ICE AIR ccHPWH Series, Installation And Maintenance Manual

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II. Working principle
This heat pump water heater gathers heat from the environment (refrigerant-to-air HXR), compresses refrigerant
vapor to a higher temperature, then heats the working fluid (domestic water or glycol depending on the
application) in the condenser section (refrigerant-to-water HXR). The condensed high pressure and warm fluid
is rapidly expanded through the EEV to introduce cold liquid into the evaporator (ambient air side) to be boiled
off and complete the circuit. A reversing valve is utilized during the defrost cycle.
The condenser with double-wall plate heat exchanger has a protective air gap between the refrigerant and the
water circuit to prevent the refrigerant from entering the potable water side should a leak occur. In addition, it
greatly reduces the difficulty of maintenance. Each heat exchanger is equipped with water side isolations valves
and unions, as well as internal electrical disconnects. If a single system fails, the maintenance can be completed
without affecting the operation of refrigeration circuits in the system.
The electronic expansion valve is installed upstream of the evaporator and downstream of the condenser. It is
used to throttle the medium-temperature and high-pressure refrigerant to the low-temperature and low-pressure
gas-liquid mixture. The EEV is digitally controlled to accurately meter the refrigerant flow and control the phase
change.
The EVI systems (enthalpy vapor injection) utilizes an EEV to tightly control head pressure and discharge
temperature by bypassing the condenser coil and injecting cool vapor into the suction side of the compressor..