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YORK INTERNATIONAL
tion of Service manual, Form 160.49-M2.
While the chiller is shut down, the orifice will be in the
fully open position causing the sensed level to be ap-
proximately 0%. When the chiller is started, after the
vane motor end switch (VMS) opens when entering
SYSTEM RUN, if actual level is less than the level
setpoint, a linearly increasing ramp is applied to the
level setpoint. This ramp causes the setpoint to go from
the initial refrigerant level (approximately 0%) to the
programmed setpoint over a period of 15 minutes. While
this ramp is in effect,
PULLDN LEVEL = XXX%; SETP = XXX%; ACTUAL = XXX%
is
one of the scrolled messages under the
DISPLAY DATA
key. PULLDN LEVEL is the ramping setpoint that will
ramp up to the programmed setpoint SETP. SETP
is the level setpoint programmed by the service techni-
cian. ACTUAL is the present refrigerant level in the
condenser. After the 15 minute pulldown period has
elapsed, this message is replaced by
ACTUAL LEVEL = XXX%; LEVEL SETP = XXX%
.
If the actual level is greater than the setpoint when the
VMS opens, there is no pulldown period, it immediately
begins to control to the programmed setpoint.
While the chiller is running, the refrigerant level is nor-
mally controlled to the level setpoint. However, any-
time 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. Oth-
erwise, the level is controlled to the programmed set-
point.
If the refrigerant level sensor output ever goes to greater
than 4.4VDC, indicating a level greater than 100%,
WARNING-REFRIGERANT LEVEL OUT OF RANGE
is dis-
played and the level control actuator is driven open
until the level has decreased to a level within range.
When within range, the warning message is automati-
cally cleared and normal control is resumed.
OPTIONAL SERVICE ISOLATION VALVES
If your chiller is equipped with optional service isola-
tion valves on the discharge and liquid line, these valves
must remain open during operation. These valves are
used for isolating the refrigerant charge in either the
evaporator or condenser to allow service access to the
system. A refrigerant pump-out unit will be required to
isolate the refrigerant.
CAUTION: Isolation of the refrigerant in this sytem
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 hot gas control panel will automatically
modulate the hot gas valve open and closed as re-
quired. Adjustment of the hot gas control valve must
be performed by a qualified service technician follow-
ing the Hot Gas Set-up procedure.
NOTE: Changes in chilled water flow will require re-
adjsutment of the hot gas control to insure
proper operation.
MICROCOMPUTER CONTROL CENTER
(See Section 2)
The MicroComputer 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 of this manual.
SOLID STATE STARTER (Optional)
The Solid State Starter is a reduced voltage starter that
controls and maintains a constant current flow to the
motor during start-up. It is mounted on the chiller. Power
and control wiring between the starter and chiller are
factory installed. Available for 380-600 volts, the starter
enclosure is NEMA-1 with a hinged access door with
lock and key. Electrical lugs for incoming power wiring
are provided.
VARIABLE SPEED DRIVE (Optional)
A 460V 3-Ph 60/50Hz Variable Speed Drive can be
factory packaged with the chiller. It is designed to vary
the compressor motor speed and prerotation vane po-
sition by controlling the frequency and voltage of the
electrical power to the motor. Operational information
is contained in Form 160.00-O1. The control logic au-
tomatically adjusts motor speed and compressor
prerotation vane position for maximum part load effi-
ciency by analyzing information fed to it by sensors
located throughout the chiller.
