I am going to assume you already know how an Air Source Heat Pump (ASHP) works, or you have read our blog ‘What is a Heat Pump?’ (http://heatking.co.uk/blog/heat-pump/). If not please read our previous blog first to help you understand this one.
HeatKing has two models designed for domestic properties in Northern Europe that, for one reason or another, require a higher flow temperature than “normal” ASHPs can deliver efficiently.
These units (BWarm 9000i & 13000i) work in a very similar way to their sister range but have a more sophisticated compressor and an additional heat exchanger, as shown in the diagram below:-
I’ll start my explanation of the heat pump’s circuit by following the refrigerant as it leaves the compressor.
The high pressure/high temperature refrigerant gas leaves the compressor (1) and passes into a condenser (2) (plate heat exchanger) that has the heating system’s water passing through it (3). The heat from the hot gas is transferred across the condenser to the water returning from the heating system and is consequently heated. As the hot gas transfers it’s heat to the heating water it begins to cool and condenses back into a liquid.
This liquid leaves the heat exchanger through two pipes (4), one heading towards an expansion device (TEV) (5), which expands the liquid and makes the liquid very cold, while the other pipe leads directly into a subsequent heat exchanger (6). As with the previous heat exchanger the warm liquid (7) heats the cold liquid (8) making it boil (evaporate). It leaves the heat exchanger as a warm vapour (9) and re-enters the compressor at roughly half way through the compression cycle, thus enabling it to achieve higher temperatures. The liquid that has given up some of its heat (10) passes through another expansion valve (TEV) (11), which makes the liquid even colder (12), and then enters the evaporator (13) where it absorbs all that lovely free heat from the outside air. This free heat provides enough heat to boil (evaporate) the liquid back into a low pressure gas (14) which is then sucked into the compressor (15), it’s compressed and converted into a high pressure hot gas and the whole cycle begins again.
So with this very sophisticated process we are able to provide high temperature hot water at low ambient temperatures. For example, at an outside temperature of 0oC a BWarm 13000i will produce water at a temperature of 60oC and for every 1kW of electricity used the heat pump will supply 2.4kW of heat!