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14
Alarm/Fault Reason Action(s)
High Discharge Pressure / HP/
HD Switch Alarm
Dirty condenser coil Clean coil with water
Condenser fan malfunction
Check fan coil and replace if necessary
Ensure fan spins freely
Measure motor amperage and ensure it is not higher than
nameplate
Refrigerant overcharged
Remove excess refrigerant; the high pressure in the
control should be between 2.3 to 2.8 MPa
Expansion valve is set too
“loose”
Appropriately adjust the opening degree of the expansion
valve
Expansion valve failure Replace expansion valve
Contaminated refrigerant
Check the sight glass for refrigerant quality and level
Replace refrigerant if necessary
Not enough airflow Ensure proper airflow clearances
Condenser signal wiring
disconnected
Ensure condenser signal wiring is still intact
Low Suction Pressure
Low heat load (minimum
cooling capacity exceeds the
heat load in the room)
If multiple cooling In-Row Coolers are on, turn off
additional cooling In-Row Coolers by either ensuring group
control is configured properly or manually putting In-Row
Cooler(s) into standby
Dirty filter Replace filter
Refrigerant undercharged
Add charge; shall be 9-10 bar, depending on room
temperature
Expansion valve excess
superheat
Recalibrate expansion valve
Expansion valve malfunction,
replace
Filter drier plugged
Ensure temp drop across is less than 2°F
Replace if necessary
Kinked liquid line Identify and repair
Low airflow across evaporator
Replace filter
Check for obstructions
Condenser signal wiring
disconnected
Ensure condenser signal wiring is still intact
In-Row Cooler Maintenance
Time
In-Row Cooler service interval
has expired
Perform preventative maintenance, then reset timer
Indoor Fan Maintenance Time
Compressor Maintenance
Time
Outdoor Fan Maintenance
Time
Filter Maintenance Needed
2. Operation and Maintenance
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