York YCSA 120 T Technical Information page 13

Cooling cycle
The 4-way valve is activated. Heat exchange takes place
between the heat transfer liquid (water or glycol water) and
the refrigerant in the plate heat exchanger. Water is cooled,
and refrigerant is evaporated and reheated. Then the Scroll
type compressor condenses the refrigerant (gas) until the
condensing pressure is reached, and the refrigerant goes to
the air cooled condensing unit. In the air cooled condensing
unit, heat is exchanged between the air and the refrigerant.
The air is heated and evacuated from the chiller (heat rejec-
tion). The refrigerant is condensed and sub-cooled. Then the
refrigerant (liquid) goes on to the expansion valve, where it
is expanded until the evaporating pressure is reached, at
which time it goes to the evaporating unit to end the cooling
cycle.
Heating cycle
The cycle is reverse to heating mode. The 4-way valve is not
activated. The condensing unit becomes the evaporating unit,
and the evaporating unit becomes the condensing unit. The
water in the plate heat exchanger is heated.
13