate from the mains water supply. This allows the use of a vented storage cylinder, and removing the need for cold water storage.

The hot water supply is not stored and may therefore be used for drinking, without the dangers of Legionnaire's.

The small size of the unit, typically 80 litres, ensures rapid recovery from a standard boiler. Following a bath, a 12kW (40,000 Btu) boiler can recover the entire store within 20 minutes.

The greatest problem that faced us when designing the GXV was obtaining the large volumes of hot water that were demanded from such a small unit. After a year of experimenting with various systems, we developed a way to extract nearly 100% of the stored heat, and at the same time ensure that 100% of the boiler output went directly to the taps.

This combination of stored heat and boiler input finally allowed us to fill a bath at 25 litres per minute to 43°C, with surplus stored heat left in the store. In factory tests the GXV provided 170 litres at 45°C, and at an average flow rate of 25 litres per minute.

The methods we used to achieve this also provided hot water within 3 minutes of cold start.

A benefit of the patented method used to recover the stored water, is the ability of the GXV to automatically control the return temperature to the boiler.

To achieve the maximum efficiency from a condensing boiler the return to the boiler must be kept below 55°C. The GXV will hold the return to the boiler at a pre-set temperature, typically 53°C, until the entire store has been heated to this temperature. During this recovery, the boiler will be continually in condensing mode and will not cycle.

Energy efficiency is further increased as a result of the small capacity of the unit. With such a small surface area heat losses are minimised. CFC free factory foam insulation, combined with pipe insulation, keeps stored heat locked away.

Water and heat waste is reduced by the extremely fast response times to taps. When a tap is opened, the hot water supply temperature jumps nearly instantaneously to the set output temperature on the thermostatic blending valve, so that the user does not have to run off water waiting for the temperature to climb to a suitable level. The fact that the water is at mains pressures also enable the use of small bore pipework, further reducing water waste.

To reduce energy loss through central heating, the units make use of a programmable room thermostat that provides accurate control of room temperatures, allowing different temperatures to be set for different times.

For example, night setback setting can be easily programmed. This method provides more precise control of the central heating load, thereby increasing the overall system efficiency.

Solar Applications: It should also be noted, that a solar version of the GXV has also been developed. The small storage size required with a GXV unit for domestic use make it ideal for solar applications. A typical 250 litre domestic solar cylinder requires the gas boiler to heat up around 115 litres of water for domestic use, leaving 130 litres dedicated to solar heating. A similar sized GXV unit, requiring only 80 litres for domestic use, would provide 170 litres for solar use. This additional solar storage increases the gains from solar panels and the energy efficiency of the entire system.

Any system components that have to be fitted by the installer, because they cannot be pre-fabricated, should be simple to connect, requiring the minimum of additional on-site work.

With all components factory fitted, wired, and tested, the local authority could then rest easy in the knowledge that the hot water and heating systems in properties fitted with a GXV had been put together properly.

In addition to the Heat Bank Thermal Store controls, the GXV Heat Bank Thermal Store is factory fitted with all the usual domestic hot water and heating system controls, as follows:

Domestic Blending Valve
Primary Circulating Pump
Motorised Three Port Valve
Cylinder Thermostat
Wiring Centre

The only part of the control system that cannot be factory wired is the room thermostat. We were able to overcome this by using a Danfoss TP5E RF room thermostat and RX1 digital radio receiver. The room thermostat communicates with the receiver, fitted and wired to the Heat Bank Thermal Store, using a digital radio signal. The room thermostat runs for two years of two standard AA batteries, requires absolutely no wiring, and can be easy positioned (or re-positioned) to suit.

The installer is now faced with a very simple installation procedure.

Pipework connections:

The way that the GXV unit operates also removes the need for a balancing valve between the boiler and the store.

System Adjustment:

All system components are factory pre-set to work with a typical domestic central heating installation. The only controls that may need adjusting are:

1. The domestic blending valve - to take account of the users personal preferences regarding the hot water supply temperature. The blending valve head can be locked at a pre-determined setting.
2. The room thermostat – to suit the users requirements.

To provide greater flexibility in design and installation, we developed along-side the GXV, the GX Heat Bank Thermal Store for a sealed systems.

Where the installation will not allow the fitting of an F&E tank, the GX overcomes the problem by the use of a built in expansion vessel. The entire GX and heating system is pressurised, and no separate F&E tank is required. The GX is fitted with all the usual sealed system controls including:

Expansion Vessel
Pressure Relief Valve
Pressure Gauge
Overheat Thermostat
Filling Loop

Any hot water or heating system is only as reliable as its individual components. That is why we have made sure that every component used in the GXV has been tried and tested to work in the field.

All assembled pipework is made to the highest standard using high quality fittings and jointing compounds to ensure leak free commissioning.

The cylinders themselves contain primary water, and so are protected against scale. A corrosion / scale inhibitor may be added to the store to provide added protection to the complete system.

One of the greatest problems that service engineers face is the inaccessibility of controls, preventing them from being easily serviced.

We have therefore made it a high priority, in designing the GXV unit, to position all components where a service engineer can be certain to reach them.

To make sure of this we fully serviced every component on the unit ourselves. Whenever we came across a potential situation, we repositioned the necessary components to ensure that it was overcome.

As a further check we asked an installer to service the various components. Any suggestions that were put forward to make servicing easier were implemented in the design.

Finally, full maintenance instructions, including such information as the system wiring diagram and fault finding chart, will be supplied with each unit.

Bosses, pipes, and controls are clearly labeled to assist with the installation of external pipework connections.

During a  demonstration conducted using a GXV Heat Bank Thermal Store in conjunction with the Vaillant VU186EH condensing boiler, the following procedure was followed, and readings taken:

1. The boiler was fired and left to fully heat up the stored water.

2. The hot water outlet into the bath was fully opened.

3. 120 litres was drawn at an average of 50°C and an average flow rate of 25 litres per minute.

4. Without pause, a further 50 litres was drawn, to make a total of 170 litres of water at 45°C.

5. The hot water outlet was closed and the system left for only 3 minutes to recover.

6. The hot water outlet into the bath was then opened again.

7. A further 15 litres of 45°C water was drawn – sufficient for a basin or sink.

8. The hot water outlet was closed and the GXV Heat Bank Thermal Store left for 23 minutes to recover.

9. The hot water outlet into the bath was again opened.

10. A further 160 litres at 45°C was drawn off.

11. The entire test was then repeated with very similar results.