Introduction

Operating to similar but reversed principle to a vented gravity fed system, a thermal store cylinder is filled with hot water directly from the hot water boiler, and the heat exchanger carries water to and from the taps.

Water supply

The advantage to the thermal store principle is that the water supplying the taps can be supplied directly from the mains, rather than a cold water storage (header) tank in the loft, thus allowing hot water to supply the entire property at mains pressure.

The ability to supply hot water at mains pressures is a real plus if you enjoy a powerful shower, however it's worth noting that this form of hot water supply cannot be used in conjunction with standard power showers, and water pumps.

• Shower options

As with standard vented cylinders, thermal store cylinders also require a seperate cold water tank to provide venting for expansion of the hot water, however unlike standard cylinders this cold water tank does not need to be very large as it does not supply cold water to the property.

Combined thermal store cylinders

Thermal store cylinders are frequently available in a combined unit with the cold water ventillation tank, this makes them a great space saving option, particularly if used in a property with limited or no loft space.

However, the water from the boiler that feeds the main hot water tank, also feeds the radiators within the heating system, and it does so using a gravity feed, or 'head' of water.

With this in mind, a combined unit thermal store cylinder must be located above the level of the highest radiators in the property, ie upstairs rather than in a basement.

If this not practical, single cylinder thermal store vessels are available, which are vented to a seperate small cold water tank in the loft space. This drop of water provides the head of water pressure to adequately feed all the radiators in a property.

Pros & cons

Further information and useful links

• Find a Heating Engineer near you
• Find a Plumbing Merchants near you