York YMAE - Four-Pipe Simultaneous Cooling and Heat Recovery

Four-pipe simultaneous cooling and heat recovery
Air source coils are not utilized during simultaneous heating and cooling mode other than defrost
mode. Low-pressure liquid refrigerant enters the cooling BPHE through solenoid valve SV2
and is fully evaporated and superheated by the energy absorbed from the chilled water loop.
Low-pressure superheated refrigerant vapor passes through the accumulator and enters the
compressor, where pressure and superheat are increased.
High-pressure superheated refrigerant vapor enters the heating BPHE where heat is rejected to
the hot water loop. The subcooled refrigerant flows from the heating BPHE to the receiver, then
to the EVI’s BPHE to be further subcooled. Simultaneously, a portion of the subcooled refrigerant
flow passes through the EVI’s EEV, the refrigerant flow is then evaporated and superheated in the
EVI’s BPHE, then returns to the compressor as a cool gas. Also happening parallel to this, the main
portion of the subcooled liquid refrigerant flow passes through the main EEV, significantly reducing
the pressure causing the cooling effect to occur in the BPHE before returning to compressor
through the accumulator starting the refrigerant cycle over.
The four-pipe heat pump can simultaneously provide both heating and cooling to different zones or
areas within a building.
Figure 4: Simultaneous heating and cooling
Control logic auto-balances cooling and heating within the YMAE four-pipe chiller allowing
independent and dynamic control of both hot and chilled water temperatures. Auto-balance logic
also maximizes the utilization of cooling with heat recovery to improve energy efficiency.
To avoid the unit frequently shutting off and turning on cycling and to ensure water temperature is
stable, the building system water volume needs to be above the recommended minimum value.
YMAE Air-Cooled Inverter Scroll Chiller and Heat Pump26