Thermal Stores: Heat Kept Rather Than Water Stored
A thermal store keeps a body of hot heating water and passes heat to your tap water as it flows through a coil.
A thermal store keeps a body of hot heating water and passes heat to your tap water as it flows through a coil. Because the stored water is never drunk, the store itself sits outside some of the rules that apply to unvented cylinders.
Why anyone fits one
It gives mains-pressure hot water without a pressurised drinking-water vessel, and it can accept heat from more than one source at the same time.
The trade-off
Standing heat loss is higher than a well-insulated modern cylinder, and blending valves must be set correctly or outlet temperature wanders.
Where they fit best
Homes combining a boiler with solar thermal or a solid fuel appliance, where several heat inputs need somewhere to go.
Points we check on a store
- Blending valve setting and outlet stability
- Coil condition and scaling in hard water
- Whether stratification is being destroyed by pump overrun
Who does the work
- Gas Safe registered engineers — registration 554328
- Worcester Bosch accredited installer
- John The Plumb Ltd, company registration 10026483
Talk through a thermal store
If you have inherited a store and it is behaving oddly, describe the symptoms and we will work out whether it is the blender, the coil or the controls.
Questions we get asked
Is a thermal store the same as a cylinder?
No. A cylinder stores the water you wash in; a store keeps heating water and heats your tap water instantly through a coil.
Do thermal stores need an annual service?
They benefit from one, though the safety requirements differ from an unvented cylinder.
Can a combi feed a thermal store?
It is unusual and rarely the best arrangement. A system or heat-only boiler is a better match.