SECTION 9 - MAINTENANCE
JOHNSON CONTROLS
171
Form 201.28-NM1.1
Issue date: 08/06/2021
9
Table 26 -
Troubleshooting guide
Problem
Possible cause
Action
No display on control panel unit
will not run.
Supply to the Panel is missing.
High Voltage to the Chiller is missing.
Check 1FU, 2FU, 4FU, 5FU 17FU, or
19FU.
Check 2T or 10T Transformer.
Line Fuse is blown.
Check Fuses.
Chiller Control Board is defective.
Replace Chiller Control Board.
Display Board defective.
Replace Display Board.
Line fuse blows.
SCR Diode Module is defective.
Check SCR/Diode Module.
IBGT Module is defective.
Check IBGT Module.
VSD Logic Board is defective.
Replace VSD Logic Board.
SCR Trigger Board is defective.
Replace SCR Trigger Board.
Chiller fault:
Low ambient temperature
Ambient temperature is lower than
the programmed operating limit.
Check the programmed cutout and
determine if it is programmed correctly.
Ambient Sensor is defective.
Check the panel against the thermometer
reading of ambient temperature.
Chiller fault:
High ambient temperature
Ambient Temperature is above the
maximum operating limit.
Check outside air temperature.
Ambient Sensor is defective.
Check the Panel Display against
Thermometer reading of Ambient
Temperature at the sensor.
Chiller fault:
Low leaving chilled liquid
Leaving chilled liquid temperature drops
faster than the unit can unload.
Check for restricted flow.
Check for rapid flow changes.
Water loop is too small.
Flow is below minimum for chiller.
Chilled Water Sensor is defective.
Check Sensor against Temp. Gauge in
water line.
Check Sensor for intermittent operation.
Check Wiring for shorts or opens.
System fault:
Control voltage
System Fuse is blown.
Check respective system Fuse 20FU
or 21FU.
Note:
Always remove power to the chiller and ensure the DC Bus voltage has bled off.
