3. Expansion valve
2. Condenser
1. Compressor
4. Evaporator
(Indoor unit plate heat exchanger)
(Outdoor unit air heat exchanger)
2 kW
Low temperature renewable heat
energy taken from the environment
3 kW
1 kW
Electrical energy
input
Heat energy output
4
The purpose of this installation manual is to instruct competent persons how to
safely and effi ciently install and commission the cylinder system. The target read-
ers of this manual are competent plumbers and/or refrigeration engineers who
have attended and passed the requisite Mitsubishi Electric product training and
have appropriate qualifi cations for installation of an unvented hot water cylinder
specifi c to their country.
Overview of the System
The Mitsubishi Electric Air to Water (ATW) for heat pump system with cylinder unit
consists of the following components; outdoor heat pump unit and indoor cylinder
unit incorporating the main controller.
How the Heat Pump Works
Space heating and DHW
Heat pumps take electric energy and low grade heat energy from the outdoor air
to heat refrigerant which in turn heats water for domestic use and space heating.
The effi ciency of a heat pump is known as the Coeffi cient of Performance or COP
this is the ratio of heat delivered to power consumed.
The operation of a heat pump is similar to a refrigerator in reverse. This process
is known as the vapour-compression cycle and the following is a more detailed
explanation.
The fi rst phase begins with the refrigerant being cold and low pressure.
1. The refrigerant within the circuit is compressed as it passes through the com-
pressor. It becomes a hot highly pressurised gas. The temperature also rises
typically to 60°C.
2. The hot refrigerant gas is then condensed as it passes across one side of a
plate heat exchanger. Heat from the refrigerant gas is transferred to the cooler
side (water side) of the heat exchanger. As the temperature of the refrigerant
decreases its state changes from a gas to a liquid.
3. Now as a cold liquid it still has a high pressure. To reduce the pressure the liq-
uid passes through an expansion valve. The pressure drops but the refrigerant
remains a cold liquid.
4. The fi nal 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 out-
side air is absorbed by the refrigerant.
It is only the refrigerant that passes through this cycle; the water is heated as it
travels through the plate heat exchanger. The heat energy from the refrigerant
passes through the plate heat exchanger to the cooler water which increases in
temperature. This heated water enters the primary circuit and is circulated and
used to serve the space heating system and DHW cylinder.
Introduction
2
(238 pages)
(18 pages)
(15 pages)
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