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Form 201.28-NM1.1
Issue date: 08/06/2021
Table 26 - Troubleshooting guide
Problem
No display on control panel unit
will not run.
Line fuse blows.
Chiller fault:
Low ambient temperature
Chiller fault:
High ambient temperature
Chiller fault:
Low leaving chilled liquid
System fault:
Control voltage
Note: Always remove power to the chiller and ensure the DC Bus voltage has bled off.
JOHNSON CONTROLS
Possible cause
Supply to the Panel is missing.
Line Fuse is blown.
Chiller Control Board is defective.
Display Board defective.
SCR Diode Module is defective.
IBGT Module is defective.
VSD Logic Board is defective.
SCR Trigger Board is defective.
Ambient temperature is lower than
the programmed operating limit.
Ambient Sensor is defective.
Ambient Temperature is above the
maximum operating limit.
Ambient Sensor is defective.
Leaving chilled liquid temperature drops
faster than the unit can unload.
Chilled Water Sensor is defective.
System Fuse is blown.
SECTION 9 - MAINTENANCE
Action
High Voltage to the Chiller is missing.
Check 1FU, 2FU, 4FU, 5FU 17FU, or
19FU.
Check 2T or 10T Transformer.
Check Fuses.
Replace Chiller Control Board.
Replace Display Board.
Check SCR/Diode Module.
Check IBGT Module.
Replace VSD Logic Board.
Replace SCR Trigger Board.
Check the programmed cutout and
determine if it is programmed correctly.
Check the panel against the thermometer
reading of ambient temperature.
Check outside air temperature.
Check the Panel Display against
Thermometer reading of Ambient
Temperature at the sensor.
Check for restricted flow.
Check for rapid flow changes.
Water loop is too small.
Flow is below minimum for chiller.
Check Sensor against Temp. Gauge in
water line.
Check Sensor for intermittent operation.
Check Wiring for shorts or opens.
Check respective system Fuse 20FU
or 21FU.
9
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