18
pressure
Expansion valve overfeeding.
Check bulb location and clamping.
Adjust superheat.
Low suction
pressure.
Lack of refrigerant.
Check for leaks. Add charge.
Evaporator dirty or iced
Clean and defrost.
Clogged liquid line filter drier.
Replace filter drier.
Expansion valve malfunctioning.
Check and reset for proper superheat.
Condensing temperature too low.
Check and replace head pressure control
Improper expansion valve.
Check for proper expansion valve.
Compressor
thermal protector
switch open.
Operating beyond design conditions
Add facilities so that conditions are
within allowable limits.
Discharge valve partially closed
Open valve.
Dirty condenser coil
Clean coil
Overcharged refrigerant
Reduce charge.
Compressor loses
oil
Lack of refrigerant
Check for leaks and add refrigerant
Excessive compression ring blow by.
Replace compressor.
Refrigerant flood back.
Maintain
proper
superheat
at
compressor.
Improper piping or traps.
Correct piping.
Little or no oil
pressure
Clogged suction oil strainer.
Clean.
Excessive liquid in crankcase.
Check crankcase heater.
Adjust expansion valve.
Check the solenoid valve.
Low oil pressure safety switch defective.
Replace.
Oil pump reversing gear stuck in wrong
position.
Reverse
direction
of
compressor
rotation.
Worn bearings.
Replace compressor.
Low oil level.
Add oil.
Loose fitting on oil lines.
Check and tighten system.
Pump housing gasket leaks.
Peplace gasket.
Field Wiring.
Diagram 1. Typical wiring diagram for single evaporator with or without defrost timer.
