GX Heat Bank

Integrated Thermal StoragePatented DPS Technology

For provision of domestic

hot water and heating

from any combination

of heat sources

Approved System

The GX Heat Bank range from DPS is designed to make the most ofintegrating a store of hot water into a boiler and heating system.The water in the storage cylinder is the same water that flowsthrough the boiler and radiators - it does not come out of the taps,and never changes. Hot water to taps is provided by heating upmains water as it is required, using stored heat.

It was originally designed as a rapid recovery hot water system thatwould make the most of available boiler output to back up storedwater. The goal was to provide a bath and shower simultaneously,with showering to continue indefinitely, all from a 90 litre cylinderthat would fit under a kitchen worktop. This could not be achievedthrough conventional indirect storage, even using the highest recov-ery coils, however the GX easily achieves these goals, with a numberof other equally important benefits.

For a start, the GX is a vented storagesystem, so the building regulations thatapply to unvented mains storage can beignored. No requirement for a specialistinstaller, no safety valves, no annualmaintenance buy a qualified engineer,and the ability to connect to unregulatedheat sources.

Despite being vented however, the GXcan deliver drinkable mains pressure hotwater up to 9 bar pressure (90 metreswater head) and flow rates from 30 to90 litres per minute, enough to runnumerous taps at the same time, mainssupply providing. Once the store has

been run cold, hot water can still be obtained (at lower flow rates)using the available boiler output, similar in effect to a combinationboiler.

Unregulated heat sources that the GX can connect to include solarsystems, wood burners, and biomass boilers, and it does so in a waythat lets the use decide what the various heat sources are used for,and how much of any backup heat sources are used, such as a gasboiler or electric.

Central heating is provided by pumping water directly from the storeto either radiator, underfloor heating or towell rails. Where there is acombination of radiators and underfloor heating in a property, theGX will account for the fact that the radiators need hotter water,allowing the underfloor to run off solar while the gas boiler or elec-tric are used for radiators.

The GX effectively provides storage for all the technologies requiredfor alternative or zero-carbon provision of domestic mains pressurehot water and central heating.

Sounds like a complicated system ? Well no, as the system is farsimpler in general design, with no motorised valves, no expansionvessels, no pressure discharge pipes, and no filling loops. The factthat all boilers, and optionally the solar, are now a single systemreduces the overall complexity. A single header tank is used to auto-matically fill and keep the entire system topped up.

The storage cylinder itself can be DIY installed and maintained, how-ever heat sources such as gas boilers or high current electrical sup-plies for heaters will have to be installed and maintained by certifiedinstallers. The only maintenance requirements on the GX are the

occasional addition of corrosoin inhibitor into the system every 3 to5 years, as you would to any heating system.

But it gets even better... Wheras other hot water systems usuallycome in component form, with the installer required to fit and wireall controls, the GX can be supplied full factory pre-fabricated. Unitsare typically supplied as ‘nearly-finished’ systems, where all thepumps, programmers, valves, thermostats and heaters have beenfactory fitted, wired and tested, reducing the site installation to littlemore than connecting to pipework.

Next up on the benefit list is the range of sizes. Being a venteddomestic system allows specials to be made without any approvalrequirements, and this means that the range covers sizes from 80 to500 litres, in four diameters of cylinder, and with rectangular optionsavailable. The ability of the store to reheat quickly makes it smalleranyway, but the added options to go tall and thin, or short and wide,allow spaces to be utilised that would otherwise be impossible.

Is this new ? No is the simple answer. GX Heat Banks have beenaround for over 10 years, and have been used by local authoritiesand in thousands of private households al over the UK. It is triedand tested to work, with testimonials from official bodies as well asmany very satisfied customers. You don’t need to take our word forit, just look on the main UK DIY internet forums for discussions onthe GX and Heat Banks.

The system is further backed by 1 year on-site backup, and twoyears warrantee on all components.

A Comparion to Others.

The following table sums up the differences of various hot watersystems available on the market.

At DPS we supply ALL types of hot water system, and the GX is verydifficult to beat in any catagory. Add all the advantages all togetherand it becomes clear why the GX is our flagship product.

Type of System CombinationBoiler

Tank FedCylinder

DomesticUnvented

GXHeat Bank

Mains Pressure Hot Water 6 Bar No 3 Bar 9 Bar

Maximum Flow Rate (typical). 12 ltr/min 30 ltr/min 30 ltr/min 40 ltr/min80 ltr/min

Annual Maintenance Yes No Yes No

Specialist Installers Required CORGI No UNVENTED No

Work with Gas/Oil Boiler Yes Yes Yes Yes

Work with Electricity No 3 kW6 kW

3 kW6 kW

3kW30kW

Work with Solar No Yes Yes Yes

Work with Wood Burner - Yes No Yes

Work with Heat Pump No Yes Yes Yes

Buffered Central Heating No No No Yes

Fast Initial Heating Response No No No Yes

Electric/Solar Central Heating No No No Yes

Special Sizes to Request No Yes No Yes

Source to Load Matching No No No Yes

The multifuel version of the GX Heat Bank is shown here, and asstandard comes fitted with the following:

Pumped boiler circuit with return tem-perature control and two store temper-ature control thermostats for efficientboiler control.

Two independant heating circuits, forcombination of radiators, underfloorheating or towell rails.

Connections for wood burner or solidfuel cooker (pumped or gravity).

Coil for solar panels or alterative heatsource, with sensor pockets.

Connections for heat pump, with sen-sor pocket.

100kW mains hot water plate heatexchanger assembly with temperaturecontrol.

3kW immersion heater.

Wiring centre with all fitted controlswired and tested.

Connections for header tank.

Spare sensor pockets overheat signalto initiate heat dump.

Drain cock.

Additional bosses can be provided on request.

The following example shows how far the options can go in terms ofpre-fabricated factory fitted and wired controls, aimed at savinginstallation time, cost and training requirements:

Radiator circuit pump.

Underfloor heating flow temperaturecontrol and pump for systems up to300m square.

Economy immersion heater, witheconomy tariff timer and run-downtiming for boost heater.

Bronze pump for mains hot watercirculation, to remove dead-legs totaps and reduce water wastage.

Two channel programmer for controlof boiler and secondary return cir-culation.

Programmable room thermostat(supplie loose) with RF radio com-munication, for wireless installation.

RF reciever unit for connection toroom thermostat and control ofheating pumps.

Overheat thermostat to initiate cen-tral heating to prevent excess storetemperatures.

Electronic anti-scale device to pro-tect all components in contact withmains water from scale deposition.

Mains Pressure Hot Water.

Hot water to taps does not come from the store. Instead, mainswater coming directly into the property at high pressure is passedthrough a plate heat exchanger, where it is heated using the heatfrom water in the top of the store.

The plate heat exchanger comprises of numerous stainless steelplates that provide a very large surface areafor heat transfer. They can be sized to heat asmuch mains water as can be supplied by themains, with standard models providing between24 and 90 litres per minute; easily enough forany domestic application. The plates keep thestored water completely seperate from themains water, and can withstand working mainspressures up to 35 bar (10 bar on standardversion).

Central Heating.

Central heating is pumped directly from the store. This allows any ofthe sources used to heat the store to be used for both hot waterand/or heating. Heating is typically fed from the lower half of thestore, thereby providing a hot water reserve for generating hot waterto taps that can’t be used up for heating.

There can be as many circuits fed from the store as needed, withprovision for two circuits as standard toaccommodate two heating-zones, or a combination of radiators and underfloor heating.

Effective Control of Boiler.

One of the basic principles behind the GX is the way it controls theboiler circuit. One aim of the design is to obtain full boiler outputfor immediate use, also to allow control of how much stored water isheated. Another aim is to maintain condensing mode if required, orotherwise to prevent boiler circuit temperatures from falling to low.

The GX uses a thermostatic blender valve to maintain a set tempera-

ture for water pumped to the boiler for heating. For condensingboilers this is typically set between 45°C and 55°C. The flow ratethrough the boiler is then adjusted using the pump speed, or a bal-ancing valve, to obtain a roughly 20°C to 25°C rise through the boil-er at full output, resulting in a steady boiler output temperature ofaround 65°C to 75°C.

The return temperature, as set by the blender valve, can be finetuned to get the output temperature from the boiler just below thepoint where the boiler starts modulating or cycling.

This full temperature water is fed back into the top of the store, andgradually moves down until it reaches a cylinder thermostat, whenrecovery is stopped.

The use of more than one thermostat allows control over how muchwater is heated. For example, selecting to use a cylinder thermostatat the top of the store will result in only the top of the store beingheated. Likewise, using a thermostat near the bottom will result inall the store being heated.

Buffered Control of Boiler.

To further improve operation of boiler the use of seperate on/offcylinder thermostats is usually employed. The on thermostat ispositioned typically a third to a half way up the store and will tell theboiler to fire when the stored water has dropped to its set tempera-ture, typically 55°C to 65°C. As a result the boiler is never asked to

fire until there is a large volume of water to be heated. The offthermostat is positioned lower down the store and turns the boileroff once the volume of water between the two thermostats has beenheated.

This method of control avoides boiler cycling and modulating due tolow loads, with longer, less frequent burns, and for non-modulatingboilers and biomass boilers can be very important. Indeed, somebiomass boilers have a minimum burn time and as such demand abuffered control.

Connection to low output Stove or Burner.

One of the simplest methods of providing heat for hot water andheating is using a wood burning fire, gas stove or similar biomassburner. The heat provided is generally low output and can be trans-ferred to the GX store using gravity circulation, without the need fora pump.

For gravity circulation (thermo-syphon) to work, the water to beheated should be higher thanthe heat source. Therefore itworks better when the store ison a floor above the burner. Ifit is on the same level thensome transfer will happen, buta pump may need to be con-sidered. Without a pump,pipework is make in 28mm orlarger to minimise resistance.

With biomass being such animportant alternative fuel, aburner connecting to the storethis way provides a simle andeffective way to backup otherheat sources during coldweather and can often remove the need for a gas or oil boiler asbackup.

Connection to Solar Thermal.

Free energy from the sun is a very attractive proposition, especiallywhen you consider systems can pay for themselves in 5-10 years,and can generate 60% of a household’s hot water.

The GX range also allows energy from solar panels to be used forcentral heating, or more commonly underfloor heating. Central heat-ing circuits, or other heat dump, can automatically kick in to protectsystems from excess heat generated from the solar.

There are two methods of connecting panels to the GX. The first isthe standard method of using a coil. The solar panels and coil con-

tain water with anti-freeze. This is circulated by a pump when the

panels are hotter than the store. An expansion vessel caters forexpansion of the water, with a pressure relief valve for protectionagainst over-pressure or filling.

The second method of connection is more simple, using a direct flow

and return of store water to the panels. The panels will always befilled as they are below the water level in the feed and expansiontank. As there is no glycol, frost protection needs to be provided bythe solar controller running the pump when the panels approachfreezing. If the panels are higher than the feed tank then they willstill be filled by the pump pressure, but can also be drained of waterto protect against freezing.

Connection to (Renewable) Electric.

Electric heating elements provide a standard method of generatingheat. They provide a great deal of control, and have no problemachieving high temperatures without any loss of efficiency. Nearlyall GX systems have at least a single 3kW heating element for back-up, with options for up to 30kW.

The key to the use of electricity is the source. It is easy obtainingrenewable suppliers, with electricity generated mainly from hydro-electric and wind, however the cost of using electricty can be veryprohibitive unless a favourable tariff can be obtained, and this oftendepends on location.

Peak rate electricity typically costs more than twice that of off-peak.The problem is obtaining enoughhours of off peak supply to allow aproperty to be heated all day usingthis off-peak. Tariffs such asEconomy 7 provide overnight cheaprate electricity which is ideal forheating up water for domestic use attaps. However during the day, whencentral heating is needed, all supplyis at peak rate.

The GX can be used to store heatgenerated using a cheap rate tariff for providing both hot water andcentral heating. Additional storage is required for central heating,and the longer the periods without cheap rate power available, thelarger the store required. For every kilowatt-hour (kWh or unit) ofcentral heating one needs 20 litres of stored water. As the size ofstore gets smaller, then more often boosting with peak-rate willbecome neccessary, and running costs will rise. The aim when select-

ing tariffs is to find one with the stortest gaps between economyperiods, and one that is renewable.

The GX can be optionally fitted with a pre-wired 15kW heater con-troller, suitable for any tariff setup, with a remote manual boost facil-ity to bring on peak-rate supply when needed.

Connection to Heat Pumps.

A more efficient way to utilise electricity that standard heating ele-ments is to use a heat pump. These act like a refridgerator inreverse, using electricity to pump heat from either the ground or theair to be used for heating. They can increase the efficiency by typi-cally 400%, and can therefore be very effective in reducing electricalconsumption and costs.

Connection to Heat Pumps is made by either direct connections orusing a coil, depending on the make of heat pump.

Ground Source Heat Pumps with Solar Thermal.

Where solar thermal panel installations are oversized for just hotwater provision, with the aim of providing some central heating,there is usually a need to dump the excess heat generated by thepanels in summer months when there is no heating. When a GroundSource Heat Pump is also used, in order to generate higher efficien-cy electrical heating, it becomes beneficial to use the same groundas a heat dump for the solar. This helps overcome problems oftenencountered where heat pumps have had a gradual cooling effect onthe ground year to year, reducing efficiency as time goes on. Anyheat dumped from solar panels into the ground will counter this andeventually contribute to heating.

Radiators and Underfloor Heating using Boiler with Alternative.

By feeding different heating circuits from different points down thestore one can control which heating circuits are fed from the boiler.Circuits fed from the lower half of the store will only be heated usingthe boiler if a thermostat in the lower section of the store is beingused for boiler control.

This is most useful where there is a combination of radiators andunderfloor heating and an alternative heat source such as solar pan-els or heat pump. The radiator circuit is fed from the top half of the

store, with the underfloor from the lower half. Solar panel output isfed into the lower half of the store and can be used to provideunderfloor heating at lower temperatures, while the boiler is used toheat only the upper half of the store to feed radiators and generatemains hot water. In times when solar input is low the system caneasily switch to heat the entire store using the boiler thereby back-ing up the underfloor heating.

Level of Finish.

Our philosophy when building pre-fabricated systems is simply to doas much plumbing, wiring, testing and labelling as we can, ready fora quick and simple installation.

This approach can reduce installation times from days to hours, andprovides a standard documented design for the entire system.

Having the system fulled pre-assembled, wired and tested, with on-site backup, provides peace of mind that the design is sound, andany problems will be quickly resolved.

Five Minutes to Obtain a Design.

We have spent a number of years improving the means by whichcustomers can obtain detailed and sometimes bespoke designs tosuit their properties.

The PANEX System Designer on our web site allows one to quicklyanswer some basic questions and arrive at full colour, six pageinstallation and wiring details for a suitable pre-fabricated system.

http://www.dpsheatweb.com

Our technical advisors talk customers through designs prior to finalspecification to ensure options best match the requirements, andalso to highlight to the customer any design implications that mayneed their attention. This is aided by the fact that both parties canuse the software to view changes in design as they are discussed.

Help screens and useful calculators are built in to further explainoptions and help select the right ones. A single unit code is generat-ed by the software that holds all the options selected.