Johnson Controls York YIA Series Wiring Diagram page 9

Field control modifications

FIG. 14 – MULTIPLE UNITS (TWO) – PARALLEL

OPERATION – INDIVIDUAL UNIT PUMPS

(COOLING APPLICATION ONLY)

MULTIPLE UNITS (TWO) – PARALLEL

OPERATION – INDIVIDUAL UNIT PUMPS

This piping arrangement is the same as Fig. 15, ex‑

cept that the chilled water pumps associated with each

evaporator are cycled ON and OFF with the unit. This

results in reduced chilled water flow rates whenever

a single unit can handle the cooling load. Because no

chilled water flows through the inoperative unit, the

mixed water temperature peculiar to using a single pump

is avoided. When one unit is cut-out by the sequence

control (Fig. 12) the temperature of the supply chilled

water does not change.

JOHNSON CONTROLS

EVAPORATOR

LD06829

EVAPORATOR

FIG. 15 – MULTIPLE UNITS (TWO) – PARALLEL

OPERATION – SINGLE CHILLED WATER

PUMP (COOLING APPLICATION ONLY)

MULTIPLE UNITS (TWO) – PARALLEL OPERATION

– SINGLE CHILLED WATER PUMP

For this piping arrangement, each chiller's water sensor

is located in its own leaving water nozzle. This produces

a constant "mixed" chilled water temperature when

both units are operating. When either unit is cycled off

by the sequence control (Fig. 12), mixed chilled water

tempera ture will rise as a result of uncooled return water

flowing through the inoperative unit. For individual unit

chilled water pump piping, refer to Fig. 14.

FORM 155.21-W2 (1209)

LD06830