York YD A, Operating & Maintenance, Page: 33 / 52

JOHNSON CONTROLS
33
SECTION 3 – SYSTEM COMPONENTS DESCRIPTION
FORM 160.69-O2
ISSUE DATE: 9/30/2020
3
While the chiller is running, the refrigerant level is nor-
mally controlled to the level setpoint. However, anytime
the vanes fully close (VMS closes), normal level control
is terminated, any refrigerant level setpoint pulldown in
effect is cancelled and the outputs to the level control
will be opposite that which is supplied to the vane motor
(i.e., when a close pulse is applied to the vane motor, an
open pulse is applied to the level control, etc.). When the
VMS opens, if the refrigerant level is less than the level
setpoint, a refrigerant level setpoint pulldown is initiated
as described above. Otherwise, the level is controlled to
the programmed setpoint.
Isolation of the refrigerant in this system
must be performed by a qualified service
technician.
OPTIONAL HOT GAS BYPASS
Hot gas bypass is optional and is used to eliminate
compressor surge during light load or high head op-
eration. The OptiView™ control panel will automati-
cally modulate the hot gas valve open and closed as
required. Adjustment of the hot gas control valve must
be performed by a qualified service technician follow-
ing the Hot Gas Set-up procedure.
Changes in chilled water flow will require
readjustment of the hot gas control to
insure proper operation.
OPTIVIEW™ CONTROL CENTER
The OptiView™ Control Center is factory-mounted,
wired and tested. The electronic panel automatically
controls the operation of the unit in meeting system
cooling requirements while minimizing energy usage.
For detailed information on the Control Center, refer to
SECTION 2 – SYSTEM OPERATING PROCEDURES
on page 23
of this manual.
(See SECTION 2 – SYSTEM OPERATING PROCE-
DURES on page 23
)