Buffer Tanks in Heating
The word buffer means to reduce impact, to do this it absorbs energy or momentum then is able to give it back. The energy is usually excess to the immediate requirements but will be needed in the near future so the storage is short term.
The buffer tank in a heating system is used to smooth out the difference between the supply and demand. With a multi zone heating system this is constantly changing. In most domestic gas/oil installations the boiler can modulate within the design range of the heating distribution and therefore it is possible to get away without fitting a buffer.
|Air Source Heat Pumps and Buffers|
Air source heat pumps require defrosting when the outside temperature falls close to zero and the moisture in the air forms ice on the fins. During defrost the fins are heated by reversing the heat pump. Reversing the system means taking heat from the heating water, thus cooling it and transferring it to the fins using the refrigeration principle. If there is insufficient heat in the water, the defrost may not be efficient and take a long time. The heating water will cool down as it passes through the heat pump and if insufficient water to draw on it will cool the heating circuit.
If the heating circuit is not circulating enough water the defrost will fail. A failed defrost means capacity loss due to the fins blocking with ice.
There must be enough water in the system excluding the heating circuit to defrost. This is achieved by installing a buffer tank in the return line to the heat pump.