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SECTION 2 - SYSTEM ARCHITECTURE
FORM 160.54-M1
ISSUE DATE: 10/25/2019
JOHNSON CONTROLS
JCI COMPANY CONFIDENTIAL
2
Stall noise is detected as gas pressure pulsations. A
stall pressure transducer, mounted in the discharge
scroll of the compressor, detects the gas pressure pul-
sations and outputs DC voltage pulsations to the
s
tall
detector board, which converts the voltage pulsations
into an analog voltage that represents the magnitude
of the stall noise. This analog voltage is input to the
microboard where it is compared to thresholds that de-
termine if the stall noise is acceptable or unacceptable.
The VGD is pulsed toward the closed position in re-
sponse to unacceptable stall noise. Otherwise, it is
modulated to maintain the most open position pos-
sible without stall occurring. Software version
C.MLM.01.10.xxx (and later) or C.OPT.01.10.302
(and later) and I/O board 031-01743-002 is required
for this feature. A pre-rotation vanes position potenti-
ometer is also required to support this feature.
If the chiller is provided with a compressor motor VSD
or the optional hot gas bypass, the PRV potentiometer
for those features is used. Otherwise, a PRV potenti-
ometer is provided interfaced to the microboard.
After July 2009, chillers that are equipped for the hot
gas bypass, heat recovery or head pressure control op-
tions are equipped with a Large Tonnage Chiller (LTC)
I/O board. This board provides for analog and digital
inputs and outputs for these features and it communi-
cates with microboard (P/N 031-02430-00/001 COM3
RS-485 serial port using Modbus protocol.
After February 2010, chillers can be equipped with
an optional motor monitoring feature. Motor winding
temperature sensors and bearing temperature and vi-
bration sensors are interfaced to the motor monitoring
board (located in a separate box). The motor monitoring
board communicates the winding and bearing tempera-
tures and bearing vibration values to microboard (P/N
031-02430-000/001 COM3 RS-485) serial port using
Modbus protocol. These parameters are displayed.
Warning messages are displayed and safety shutdowns
occur in response to high temperature and vibration
conditions. Software version C.OPT.01.22.307 (and
later) is required for this feature.