McQuay M4AC040A, Installation And Maintenance Manual

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Troubleshooting with Microprocessor
(Not Include Carel Controller)
Symptoms Possible Causes Remedial Action
1. PCB display ‘CO’
x
Compressor thermal relay tripped
x
Terminal loose
x
Reset the thermal relay and carefully
monitor unit operation when it is
restarted
x
Tighten terminal screws.
2. PCB display ‘PO’
x
Pump thermal relay tripped
x
Terminal loose
x
Reset the thermal relay and carefully
monitor unit operation when it is
restarted.
x
Tighten terminal screws
3. PCB display ‘FL’
x
Flow switch connection loose
x
Water volume too low
x
Wrong direction of water flow
x
Tighten terminal screws
x
Add water into the system
x
Interchange power input phase
4. PCB, display ‘HP’
x
Discharge pressure too high
x
Overcharge
x
Coil dirty
x
Condenser fan does not work
x
Expansion valve stuck in open
position
x
Reset the pressure switch and
observe the unit operation when it is
restarted
x
Contact local dealer
x
Clean the coil with chemical
detergent
x
Contact local dealer
x
Replace it
5. PCB display ‘LP’
x
Suction pressure too low
x
Undercharge
x
Gas leak
x
Water flow rate too low
x
Reset the pressure switch and
observe the unit operation when it is
restarting.
x
Contact local dealer
x
Contact local dealer
x
Adjusting the flow rate
6. PCB display ‘E3’
x
Antifreeze protection activated.
x
Water flow rate too low
x
Bubble in the heat exchanger
x
Check the temperature setting
x
Adjusting the flow rate
x
Increase the water volume
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