Table of Contents
Advertisement
The chiller can be provided with an optional Con dens er
Refrigerant Level Control. A Variable Orifi ce, lo cat ed
in the refrigerant liquid line between the Evap o ra tor and
Condenser, is used to control the re frig er ant level in the
Condenser. It is modulated by an Actuator that is driven
by open and close output sig nals from Triacs on the I/O
Board. These control sig nals orig i nate at the Microboard.
Automatic or Manual lev el con trol is allowed. If Auto-
matic control is se lect ed, the Pro gram modulates the
Variable Orifi ce to maintain the Condenser refrigerant
to a programmable Setpoint lev el. If Manual control is
selected, the Variable Orifi ce can be manually controlled
with the Keypad keys. This Manual control can also be
used to place the Orifi ce in a fi xed position.
Since the Level Control feature is optional, the Pro-
gram operation described here must be ENABLED on
those chillers so equipped and DISABLED on all oth er
chill ers. This procedure, along with the pro gram ming of
Setpoints described below, is performed on the Re frig -
er ant Level Control/Tuning Screen using in struc tions
in the "System Calibration, Service Setpoints and Reset
Procedures Programming Procedures" section of this
book.
A Liquid Level Sensor (LLS) detects the Refrigerant
Level in the condenser and outputs an analog voltage
to the Microboard that rep re sents this level. The level
is expressed as a percentage and is displayed on the
Condenser Screen and the Refrigerant Level Control
Screen as the "Re frig er ant Level Position = xxx%". The
Level Sensor is calibrated so that the re frig er ant level is
displayed as 0% when the level is at minimum; 100%
when the lev el is at maximum. Levels between these
extremes are linearly scaled. The lev el is at min i mum
when the when the chiller is shutdown with the orifi ce
in the fully open position. The level is at max i mum
when the level is above the site glass, with the sensor
fully covered. The Level Sensor analog output voltage
is rescaled by the Microboard. This rescaled voltage is
viewable as input 23 on the ANALOG I/O Diagnostic
Screen and is the voltage value that is used for the cali-
bration of the Level Sensor. The level will be displayed
as 0% when input 23 on the ANALOG I/O Diagnostic
Screen is 0.37VDC and 100% when it is 4.31VDC. The
Level Sensor is calibrated to output val ues that would
produce these levels on the AN A LOG I/O Diagnostic
Screen.
The desired refrigerant level to be maintained in the
YORK INTERNATIONAL
SECTION 14
REFRIGERANT LEVEL CONTROL
(REFER TO FIG. 51 & 52)
con dens er is the Refrigerant Level Setpoint and is
dis played as "Re frig er ant Lev el Setpoint = xxx%" on
the Condenser Screen and the Refrigerant level Con trol
Screen.
This Setpoint is pro grammed by a Service Technician at
chiller com mis sion ing using the Refrigerant Level Con-
trol Screen. It is pro gram ma ble over the range of 20% to
80%.
AUTOMATIC OPERATION
While the chiller is shut down, an Open signal is ap plied to
the Actuator, driving the Orifi ce to the fully open po si tion.
This causes the Condenser refrigerant level to be ap prox i-
mate ly 0%. Elevated Evaporator pres sure with respect to
Condenser pressure could cause the lev el to be higher.
When a chiller start is initiated, there are two different
courses of action taken, depending on the Flash Memory
Card version as follows:
If equipped with Flash Memory Card version
C.MLM.01.06.xxx and earlier or "P" compressors
with C.MLM.04.02.xxx and earlier: After the chiller
is started, when the Vane Motor Switch (VMS) opens
after entering SYSTEM RUN, if the ac tu al level is
greater than the Level Setpoint, the Microboard begins
controlling the level to the Level Setpoint. How ev er, if
the actual level is less than the Level Setpoint, a linearly
increasing ramp is applied to the Level Setpoint. This
ramp causes the Setpoint to in crease from the ini tial
refrigerant level to the pro grammed Level Setpoint over
a period of 15 minutes. While this ramp is in ef fect, the
ramp value is dis played as "REFRIGERANT LEVEL
TAR GET = XX%" and replaces the Level Setpoint mes-
sage on the Con dens er Screen. While the ramp is in
effect, "RAMP UP TIME RE MAIN ING = XX MIN" is
dis played. Af ter the 15 minute ramp period has elapsed,
the re frig er ant level is con trolled to the pro grammed
Level Setpoint.
If equipped with Flash Memory Card version
C.MLM.01.07.xxx and later: Upon entering chiller
Prelube, the Refrigerant Level close output is ener-
gized for the length of the programmable Valve Preset
Time Setpoint (0 to 100 seconds; default 50). After
pre-positioning, the valve is held in this position until
the fi rst 3 minutes of Chiller Run Time has elapsed
(Setting the Valve Preset Time to 0 seconds disables
FORM 160.54-M1(503)
14
91
Advertisement
Table of Contents
