A thermal store cylinder works in the opposite way to an indirect cylinder.
Indirect cylinders have a coil filled by heated water from the boiler / heat source, this heated coil heats the water in the main body of the cylinder and this water is used to provide domestic hot water.
The domestic hot water can be provided using an open vented design,with open vented systems a large volume of cold water is stored in a header tank located at a higher level than the cylinder usually in the attic. The indirect cylinder is fed at the base of the cylinder by the water from the header tank which is pushed out of the top of the cylinder to the taps and showers. The system is driven by gravity, i.e. the static head of stored water in the header tank. This type of set up results in low water pressure meaning poor showers, unless expensive shower pumps are used to boost the shower pressure.
The other option is an unvented hot water cylinder, this gets over the problem of the poor pressure on the hot water supply as it is supplied by the water main (normally with the pressure restricted to 3 bar) but these cylinders require a specialist installer and yearly inspections. The main disadvantagesof indirect cylinders are:-
Hot water availability is restricted by the heat recovery time period and size of cylinder.
Tanks in the attic, risk of freezing.
Additional coils are required if you wish to heat the hot water from more than one heat source and it gets even more complicated if you also want the other heat source to contribute to the heating load as this will involve a complicated piping arrangement involving non return valves as well as the additional pipework, fittings and labour cost.
Thermal Store Cylinders
In a thermal storage system, it is the water in the cylinder which is heated by the boiler / heat source(s), then stored and maintained at a constant temperature. The water for taps and showers comes from the mains supply meaning it is fresh and clean, it enters a series of highly efficient coils within the cylinder which transfer the heat from the hot water stored in the cylinder it then goes on to the taps and showers - still at mains pressure (normally restricted to 3 bar). There are numerous advantages of using a thermal store:-
Mains pressure hot water means fast filling baths and really powerful showers.
The boiler will operate at close to peak efficiency. With the exceptionally high insulation levels of the thermal store ensuring that the water temperature rarely drops more than 10-15°C, the demands on the boiler are such that stop/start cycles are greatly reduced, producing savings in running costs The standing loss of our 280 lit. thermal store is only 2.7kw/hr over a 24 hour period.
The primary water in the thermal store is always available for instant supply to heating and hot water at optimum temperature I.e. no heat up time.
Recovery is fast and is totally dependant on the output of the boiler(s) and is not restricted by coils as the heat is directly fed into the cylinder mass.
Controls are simplified as hot water programming is no longer necessary.
The thermal store does not fall under the same regulations as unvented hot water cylinders, due to the stored domestic hot water being contained within the coils and having a volume under 15 litres, meaning thermal stores do not require the same specialist installation or yearly inspections that unvented indirect cylinders do.
There is a considerable saving in pipework as you only require a flow and return pipe from the boiler/ heat source to the cylinder as both the hot water and heating is piped from the cylinder and no additional tees, zone valves etc are required to provide independent heating / hot water.
Our cylinders are supplied solar ready, the solar will contribute to the heating and hot water and you can even add a towel rail circuit which can use the excess heat provided by solar in warm weather conditions. The solar can be installed at the time of installing the cylinder or if you decide to install solar at a later date it can simply be connected to the cylinder at that time, avoiding the need to change your cylinder to accommodate solar.
Additional heat sources are easily added to the thermalstore, extra connections can be supplied on the cylinder to accept the flow and return of an additional heat source, connection is easy and a contribution is made to the heating / hot water load.
The heating water in the thermalstore is like most heating systems and is usually installed as a closed system fitted with an expansion vessel. However if required it will work just as well with an open vented system with a feed and expansion tank. This type of system is required if your additional heating source is an AGA Cooker, wood burning stove, back boiler etc. so there are no problems connecting this type of system to our thermalstore cylinder, an open vent system on the heating side will not effect the hot water system which will still deliver clean fresh hot water at mains pressure (up to 3 bar).
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