York YLPA 0115SE, Installation, Operation And Maintenance Manual

Page: 14 / 90

14
JOHNSON CONTROLS
FORM 150.68-ICOM1
ISSUE DATE: 10/15/2020
REFRIGERANT FLOW BLOCK DIAGRAMS
Cooling and Defrost Modes
Low pressure liquid refrigerant enters the heat exchanger and is evaporated and superheated by the heat energy
absorbed from the chilled liquid. Low pressure vapor enters the compressor, via the four-way reversing valve and
accumulator, where pressure and superheat are increased. The high pressure vapor is fed to the ambient coils and
fans, via the four way reversing valve, where heat is removed. The fully condensed and subcooled liquid passes
through the electronic expansion valve where pressure is reduced and further cooling takes place before returning
to the heat exchanger.
Heat Pump Mode
Liquid refrigerant enters the ambient coil, and is fully evaporated and superheated by the energy absorbed from the
ambient air. Low-pressure superheated refrigerant vapor passes through the four-way reversing valve and the
accumulator and enters the compressor, where pressure and superheat are increased. High-pressure superheated
refrigerant vapor enters the refrigerant to water plate heat exchanger where heat is rejected to the water. The high-
pressure liquid refrigerant, leaving the heat exchanger passes through the liquid receiver and enters the electronic
expansion valve where the refrigerant pressure is reduced and subsequently cooled before returning to the ambient
coil.
Defrost
When ice builds up on the ambient coils defrost is initiated by operating the machine in a cooling mode. Each of
the refrigerant circuits will be defrosted one at a time. When defrost is operative the circuit operating in heat pump
mode is in balance with the circuit operating in defrost (cooling). Therefore, heat energy is not removed from the
hot water system.
Ambient Coils
(Condenser)
Refrigerant flow
Compressors
Heat Exchanger
(Evaporator)
4-way valve
Accumulator
Receiver
EEV
Ambient Coils
(Evaporator)
Refrigerant flow
Compressors
4-way valve
Accumulator
Receiver
Heat Exchanger
(Condenser)
EEV