JOHNSON CONTROLS
8
FORM 155.21-W2 (1209)
MULTIPLE UNITS (TWO) ‑ SERIES OPERATION
The supply chilled water temperature to the building is
normally determined by the chilled liquid temperature
setpoint for Unit #2. When lead selector position of se
‑
quence control kit (
Fig
. 12) is Unit #1, the supply chilled
water temperature to the building will be the temperature
control setpoint on Unit #1 OptiView™ Control Center.
if lower temperature is desired, reprogram the chilled
liquid temperature setpoint for Unit #1.
LD06826
FIG. 13 –
MULTIPLE UNITS (TWO) – SERIES OPERATION (NOTES 8 & 11)
TWO UNIT SEQUENCE CONTROL
Provides that cycling thermostat RWT will automatically
cycle either #1 or #2 unit. Timer 3TR is an additional
feature which prevents simultaneous starting of lead
and lag unit following a power failure and eliminates
nuisance starting of lag unit due to periodic fluctuations
in temperature. For two unit sequence control kit, order
YORK Accessory Kit No. 466-61597T for controls as
specified with NEMA 1 enclosure.
RWT has 20°F to 80°F range with adjustable differential
of 3-1/2 to 14°F; 6 ft. of capillary with 3/8" x 5" bulb and
1/2" NPT brass well (maximum liquid DWP 300 PSIG
).
The thermostat is drawn to indicate its operation closes
on rise. A 1/2" pipe coupling in the return chilled water
line from the building must be furnished (by others) for
RWT control well.
EVAPORATOR
EVAPORATOR
LD06835
FIG. 12 –
TWO UNIT SEQUENCE CONTROL (COOLING APPLICATIONS ONLY)
