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Table 7. System Troubleshooting Chart
PROBLEM
Compressor will not run
Compressor noisy or vibrating
High discharge pressure
Low discharge pressure
High suction pressure
Low suction pressure
Little or no oil pressure
Compressor loses oil
Compressor thermal protector
switch open.
14
POSSIBLE CAUSES
1.
Main switch open.
2.
Fuse blown.
3.
Thermal overloads tripped.
4.
Defective contactor or coil.
5.
System shut down by safety devices.
6.
No cooling required.
7.
Liquid line solenoid will not open.
8.
Motor electrical trouble.
9.
Loose wiring.
10. Phase loss monitor inoperative.
1.
Flooding of refrigerant into crankcase.
2.
Improper piping support on suction or
liquid line.
3.
Worn compressor.
4.
Scroll compressor rotation reversed.
1.
Non-condensables in system.
2.
System overcharges with refrigerant.
3.
Discharge shutoff valve partially closed.
4.
Fan not running.
5.
Head pressure control setting.
6.
Dirty condenser coil.
1.
Faulty condenser temperature regulation.
2.
Suction shutoff valve partially closed.
3.
Insufficient refrigerant in system.
4.
Low suction pressure.
5.
Variable head pressure valve.
1.
Excessive load.
2.
Expansion valve overfeeding.
1.
Lack of refrigerant.
2.
Evaporator dirty or iced.
3.
Clogged liquid line filter drier.
4.
Clogged suction line or compressor
suction gas strainers.
5.
Expansion valve malfunctioning.
6.
Condensing temperature too low.
7.
Improper TXV.
1.
Clogged suction oil strainer.
2.
Excessive liquid in crankcase.
3.
Low oil pressure safety switch defective.
4.
Worn oil pump.
5.
Oil pump reversing gear stuck in wrong
position.
6.
Worn bearings.
7.
Low oil level.
8.
Loose fitting on oil lines.
9.
Pump housing gasket leaks.
1.
Lack of refrigerant.
2.
Excessive compression ring blowby.
3.
Refrigerant flood back.
4.
Improper piping or traps.
1.
Operating beyond design conditions.
2.
Discharge valve partially shut.
3.
Blown valve plate gasket.
4.
Dirty condenser coil.
5.
Overcharged system.
POSSIBLE CORRECTIVE STEPS
1.
Close switch.
2.
Check electrical circuits and motor winding
for shorts or grounds. Investigate for possible
overloading. Replace fuse after fault is corrected.
3.
Overloads are automatically reset. Check
unit closely when unit comes back on line.
4.
Repair or replace.
5.
Determine type and cause of shutdown and
correct it before resetting safety switch.
6.
None. Wait until calls for cooling.
7.
Repair or replace coil.
8.
Check motor for open windings, short circuit
or burn out.
9.
Check all wire junctions. Tighten all
terminal screws.
10. Refer to page 18.
1.
Check setting of expansion valves.
2.
Relocate, add or remove hangers.
3.
Replace.
4.
Rewire for phase change.
1.
Remove the non-condensables.
2.
Remove excess.
3.
Open valve.
4.
Check electrical circuit.
5.
Adjust.
6.
Clean.
1.
Check condenser control operation.
2.
Open valve.
3.
Check for leaks. Repair and add charge.
4.
See corrective steps for low suction
pressure.
5.
Check valve setting.
1.
Reduce load or add additional equipment.
2.
Check remote bulb. Regulate superheat.
1.
Check for leaks. Repair and add charge.
2.
Clean.
3.
Replace cartridge (s).
4.
Clean strainers.
5.
Check and reset for proper superheat.
6.
Check means for regulating condensing
temperature.
7.
Check for proper sizing.
1.
Clean.
2.
Check crankcase heater. Reset expansion
valve for higher superheat. Check liquid line
solenoid valve operation.
3.
Replace.
4.
Replace.
5.
Reverse direction of compressor rotation.
6.
Replace compressor.
7.
Add oil and/or through defrost.
8.
Check and tighten system.
9.
Replace gasket.
1.
Check for leaks and repair. Add refrigerant.
2.
Replace compressor.
3.
Maintain proper superheat at compressor.
4.
Correct piping.
1.
Add facilities so that conditions are within
allowable limits.
2.
Open valve.
3.
Replace gasket.
4.
Clean coil.
5.
Reduce charge.
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