Troubleshooting - Vertiv Liebert PFD Installer/User Manual

9 TROUBLESHOOTING

Table 9.1 below, lists problems you may encounter, the possible cause, and a suggested remedy.
Table 9.1 Troubleshooting
Problem
Unit will not start
High discharge
pressure
Low discharge
pressure
Low suction
pressur/compressor
cycling
9 Troubleshooting
Cause Remedy
No power to unit Check voltage at input terminal block.
Check for 24 VAC ±2 VAC at control connections 1 & 2.
If there is voltage, then:
Compressor contactor
not pulling in
If there is no voltage between 1 & 2, then:
Control voltage fuses (at
transformer in evaporator Locate short and replace fuses.
module) open
Short cycle prevention
Control software delays compressor 3 minutes from stop to start.
control
Compressor high Check for 24VAC ±2VAC at control connections 2 & 3. Remove 24VAC signal at
discharge pressure/ Connection 2 by turning indoor unit control off, then back on, or by raising the
lockout relay setpoint to remove the cab for cooling, then resetting to re-establish operation.
Insufficient air flow across
Check fan operation. Remove debris from coil and air inlets.
condenser coil
High refrigerant charge Check refrigerant charge.
Faulty head pressure
Replace if defective.
control valve
Compressor rotation in
Check for proper power phase wiring to unit and to compressor motor.
reverse direction
Insufficient refrigerant in
Check for leaks; repair and add refrigerant.
system
Plugged filter drier Replace filter drier.
Improper superheat
Reset expansion valve for 10-15°F (5.6 to 8.4°C) superheat at evaporator.
adjustment
Defective liquid line
Check valve and coil; replace if necessary.
solenoid valve
• Check 24 VAC at control connections 3 and 6. If there is voltage,
then there is compressor high discharge pressure situation. The
compressor will attempt to start once the high-pressure situation
has resolved.
• Check 24 VAC at control connections 5 and 6. If there is no voltage,
then there is high discharge temperature situation. The
compressor will attempt to start once the high-temperature
situation has resolved and minimum 30 min have elapsed.
• Check control settings for cooling requirement.
• Check 24 VAC at control connections 3 and 6. If there is voltage,
there is compressor lock-out due to high discharge pressure
condition. Check display for high pressure alarm. Set S302 to 0 or
recycle power to indoor unit.
• Check 24 VAC at control connections 5 and 6. If there is no voltage,
there is compressor lock-out due to high discharge temperature
condition. Check display for high temperature alarm. Set S303 to 0
or recycle power to indoor unit.
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