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FORM 160.54-M1
ISSUE DATE: 10/25/2019
SECTION 17 - REFRIGERANT LEVEL CONTROL
The chiller can be provided with an optional Condenser
Refrigerant Level Control. A Variable Orifice, located
in the refrigerant liquid line between the Evaporator
and Condenser, is used to control the refrigerant level
in the Condenser. It is modulated by an Actuator that
is driven by open and close output signals from Triacs
on the I/O Board. These control signals originate at the
microboard. Automatic or Manual level control is al-
lowed. If Automatic control is selected, the Program
modulates the Variable Orifice to maintain the Con-
denser refrigerant to a programmable setpoint level. If
Manual control is selected, the Variable Orifice can be
manually controlled with the keypad keys. This Man-
ual control can also be used to place the Orifice in a
fixed 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 other
chillers. This procedure, along with the programming
of setpoints described below, is performed on the RE-
FRIGERANT LEVEL CONTROL/TUNING Screen
using instructions in SECTION 33 - SYSTEM CALI-
BRATION, SERVICE SETPOINTS, AND RESET PRO-
CEDURES of this manual.
A Liquid Level Sensor (LLS) detects the Refrigerant
Level in the condenser and outputs an analog volt-
age to the microboard that represents this level. The
level is expressed as a percentage and is displayed on
the CONDENSER Screen and the REFRIGERANT
LEVEL CONTROL Screen as the REFRIGERANT
LEVEL POSITION = XXX%. The Level Sensor is cal-
ibrated so that the refrigerant level is displayed as 0%
when the level is at minimum; 100% when the level is
at maximum. Levels between these extremes are lin-
early scaled. The level is at minimum when the chiller
is shutdown with the orifice in the fully open position.
The level is at maximum when the level is above the
site glass, with the sensor fully covered.
The Level Sensor calibration procedure is in SECTION
33 - SYSTEM CALIBRATION, SERVICE SETPOINTS,
AND RESET PROCEDURES of this manual. There
are different versions of the Level Sensors as shown in
Figure 71 on page 164. The operation of the sensors
is the same. However, the differences affect the way the
sensors are calibrated. Some sensors are equipped with
adjustable potentiometers, while others are equipped
with pushbuttons that are used to calibrate the sensor.
JOHNSON CONTROLS
The desired refrigerant level to be maintained in the
condenser is the Refrigerant Level setpoint and is
displayed as REFRIGERANT LEVEL SETPOINT
= XXX% on the CONDENSER Screen and the RE-
FRIGERANT LEVEL CONTROL Screen.
This setpoint is programmed by a Service technician
at chiller commissioning using the REFRIGERANT
LEVEL CONTROL Screen. It is programmable 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 Orifice to the fully
open position. This causes the Condenser Refrigerant
Level to be approximately 0%. Elevated Evaporator
Pressure with respect to Condenser Pressure could
cause the level to be higher.
When a chiller start is initiated, there are two different
courses of action taken, depending on the Flash mem-
ory card version as follows:
1. 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 actual level is greater than the Level setpoint,
the microboard begins controlling the level to the
Level setpoint. However, 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 increase from the initial refriger-
ant level to the programmed Level setpoint over a
period of 15 minutes. While this ramp is in effect,
the ramp value is displayed as REFRIGERANT
LEVEL TARGET = XX% and replaces the Level
setpoint message on the CONDENSER Screen.
While the ramp is in effect, RAMP UP TIME
REMAINING = XX MIN is displayed. After the
15 minute ramp period has elapsed, the refriger-
ant level is controlled to the programmed Level
setpoint.
2. If equipped with Flash memory card version
C.MLM.01.07.xxx (and later).
Upon entering chiller Pre-lube, the Refrigerant
Level close output is energized for the length of
JCI COMPANY CONFIDENTIAL
17
165
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