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How A Heat Pump Works - Mitsubishi Electric Ecodan PUHZ-W50VHA-BS Homeowner's Manual

Air source heat pump
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How a heat pump works

The heat pump essentially works the same way as your refrigerator but in reverse.
The Ecodan® is hermetically sealed (no refrigeration piping involved) with R410A
refrigerant, the cycle it completes to produce heat is known as the vapour-
compression refrigeration cycle:
The first phase begins with the refrigerant being cold and low pressure.
The refrigerant within the circuit is
compressor. It becomes a hot highly pressurized gas. The temperature also
rises typically to 60°C
The refrigerant is then
condensed
changer. Having a cooler side to the heat exchanger it decreases the tem-
perature, so it changes the property of the refrigerant from a gas to a liquid.
Now a cold liquid it still has a high pressure. For
through an expansion valve. The pressure drops but it is still a cold liquid.
The final stage of the cycle is when the refrigerant passes into the evaporator
and evaporates. It is at this point when some of the free heat energy in the
outside air is absorbed by the refrigerant.
It is only the refrigerant that is being passed through this cycle; the water is heated
up by the plate heat exchanger. The cooler water extracts energy from the hotter
refrigeration cycle, the water heats up as it passes across the exchanger. This wa-
ter flows towards the heating system and hot water storage tank.
Sealed Ecodan® Unit
Outside Air
4 evaporates
Evaporator
4
compressed
as it passes through the
as it passes across a plate heat ex-
expansion
to occur it passes
1 compressed
compressor
Expansion
3 expansion
Boiling points:
The refrigerant used within the cycle
has a different boiling point to water,
which boils (turns from liquid to gas)
at 100°C. This is only true at atmos-
pheric pressure. When the pressure
increases so does the boiling tempera-
ture; decrease the pressure and boiling
temperature drops. Liquid turns to gas
at a lower temperature. The boiling
point changes when the pressure
changes. Refrigerants have different
properties to water and have much
lower boiling temperatures. During the
fourth stage of the cycle the outside
ambient temperature is much hotter
than the temperature of the refriger-
ant and will heat it.
Hot water for heat-
ing and hot water
2 condensed
Heat Exchanger

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