What is the difference between a thermal store and a buffer tank?
What is the difference between a thermal store and a buffer tank? A thermal store and a buffer tank are two insulated vessels that store heated water, but they serve very different purposes within a heating system.
Buffer tanks
A buffer tank is essentially useful for improving the performance of a space-heating or cooling system. It increases the overall volume of water in the system, giving it more thermal mass. This is especially useful with heat pumps, biomass boilers and other heat generators that work better when they can run for a bit and not just switch on and off all the time.
By storing surplus heat temporarily, a buffer tank can reduce short cycling, improve temperature stability and help maintain the minimum system water volume required by the heat-source manufacturer. Depending on its connection arrangement, it may also provide hydraulic separation between the heat-source circuit and the heating distribution circuit. This allows different pumps and flow rates to operate without interfering with one another. Our general range of buffer tanks is detailed here Buffer tanks or our range of buffer tanks for heat pumps, are detailed here Buffer tanks for heat pumps
A buffer tank normally contains the same primary heating water that circulates through radiators, underfloor heating or fan-assisted heating units. It does not usually produce domestic hot water for taps, showers or baths.
Thermal stores
A thermal store, on the other hand, is basically designed to store a lot more thermal energy and distribute it to a number of different services. It might obtain its heat from one or more sources – say a gas boiler, an oil boiler, a biomass boiler, a heat pump, solar thermal, a solid-fuel appliance or an electric immersion heater.
The stored water in a thermal store is normally the primary heating water. Domestic hot water is then produced indirectly, either through an internal heat-exchanger coil or an external plate heat exchanger. This means the stored water itself does not normally come from the taps. Instead, incoming mains water is heated as it passes through the heat exchanger, providing hot water without storing a large volume of heated potable water.
Our full range of thermal store domestic hot water cylinders are detailed here – Thermal store cylinders
A thermal store might also feed radiators or underfloor heating and act as a kind of central energy-management hub for multiple heat sources. Keeping the water in the store stratified – with the hotter water at the top and the cooler water at the bottom – is pretty important.
Conclusion
Thus the main difference is the purpose of each: a buffer tank supports the efficient and stable operation of the heating or cooling system, while a thermal store is all about storing and managing energy for space heating and possibly producing domestic hot water.
However, the terms are sometimes used interchangeably because some vessels can perform both duties. The correct choice depends on the required system volume, heat-source output, domestic hot-water demand, hydraulic arrangement and control strategy.
