Industrial Refrigeration Compressor Index Page

Compressor Failure Modes, Symptoms and Corrections

A handy reference for analysis of a failed compressor, to aid in finding the cause of failure and take corrective action.  Replacement new or remanufactured compressors fail at four times the rate of original compressors.  Thus indicating that replacement failures are caused by systems problems.

Liquid Slugging

Broken reeds rods, or crankshaft.  Loose or broken discharge bolts.  Blown gaskets.
Slugging is a result of trying to compress liquid in the cylinders.  Liquid may be either refrigerant or oil or more likely a combination of both.  Slugging is a result primarily of refrigerant migration into the oil on the off cycle.

Correction:

  1. Check pump down cycle operation
  2. Is TXV sized and operating properly.
  3. Suction line sized properly?
  4. Check unloading

Liquid Washout

Worn Pistons and/or rings.  Cylinders worn.  Scored pins.  Scored and/or broken rods.  Worn Bearings.  Scored crankshaft.
This is a result of refrigerant washing oil off surfaces.  Off cycle migration of saturated refrigerant into crankcase.  Compressor starts up resulting in a mass of foam which when pumped washes bearing surfaces of oil film necessary far proper lubrication.  WASHOUT is a minor condition of SLUGGING.

Correction:

  1. Check TXV bulb and super heat setting.
  2. Is TXV oversized?
  3. Check crankcase header, (On during off cycle.)

Liquid Dilution

Rotor Drag.  Worn bearings.  Scored and/or broken rods.  Scored Crankshaft.
This is a result of liquid refrigerant returning to compressor during running cycle.  Oil becomes diluted and lubrication for oil pump and end bearing my be adequate, but as it progresses down the crankshaft insufficient oil to lubricate the rods and main bearings will occur.

Correction:

  1. Check TXV bulb.
  2. Check superheat setting.
  3. Check defrost cycle.

High Discharge Temperature Burn

Discolored valve plate (Cannot rub off).  Overheated or burned valve reeds.  Worn rings and pistons.  Worn cylinders.  Scored rods, bearings, and crankshaft.  Spot burn in stator.
This is a result of temperatures in the compressor head and cylinders becoming too hot that the oil loses its ability to lubricate.

Correction:

  1. High compression ratio: check for low suction and high discharge pressures.  Low load and evaporator problems.
  2. Check low pressure control setting
  3. Check for dirty condenser, inoperative condenser fan and ambient temperature.
  4. Check air flow across compressor.

Lack of Lubrication

Scored bearings.  Broken rods.  Scored crankshaft.  Low oil in crankcase.
This is a results in lack of enough oil in crankcase to properly lubricate the running gear.

Correction:

  1. Check oil failure Switch.
  2. Check pipe sizing and also for oil traps
  3. Inadequate defrost.
  4. Low load.
  5. Eliminate short cycling.

Electrical

Many motors fail as a result of a mechanical or lubrication failure.  Many fail due to malfunctioning external electrical components.

General or Uniform Burn

Entire winding is uniformly overheated or burned.

Correction:

  1. Check for low voltage.
  2. Rapid cycling of compressor,
  3. Loose terminal connection.
  4. Unbalanced voltage.

Single Phase Burn

Two phases of a three phase motor are overheated or burned.
A result of not having current through the unburned phase and current only at the remaining 2 phases, thus overloading the other two phases.

Correction:

  1. Check contacts in starter and contact slide mechanism for binding.
  2. Terminal connections on compressor.
  3. Unbalanced voltage
  4. Blown fuses.

Half Winding Single Phase Burn

This shows as when one half of the motor has a single phasing condition on a PART WIND MOTOR with a two contactor system.  Half is fully burned while the other side is untouched.

Correction:

  1. Check both contactors as one will be defective.
  2. Check timer for proper time delay between primary contactor and secondary contactor.  The time delay should be a second or under.

Start Winding Burn

Only the start winding is burned in a single phase motor due to excessive current flowing through the start winding.

Correction:

  1. Check C, S, and R, wiring.
  2. Starting capacitor and/or start relay.
  3. Compressor overloaded.

Run Winding Burn

Only the run winding is burned in a single phase motor.

Correction:

  1. Check relay
  2. Check run capacitors

Primary Single Phase Burn

This will show as only one phase burned.  Other two will be O.K.  A result of losing one phase in the primary of Δ to Y or Y to Δ transformer.

Correction:

  1. Check transformer for proper voltage incoming and outgoing.

Summary

After a compressor failure, field examination of the failed compressor often will reveal symptoms of system problems.  Correction will eliminate future repeat failures.

OPERATIONAL DIFFICULTIES

Faulty expansion valve of the compressor may be caused by troubles in the refrigerant system such as faulty or incorrectly adjusted evaporator liquid expansion devices, faulty oil control or condenser troubles: all of which, are indicated by definite symptoms.  Then symptoms may be caused by incorrect conditions which must be corrected by a step by step procedure.  TABLE 2 is a chart showing various incorrect conditions, their possible causes and corrections.

TROUBLE
POSSIBLE CAUSE CORRECTIVE MEASURE

High condensing pressure.
Air or non-condensable gas in system. Purge air from condenser.
Insufficient water or air flowing through condenser. Increase quantity of water or air.
Evaporative condenser clogged or limed. Clean condenser water tubes.
Too much liquid in receiver, condenser tubes submerged in liquid refrigerant. Draw off liquid into service cylinder.

Low condensing pressure.
Too much water or air flowing through condenser. Reduce quantity of water or air.
Condensing water too cold. Reduce quantity of water.
Liquid refrigerant flooding back from evaporator. Check expansion device adjustment, examine fastening of thermal expansion valve bulb(s).
Leaky compressor discharge valve(s). Remove heads, examine valves.  Replace any found defective.

High suction pressure.
Overfeeding of expansion device. Regulate expansion valve, check bulb attachment and superheat adjustment.
Leaky suction or discharge valves. Remove head, examine valves and replace if worn.
Malfunction of compressor capacity control system. Check capacity control system.
Excess load. Reduce load to normal.

Low suction pressure.
Restricted liquid line, or suction, strainer screens. Pump down, remove restriction, examine and clean screens.
Insufficient refrigerant in system. Check for refrigerant shortage.
Too much oil in system. Remove oil.
Improper adjustment of expansion valve(s) or liquid control devise(s). Adjust device(s) for proper superheat - approximately 10°F.
Expansion valve power element dead or weak. Replace expansion valve or power element.

Compressor will not run.
Electric power cut off Check power supply.
Fuses blown. Test fuses and renew if necessary.
Overload devices tripped. Check overload devices and find cause of overload.
Low voltage. Check voltage (should be within 10% of nameplate rating).
Trouble in starting witch or control circuit. Close switch manually to test power supply.  If OK check control circuit including temperature and pressure controls and capacity control device.
Seized compressor. Repair or rebuild compressor.

Compressor runs continuously with insufficient reduction of load temperatures.
Shortage of refrigerant. Repair leak and recharge system.
Individual cylinders not loading. Check and correct pumping ability of individual cylinders - replace suction and/or discharge valves and parts as needed.

Check and correct capacity control system.
Incorrect control switch settings. Reset control switches or replace.

Compressor short cycles or stops on high pressure cutout.
Presence of air or foul gas. Purge condenser.
Insufficient water or air flowing through condenser, clogged condenser. Check -to, or air Flow.  Check for scaled or fouled tubes in water cooled condenser.  In evaporative type, check for fouled surfaces and insufficient air or spray water.

In air cooled type, checkfor fouled surfaces, or lack I air flow.

Compressor stops on Oil Failure Switch
Plugged Oil Strainer.
Excessive liquid repair in sump????

 Clean oil strainer.
Pump down observe level.  See symptoms chart.