69
JOHNSON CONTROLS
FORM 150.68-ICOM1
ISSUE DATE: 10/15/2020
COMPETENT PERSONS TROUBLE SHOOTING GUIDE
PROBLEM POSSIBLE CAUSE ACTION
No display on panel - Unit will not
operate
Main supply to unit o Switch on main supply if safe to do so.
Emergency stop device o
Check if remote emergency stop device
is in the OFF position. Turn to ON
position if safe to do so.
No supply to -T1
Check fuses -F3 and -F6 and wiring to
-T1 and fuse -F1.
No 24 VAC supply to microprocessor
board.
Check wiring from -T1 to J14
microprocessor board.
No 24 VAC output from Transformer -T1. Change transformer -T1.
Short circuit in wiring to temperature
sensors or pressure transducers.
Unplug connections at microprocessor
board to isolate.
Defective microprocessor board or
display board.
Replace board after contacting Johnson
Controls Service.
FLOW SWITCH OPEN displayed
No liquid ow through the liquid heat
exchanger.
Ensure that liquid pumps are running.
Valves are correctly set and ow is
established.
Flow switch contacts are not made.
Check that the ow switch is functional
and is installed according to the
manufactures instructions.
NOTE: On some systems the pump
starter may be wired to the unit and
controlled to start by the unit.
Detective ow switch. Replace ow switch.
UNIT FAULT: LOW AMBIENT TEMP
displayed in either mode or
HIGH AMBIENT TEMP displayed in
heating mode
Ambient air temperature is lower than
the programmed operating limit or, in
heating mode, higher than the trip value.
(Refer to Operating Manual (Form
150.68-O2.EN.GB)
Use the OPER DATA key to display
the temperature and conrm that the
displayed value is correct. The warning
message should clear when the
ambient air temperature reaches the
programmed operating limit. Check that
the programmed settings are correct for
the options tted to the unit.
Measured temperature is incorrect.
Check sensor calibration, location and
wiring.
UNIT FAULT: LOW LIQUID TEMP
displayed
Improperly adjusted leaving chilled liquid
temperature cut-out (glycol only).
Re-program the leaving chilled liquid
temperature cut-out.
Control panel setpoint/range values
improperly programmed.
Re-adjust setpoint/range.
Chilled liquid ow too low. Increase chilled liquid ow.
Defective -BLCT sensor. (Check that the
sensor is properly installed in the bottom
of the well with a generous amount of
heat conductive compound).
Compare sensor against a reliable
temperature sensing device.
See the Sensor Calibration Charts.
UNIT FAULT: 115 VAC
UNDERVOLTAGE displayed
Poor mains supply voltage.
Check mains supply is stable and within
allowable limits.
Check for voltage dip on compressor
start.
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