How do air source heat pumps work?
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There are many types of air source heat pumps in existance as it is a well proven technology. Commonly used air source heat pumps are air conditioning units, some of these untis have the capability to heat but will not have been optimised to do this in very low ambient external temperatures.
More recently, air source heat pumps have been able to heat homes through the year with no back up system. These heat pumps utilise a well proven process
called the vapour compression cycle. This
the same process that it used in your home refrigerator but in reverse. Rather than cooling things down the system
heats things up.
The diagram below shows the important stages.
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The evaporator absorbs heat from outside using a
low boiling point refrigerant gas.
- This gas is the moved to a compressor where the
gas is put under immense pressure.
- Under pressure the gas starts to condense on the
condenser and the temperature sky rockets.
- The fluid then is moved through an expansion
vessel which causes the temperature to plummet and the process begins again.
The Mitsubishi Ecodan is a 'monoblock' system, this means that the process occurs entirely within the outdoor unit. Split systems transfer the refrigerant inside the building, this has sizeable benefits when the location of the heat pump is a significant distance from the building (>25 metres). The drawback of this method is that the quantities of refrigerant require split systems to have an annual service by a refrigeration engineer.
While the heat pump is upgrading the heat to useful temperatures the system moves this heat through another circuit of more convention plumbing pipes. These pipes are connected to a set of zone valves with a control system that decides whether to send this heat to the heating distribution circuit (such as the radiators or underfloor heating) or to the hot water cylinder. The arrangement of valves typically used at Intelligent Energy Solutions is called an S-plan arrangement.
Due to the varying heating flow temperature (due to weather compensation), the s-plan arrangement is configured to prioritise hot water. This means that when the hot water storage cylinder calls to be heated (often timed for overnight) the system temporarily switches off the heating.
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