A buffer tank is a hot water storage tank that is well insulated having minimal thermal loss, is designed to smooth out any great temperature oscillations and to store heat for long after boiler shuts down.
Looking at a scenario where user using DWBi boiler, has filled the boiler with fuel and allowed the temperature to build. Assuming the first load of fuel was not quite enough for the property to reach desired temperature, user then topped up the boiler with more fuel.
Boiler was then left to run for approx. 20-30 minutes, long enough for a good size cherry to form inside the fire box. A desired house temperature was then achieved causing thermostats to shut off. This would cause the boiler to reach its pre set temperature a controller will then shut off oxygen supply to the fire in order to stop the cycle.
With the oxygen shut off, residual heat from the cherry still radiating is now causing temperature to build up, how much by, would be directly related to the size of cherry or more down to how much extra fuel was added during top up. This can cause temperature to increase by as much as 20 - 30 degrees C.
To harness this and to keep the temperature steady, a leak off radiator or a buffer tank is used. Buffer tank being more efficient solution of the two systems and it will even out any temperature changes so that a steady flow is maintained. If the boiler and buffer are well matched to the property size, temperature change is rarely more than +/- 8 degrees C. whilst maintaining good heat delivery for as long as for 18hrs during winter months from one load.
When sizing a tank many different variables are taken in to consideration and its best to give us a call so that equipment chosen performs to users satisfaction.