228
FORM 160.54-M1
ISSUE DATE: 10/25/2019
SECTION 26 - VARIABLE GEOMETRY DIFFUSER
JCI COMPANY CONFIDENTIAL
JOHNSON CONTROLS
of stall noise present. When it reaches the value
programmed as the High Limit setpoint (typically
set to 0.8 VDC), the VGD closes until the voltage
decreases to the Low Limit setpoint (typically set
to 0.6 VDC). Since the filter causes the STALL
DETECTOR VOLTAGE to typically run 0.2 to
0.3 VDC lower than Standard Mode for the same
condition, it may be necessary to lower the High
Limit and Low Limit setpoints if valid stall condi-
tions are not being detected or surge occurs before
stall is detected. Ideally, stall should be detected
before surge occurs, allowing the VGD to react
before surge. Also, since the PRV Position – VGD
Inhibit Setpoint was the original vehicle to avoid
VGD reaction to high gas flow/low head condi
-
tions, this setpoint should be set to 95% or 100%
to avoid interference when Enhanced Mode is se-
lected.
• STANDARD Mode – This mode should not be
used unless under the advisement of Johnson
Controls technical support. Provides the same
operation as the 031-02418-000 board. Does not
filter high gas flow/low head noise conditions as
described in enhanced mode above.
FIGURE 81 -
VARIABLE GEOMETRY DIFFUSER BLOCK DIAGRAM
LD09467b
VGD
ACTUATOR
NOTES:
1. Requires I/O Board 031-01743-002
Open
Close
3
2
1
158
159
160
TB1
I/O
BOARD
MICRO
BOARD
SEE NOTE 1
31
30
J1
23
24
31
30
12
J7
J8
J19
4
3
1
1
2
J2
STALL
DETECTOR
BOARD
STALL
TRANSDUCER
Open
STALL
DETECTOR
OUTPUT
STALL
TRANSDUCER
OUTPUT
GND
+5 Vdc
OUT
GND
+5 Vdc
Close
1
2
3
J1
3
1
2
J1
NOTE:
Requires I/O Board 031-01743-002
* Refer to PIN Connections above
*
*
*
