1. R4 Troubleshooting Refrigeration
R4 Troubleshooting Refrigeration - Subject 1 Compressor Problems v1.1
11/28/2018
R4 Troubleshooting Refrigeration
#1 Compressors Problems
© 2004 Refrigeration Training Services
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2. Common Causes of Compressor Failures
R4 Troubleshooting Refrigeration - Subject 1 Compressor Problems v1.1
11/28/2018
Common Causes of Compressor Failures
Liquid slugging
Floodback
Flooded start
Overheating
© 2004 Refrigeration Training Services - R4 Subject 1 Compressor Problems v1.2
© 2004 Refrigeration Training Services
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3. Liquid Slugging “Slug” of liquid on piston head
Breaks valves, pistons, rods, and crankshafts
Compressors cannot compress liquid
© 2004 Refrigeration Training Services - R4 Subject 1 Compressor Problems v1.2

4. Slugging: broken suction valves
R4 Troubleshooting Refrigeration - Subject 1 Compressor Problems v1.1
Slugging: broken suction valves
11/28/2018
LIQUID
If a large slug of liquid is drawn through the suction port, the mass and inertia of the liquid will drive the tip of the reed against the reed stop. The strain can eventually bend or break the tip.
© 2004 Refrigeration Training Services - R4 Subject 1 Compressor Problems v1.2
© 2004 Refrigeration Training Services
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5. Slugging: broken discharge reed valves
R4 Troubleshooting Refrigeration - Subject 1 Compressor Problems v1.1
11/28/2018
During the compression stroke, the slug of refrigerant liquid oil is driven through the discharge port. That may be with such force that the reed may be broken, the backer bent, or hold down bolts broken or stripped.
Discharge reed valve snapped off here
© 2004 Refrigeration Training Services - R4 Subject 1 Compressor Problems v1.2
© 2004 Refrigeration Training Services
No reproduction or unauthorized use allowed

6. Slugging: gaskets & broken crankshafts
R4 Troubleshooting Refrigeration - Subject 1 Compressor Problems v1.1
11/28/2018
Crankshaft Sheared off
Due to the tremendous hydraulic force generated by slugging, gaskets can blow. Also, connecting rods and crankshafts can be bent or broken.
Blown Gasket
© 2004 Refrigeration Training Services - R4 Subject 1 Compressor Problems v1.2
© 2004 Refrigeration Training Services
No reproduction or unauthorized use allowed

7. Floodback Liquid droplets in suction vapor Air cooled compressors:
Washes lubricant from cylinder walls
Suction cooled compressors:
Washes lubricant from crankshaft
© 2004 Refrigeration Training Services - R4 Subject 1 Compressor Problems v1.2

8. Picture of piston worn by lack of lubrication
R4 Troubleshooting Refrigeration - Subject 1 Compressor Problems v1.1
11/28/2018
Floodback:
Air Cooled Compressor
Picture of piston worn by lack of lubrication
This is one of the pistons from that compressor. Even though it ran for only a few hours and no slugging noise was heard, the results are obvious. The washing action of the liquid refrigerant removed the oil from the surfaces allowing metal to rub directly on metal.
Washed away cylinder lubrication
© 2004 Refrigeration Training Services - R4 Subject 1 Compressor Problems v1.2
© 2004 Refrigeration Training Services
No reproduction or unauthorized use allowed

9. Picture of crankshaft damaged by flooding
Floodback: Suction Cooled Compressors
R4 Troubleshooting Refrigeration - Subject 1 Compressor Problems v1.1
11/28/2018
Picture of crankshaft damaged by flooding
Oil Pump End
Lots of Damage
Motor End
Some damage
The diluted oil contains enough refrigerant to reduce the volume of oil available for bearing lubrication. As the refrigerant boils off in the drive train, the shortage of oil results in a progressive wear pattern that gets worse as you move farther from the oil pump. The most severe damage will be present at the bearings closest to the motor.
No damage
© 2004 Refrigeration Training Services - R4 Subject 1 Compressor Problems v1.2
© 2004 Refrigeration Training Services
No reproduction or unauthorized use allowed

10. Picture: motor burn from bearing damage by flooding
R4 Troubleshooting Refrigeration - Subject 1 Compressor Problems v1.1
Flooding: Suction Cooled Compressor
11/28/2018
Picture: motor burn from bearing damage by flooding
Burnout from electrical problem?
No. Flooding damaged bearing
Rotor dropped
As the motor end bearings wear significantly, the crankshaft will drop, causing the rotor to drag on the stator. That will result in a shorted or burned motor. If the compressor is not examined after it fails, the cause of the motor failure will remain unknown.
Hit stator, causing burnout.
© 2004 Refrigeration Training Services - R4 Subject 1 Compressor Problems v1.2
© 2004 Refrigeration Training Services
No reproduction or unauthorized use allowed

11. Slugging and Flooding - Causes and Cures
1. Low evaporator load
Causes
Space temperature too low
Air flow / dirty coil problems
Cures
Operate at design temperatures
Proper airflow and clean evaporators
2. Metering device problems
Cause
Flooding evaporator
Cure
Maintain proper superheat
© 2004 Refrigeration Training Services - R4 Subject 1 Compressor Problems v1.2

12. Diagnosing suction line frost
What does it mean?
Floodback?
Slugging?
Low on charge?
Frost means:
The suction line is below 32°
You must determine IF there is a problem
© 2004 Refrigeration Training Services - R4 Subject 1 Compressor Problems v1.2

13. Picture: Floodback on Med. Temp compressor
R4 Troubleshooting Refrigeration - Subject 1 Compressor Problems v1.1
11/28/2018
Picture: Floodback on Med. Temp compressor
Not good
Floodback on Medium Temperature Compressor
Many times liquid refrigerant can return to a compressor in small enough quantities that the heat of compression will vaporize the liquid and no noise will be heard. This picture shows an air cooled compressor in our lab with a metered amount of liquid refrigerant being fed into the suction line. The quantity fed was increased until noise was heard. The compressor was then disassembled for inspection. Did any damage result? Yes. Keep in mind, frost on a suction line and compressor does not mean liquid.
© 2004 Refrigeration Training Services - R4 Subject 1 Compressor Problems v1.2
© 2004 Refrigeration Training Services
No reproduction or unauthorized use allowed

14. Picture: frost on freezer compressor
R4 Troubleshooting Refrigeration - Subject 1 Compressor Problems v1.1
11/28/2018
Picture: frost on freezer compressor
Freezer compressor: problem or not?
Suction line: 0°F
Suction pressure: 16 psig R404A
-20°F
Superheat: 0 - (-20°) =
+20°
This compressor may appear to have liquid refrigerant returning. However, the return line, when proper analysis is completed, is actually operating with 10°F superheat. The actual line temperature is -30°F. The saturated refrigerant temperature equivalent is -40°F; therefore, no liquid can be present.
Is there a problem? NO
© 2004 Refrigeration Training Services - R4 Subject 1 Compressor Problems v1.2
© 2004 Refrigeration Training Services
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15. Flooded Start During “off-cycle”: During start-up:
Refrigerant vapor migrates to coldest spot
Vapor condenses to liquid in crankcase
Liquid refrigerant sinks under compressor oil
During start-up:
Liquid under the oil “explodes” within crankcase
Dilutes oil on crankshaft bearing surfaces
© 2004 Refrigeration Training Services - R4 Subject 1 Compressor Problems v1.2

16. Refrigerant Migration
R22 (vapor) migrates to compressor oil
R4 Troubleshooting Refrigeration - Subject 1 Compressor Problems v1.1
Compressor Start-up
Compressor is OFF
11/28/2018
Refrigerant Migration
This slide shows the refrigerant migrating to the oil and laying under the oil in the crankcase of the compressor.
The more refrigerant under the oil the higher the level of the oil. If the rod caps or crankshaft hits the oil it could damage the compressor.
OIL
R22
© 2004 Refrigeration Training Services - R4 Subject 1 Compressor Problems v1.2
© 2004 Refrigeration Training Services
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17. Refrigerant Migration
R22 (vapor) migrates to compressor oil
R4 Troubleshooting Refrigeration - Subject 1 Compressor Problems v1.1
Compressor Start-up
11/28/2018
Foaming refrigerant and oil is
pulled out of the crankcase
Refrigerant Migration
This slide shows the refrigerant migrating to the oil and laying under the oil in the crankcase of the compressor.
The more refrigerant under the oil the higher the level of the oil. If the rod caps or crankshaft hits the oil it could damage the compressor.
OIL
R22
© 2004 Refrigeration Training Services - R4 Subject 1 Compressor Problems v1.2
© 2004 Refrigeration Training Services
No reproduction or unauthorized use allowed

18. Picture: crankshaft damaged by flooded start
R4 Troubleshooting Refrigeration - Subject 1 Compressor Problems v1.1
Evidence of Flooded Start
11/28/2018
Picture: crankshaft damaged by flooded start
Scored surface
The random pattern will result in damage to the bearing surface with no damage to the bearings on either side. The damage cannot be explained by oil flow. A good, bad, good, bad sequence will be present.
Normal wear
Normal wear
Random pattern of damage
© 2004 Refrigeration Training Services - R4 Subject 1 Compressor Problems v1.2
© 2004 Refrigeration Training Services
No reproduction or unauthorized use allowed

19. R4 Troubleshooting Refrigeration - Subject 1 Compressor Problems v1.1
Crankcase heater
11/28/2018
How do we prevent flooded starts?
Install crankcase heater
(See accessories section)
Or, pump-down solenoid (See valve section)
© 2004 Refrigeration Training Services - R4 Subject 1 Compressor Problems v1.2
© 2004 Refrigeration Training Services
No reproduction or unauthorized use allowed

20. Compressor Overheating
High heat causes lubrication breakdown
Parts seize
Carbon deposits form:
On valve plates
Clog filter-driers
© 2004 Refrigeration Training Services - R4 Subject 1 Compressor Problems v1.2

21. Picture: carbon deposits on valves & plates
R4 Troubleshooting Refrigeration - Subject 1 Compressor Problems v1.1
Overheating: Carbon deposits on valves and plates
11/28/2018
Picture: carbon deposits on valves & plates
The most obvious effect of overheating is the breakdown of oil and carbonization at the discharge reed and discharge side of the valve plate. The valve plate shown here has a carbon build up due to oil breakdown. Note the copper plating of the valve seating surfaces. Copper plating is a byproduct of heat as are moisture and carbon.
© 2004 Refrigeration Training Services - R4 Subject 1 Compressor Problems v1.2
© 2004 Refrigeration Training Services
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22. Picture: drier clogged with carbon deposits
R4 Troubleshooting Refrigeration - Subject 1 Compressor Problems v1.1
Overheating: Carbon deposits in filter-driers
11/28/2018
Picture: drier clogged with carbon deposits
The creation of carbon deposits can also plug dryers as shown here.
© 2004 Refrigeration Training Services - R4 Subject 1 Compressor Problems v1.2
© 2004 Refrigeration Training Services
No reproduction or unauthorized use allowed

23. Picture: piston rings damaged by heat
R4 Troubleshooting Refrigeration - Subject 1 Compressor Problems v1.1
Overheating: Oil breaks down, parts seize
11/28/2018
Picture: piston rings damaged by heat
The hottest point of the compressor is the discharge valve port. Just below that is the the top of the piston and the cylinder walls. The heat generated here heats the walls faster than the suction vapor can cool the area. The heat thins the oil allowing metal to metal contact. The result is worn pistons, cylinder walls, and rings if the compressor has rings like the ones shown here. The wear has two main results affecting compressor operation.
© 2004 Refrigeration Training Services - R4 Subject 1 Compressor Problems v1.2
© 2004 Refrigeration Training Services
No reproduction or unauthorized use allowed

24. Compressor Overheating - Causes and Cures
1. High condensing temperatures
Causes
Low air flow / dirty condenser
Overcharge / non-condensables
Cures
Check fans / clean condenser
Verify proper condenser split / subcooling
2. High discharge temperatures
Cause
Lack of cool refrigerant / high superheat
Cure
Maintain proper superheat
Keep suction pressures up
© 2004 Refrigeration Training Services - R4 Subject 1 Compressor Problems v1.2

25. Inside View of Valve and Gasket Problems
The following 4 slides describe:
Bad discharge valve
From overheating or liquid slugging
Worn piston or rings
From overheating or floodback
Broken suction valve
From liquid slugging
Blown head gasket
© 2004 Refrigeration Training Services - R4 Subject 1 Compressor Problems v1.2

26. R4 Troubleshooting Refrigeration - Subject 1 Compressor Problems v1.1
Bad Discharge Valve
11/28/2018
Downstroke can’t open suction valve
Refrigerant not moving
Low side pressures start to rise
Compressor can’t pump
High pressure drops
Causes:
1. Overheating
2. Slugging
As the piston nears the bottom of its stroke, the pressure difference in the cylinder will not be low enough to keep the suction reed down and it will close the suction port. Thus we should recognize that the suction port is open for only a portion of the suction stroke of the piston.
© 2004 Refrigeration Training Services - R4 Subject 1 Compressor Problems v1.2
© 2004 Refrigeration Training Services
No reproduction or unauthorized use allowed

27. R4 Troubleshooting Refrigeration - Subject 1 Compressor Problems v1.1
Worn Piston or Rings
11/28/2018
Discharge gas “blows by” piston
Discharge gas enters low side
Compressor can’t pump
Low side pressures rise
High pressure drops
Causes:
1. Overheating
2. Floodback
As the piston nears the bottom of its stroke, the pressure difference in the cylinder will not be low enough to keep the suction reed down and it will close the suction port. Thus we should recognize that the suction port is open for only a portion of the suction stroke of the piston.
© 2004 Refrigeration Training Services - R4 Subject 1 Compressor Problems v1.2
© 2004 Refrigeration Training Services
No reproduction or unauthorized use allowed

28. R4 Troubleshooting Refrigeration - Subject 1 Compressor Problems v1.1
Discharge gas enters suction
Broken Suction Valve
11/28/2018
Compressor can’t pump
Low side pressures rise
High pressure drops
Cause:
Liquid Slugging
As the piston nears the bottom of its stroke, the pressure difference in the cylinder will not be low enough to keep the suction reed down and it will close the suction port. Thus we should recognize that the suction port is open for only a portion of the suction stroke of the piston.
© 2004 Refrigeration Training Services - R4 Subject 1 Compressor Problems v1.2
© 2004 Refrigeration Training Services
No reproduction or unauthorized use allowed

29. R4 Troubleshooting Refrigeration - Subject 1 Compressor Problems v1.1
Discharge gas enters suction
Blown Gasket
11/28/2018
Low side pressures rise
High pressure drops
Cause:
Liquid Slugging
As the piston nears the bottom of its stroke, the pressure difference in the cylinder will not be low enough to keep the suction reed down and it will close the suction port. Thus we should recognize that the suction port is open for only a portion of the suction stroke of the piston.
© 2004 Refrigeration Training Services - R4 Subject 1 Compressor Problems v1.2
© 2004 Refrigeration Training Services
No reproduction or unauthorized use allowed

30. End of Compressor Troubleshooting
© 2004 Refrigeration Training Services - R4 Subject 1 Compressor Problems v1.2