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Component System Analysis
Troubleshooting Chart
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| General Problem Category |
Symptoms |
Possible Causes |
| Compressors |
| Liquid Slugging
(Refrigerant or Oil)
|
-Noisy Operation |
-Inadequate Airflow Over Evaporator |
| -Excessive Vibration |
-Excessive Charge (with Fixed Metering Device) |
| -Overheating |
-Oversized TXV |
| -High Compressor Power Draw (kW) |
-Frosted Evaporator |
| -Compressor Failure |
-Crankcase Heater Inoperative |
| -Reduced Capacity |
-Pumpout Control Faulty |
| -High Saturated Suction Temperature |
-Flooded Start |
| -Compressor Does Not Pump Properly |
|
| -Zero Suction Gas Superheat |
|
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| Flooded Start |
|
-Liquid Line Solenoid Valve Stuck On |
| |
-Crankcase Heater Off or Faulty |
| -See “Liquid Slugging” Symptoms |
-Improper Piping System Design |
| |
-Pumpout Control Faulty |
| -Leaky Liquid Solenoid Valve |
| |
| Loss Of Lubricant |
-Overheating |
-Flooded Start |
| -Mechanical Seizure |
-Floodback of Liquid Refrigerant |
| -High Compressor Power Draw (kW) |
-Oil Trapped in System |
| -Failure to Start |
|
| -Noisy Operation |
| -Compressor Winding Thermostat Trips |
| -Compressor Intermittently Trips Off on Internal Motor Protection |
| |
| Contamination of Mechanical Refrigeration System |
-System Valve(s) Stick |
-Improper Evacuation/Dehydration |
| -Compressor Does Not Pump Properly |
-System Leak |
| -Compressor Failure |
-Strainer-Drier Loaded |
| -Overheating of Compressor |
-High Temperature Break Down Oil, Refrigerant And System Materials |
| -High Compressor Power Draw (kW) |
-Carbonized Valves |
| -Discoloration of moisture Indicator in Liquid Line Sight Glass |
-Sludged System |
| -Sealed-Tube Refrigerant Test Shows High Acid and/or Moisture Content |
|
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| Compressor Overheating |
-Compressor Failure |
-Condenser Dirty |
| -High Compressor Power Draw (kW) |
-Inadequate Condenser Airflow or Water Flow |
| -High Compressor Casing Temperature |
-Excessive Evaporator Superheat |
| -Compressor Safety Winding Thermostat Trips |
-Electrical Line Current and/or Voltage abnormal or unstable |
| -Failure to Pump Properly |
-Loss of Lubrication |
| |
-Undercharged or Overcharged System |
| -Liquid Slugging |
|
Condensers
|
| High Head Pressure (Saturated Condensing Temperature or Saturated Discharge Temperature) |
-Compressor Cycles off Intermittently on High Pressure Switch while System Calls for Cooling |
-Faulty Head Pressure Control Device |
| -Compressor Cycles Intermittently on Compressor Motor Protection Switch |
-Dirty Condenser Coil |
| -High Saturated Condensing Temperature |
-Faulty Condenser Fan Motor |
| -High Discharge Gas Superheat |
-Extensive Fin Damage |
| -Compressor Overheats |
-Condenser Air Re-circulation |
| -Compressor Seizure |
-Dirty Condenser Fan |
| -Compressor Motor Burnout |
-Condenser Airflow Blocked |
| -High Compressor Power Draw (kW) |
-Prevailing Winds Prohibit Proper Airflow Across Coil |
| -Low System Capacity |
-Backward Condenser Fan Rotation |
| -Saturated Suction Temperature Normal to High |
-Slipping Condenser Fan Belt |
| -Excessive Condenser Water Flow Rate |
-Bent or Broken Condenser Fan Blade(s) |
| |
-Scaled Water-Cooled Condenser Tubes |
| -Faulty Condenser Water Pump |
| -Damaged Water Pump Impeller |
| -Plugged Condenser Water Lines or Screens |
| -Condenser Water Valve Stuck Closed |
| -Cooling Tower Problems |
| -Condenser Vapor Locked by Undersized or Poorly Laid Out Refrigerant Condensate Line which Prevents Refrigerant from freely Draining to Receiver |
| -System Overcharged |
| -Noncondensible Gas Present |
| |
| Refrigerant Charge Incorrect |
-High Head Pressure |
-System Overcharged |
| -High Liquid Subcooling |
| -Low System Capacity |
| -High Saturated Suction Temperature |
| -High Compressor Power Draw |
| |
|
| -Low Head Pressure |
-System Undercharged
|
| -Low Saturated Suction Temperature |
| -Low System Capacity |
| -Low or Nonexistent Liquid Subcooling |
| -Flash Gas at Metering Device Inlet |
| |
| Low Head Pressure |
-Low Saturated Condensing Temperature |
-Faulty Head Pressure Control Device |
| -Low System Capacity |
-Refrigerant System Leak |
| -Low Saturated Suction Temperature |
-Undercharged System |
| -Low Compressor Power Draw |
-Condenser Water Valve |
|
Evaporators
|
| Low Airflow |
-Low Saturated Suction Temperature |
-Dirty Evaporator Coils (no Filters?) |
| -Low Suction Gas Superheat |
-Badly Bent Evaporator Fins |
| -Low Saturated Condensing Temperature |
-Dirty Filters |
| -Low Compressor Power Draw (kW) |
-See 'Airside-Low Airflow Over Evaporator" |
| -Low Supply Air Temperature |
|
| -Low System Capacity |
|
| -High Space Air Temperature |
|
| -Iced or Frosted Evaporator |
|
| -Compressor Slugging |
|
| -See 'Airside' for others |
|
| |
| Excessive Airflow |
-High Supply Air Temperature |
-Fan Motor Speed Set Too High |
| -High Saturated Suction Temperature |
-Wrong Fan Drive Package and/or Setting |
| -High Compressor Power Draw (kW) |
-Undersized Coil (Applied Air Handler) |
| -Noisy Air System |
Condensate Carriers Over Air Handler Drain Pan into Fan and Supply Ductwork |
| -Water Dripping from Fan and Supply Ductwork Near Air Handler |
| |
| Uneven Airflow Over Coil |
-Low System Capacity |
-Bad Duct Design near evaporator Coil |
| -Low Saturated Suction Temperature |
-Coil placement improper |
| -Uneven Condensate Coverage over Coil Surface |
-Air Turbulence at Coil |
| -Uneven Coil Surface Temperature |
-Lack of Necessary Air Baffling near Coil |
| -Refrigerant Floodback to Compressor |
-Obstruction Within Air Handler |
| -Compressor Slugging |
-Obstruction in Ductwork Near Air Handler |
| -Mismatched Coil and Air Handler |
| |
| Low Refrigerant Supply |
-Low System Capacity |
-System Undercharged |
| -Low Saturated Suction Temperature |
-Liquid Line Kinked or Crushed |
| -High Suction Gas Superheat |
-Evaporator Tube Crushed (especially return bends) |
| -Low Compressor Power Draw (kW) |
-System Refrigerant Leak |
| -Low Saturated Condensing Temperature |
-Malfunctioning Metering Device |
| -Measurable Temperature Drop in Liquid Line |
-TXV Power Element Low on Charge |
| -Visible Bubbles in Liquid Line Sight Glass |
-Undersized Metering Device |
| -High Supply Air Temperature |
-Undersized Distributor Nozzle |
| -Frosted or Iced Evaporator |
-Head Pressure Control Faulty at Low Outdoor Ambient Temperatures |
| -High Discharge Gas Superheat |
-TXV Plugged Distributor Oil Nozzle |
| -Free Water in System Forms Ice |
| |
| Uneven Refrigerant Distribution to Coil Circuits or to Cooler Circuits |
-Low system capacity |
-Plugged Evaporator feeder tube(s) |
| -Low Saturated Suction Temperature |
-Kinked or crushed feeder tube(s) |
| -Little or No Suction Gas Superheat |
-Partially blocked distributor |
| -TXV hunts |
-Oversized distributor |
| -Compressor Floodback |
-Oversized distributor nozzle (applied air handlers) |
| -Compressor Slugging |
-Improperly installed distributor (applied air handlers) |
| -Uneven Coil Surface Temperature |
-Crushed evaporator tube (especially return bends) |
| -Uneven Condensate formation on Evaporator |
-Plugged evaporator (or cooler) circuit |
| -Frost on Some areas of Evaporator but not on others |
| |
| Low Water Flow in Cooler |
-Low Saturated Suction Temperature |
-Chilled Water Pump |
| -Low Suction Gas Superheat |
-Faulty Pump Motor |
| -Low Saturated Condensing Temperature |
-Damaged or Blocked Pump Impeller |
| -Low Compressor Power Draw (kW) |
-Blocked Chilled Water Line or Valve |
| -Low Leaving Chilled Water Temperature |
-Water Baffle(s) in D-X Cooler misplaced blocking flow |
| -Low System Capacity |
-Excessive water scaling (flooded cooler) |
| -High Space Temperature |
-Reverse Chilled Water Pump Rotation |
| -High Temperature Drop Between Entering and Leaving Chilled Water |
-Blockage in Chilled Water piping |
| -Chiller shuts down Intermittently (even though thermostat calls for cooling) on low Leaving Water Safety Thermostat |
-Water flow control valve restricting Flow |
| |
| Uneven Water Flow Through Cooler |
-Low System Capacity |
-(D-X) Cooler:
-misplaced or broken baffle(s)
-excess air in water system
-debris inside shell of cooler
|
| -Low Saturated Suction Temperature |
| -Compressor Floodback |
| -Compressor Slugging |
| -High Leaving Chilled water Temperature |
-(Flooded Cooler):
-badly scaled water tube(s)
-kinked or crushed water tube(s)
-plugged water tube(s) or water box
|
| -Low Temperature drop between Entering and Leaving Chilled Water |
| |
| Low Refrigerant Supply to Cooler |
-Low System Capacity |
-System undercharged |
| -High Leaving Chilled Water Temperature |
-Head Pressure Control not working at Low Outdoor Ambient Temperatures |
| -Low Saturated Suction Temperature |
-Refrigerant System Leak |
| -High Suction Gas Superheat |
-Flooded Cooler
-refrigerant flow from condenser blocked
-cooler refrigerant supply valve stuck
|
| -Low Compressor Power Draw (kw) |
-D-X Cooler:
-liquid line or accessories plugged
-liquid line kinked or crushed
-TXV power element low on charge
-TXV plugged or stuck
-refrigerant distributor or nozzle plugged
-electronic expansion valve faulty or microprocessor problem
-frost-pinched cooler tubes
|
| -Low Saturated Condensing Temperature |
| -Space Temperature Too Warm |
| -Chiller Compressor Cycles on and off Intermittently on Low Pressure Switch |
|
Metering Devices
|
| Evaporator OverFeed ("Flooding") |
-High Saturated Capacity |
-System Overcharge (fixed metering device) |
| -Low Suction Gas Superheat |
-Oversized Metering Device |
| -Liquid Floodback |
-TXV Stuck Open |
| -Compressor Slugging |
-TXV Superheat setting too Low |
| -Compressor Overheats |
-TXV type wrong for Refrigerant in system |
| -High Compressor Power Draw (kW) |
-Uninsulated TXV sensing bulb in warm area |
| -Compressor Failure |
-Loose TXV sensing bulb |
| -Compressor Pumps improperly |
-Incorrectly located TXV sensing bulb |
| -TXV Hunts |
-Partial load too low for Metering Device |
| -Excessive Oil Circulating in System |
| -High Head Pressure (fixed metering device) |
| |
| Evaporator Underfeed ("Starvation") |
-Low System Capacity |
-System undercharged |
| -Low Saturated Suction Temperature |
-Undersized metering device |
| -High Suction Gas Superheat |
-Plugged metering device |
| -Low Compressor Power Draw (kW) |
-Plugged distributor or nozzle |
| -Low Saturated Condensing Temperature |
-Undersized distributor or nozzle (TXV jobs) |
| -High Discharge Gas Superheat |
-Kinked or crushed capillary tube |
| -High Supply Air Temperature |
-TXV stuck in closed position |
| -Iced or Frosted Evaporator |
-TXV power element low on charge |
| -Wrong TXV for refrigerant in system |
| -Plugged or crushed TXV external equalizer line |
| -TXV superheat setting too high |
| -Incorrect TXV sensing bulb location |
| -Free water in system forms ice and blocks refrigerant flow |
| -Low head pressure (fixed metering device) |
| -Faulty head pressure control device |
| |
| TXV Hunting |
-Saturated suction temperature oscilates High then Low, in a cyclical fashion |
-Oversized TXV |
| -Suction gas superheat oscilates high and low in a cyclical fashion |
-Improper part-load control operation loads TXV too lightly |
| |
-Very light cooling load |
| |
| Distributor Nozzles (TXV Applications) |
-Evaporator Underfeed (see symptoms above) |
-Undersized distributor Nozzle (quite unlikely on comfort work) |
| |
|
| -Evaporator unevenly fed by refrigerant (see symptoms on evaporator sheet) |
-Oversized Nozzle |
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-Nozzle not sized for load stability
-Faulty Part-Load control sequence for evaporator sections
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Refrigeration Accessories
|
| Plugged Filter-Drier (Liquid Line) |
-Starved evaporator symptoms (see evaporator sheet) |
-Dirty refrigeration system |
| |
-Compressor cycles on low pressure switch |
-Improper evacuation/dehydration |
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-Metal chips, scale, etc., in system from installation |
| |
| Wet Filter-Drier |
-Moisture indication sight glass shows wet |
-System Refrigerant leak |
| |
-Valves stick intermittently and system cycles off from internal blockage |
-Improper evacuation/dehydration |
| |
-Sealed Tube test of refrigerant shows wet |
-Leaking water-cooled condenser tubes |
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|
-Filter-Drier exposed to air before installation |
| |
| Undersized Filter-Drier |
-Low system capacity |
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| -Low compressor power draw (kW) |
|
| -Low saturated suction temperature |
-Bad design on field piping system |
| -Low saturated Condensing Temperature |
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| -High discharge gas superheat |
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| -Flash gas in liquid line sight glass |
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| -High liquid refrigerant subcooling |
|
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| Crankcase Heater Inoperative |
-Flooded Start:
-High Compressor power draw (kW)
-Noisy operation
-Excessive compressor vibration
-Overheating of compressor
|
-Never switched on |
| -Violent oil foaming (visible in compressor sight glass) |
-Heater element broken |
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-Control Circuit problem |
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-Electrical power or control connection loose or corroded |
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| Oil Separator Trapping Oil |
-Oil level low on compressor sight glass |
-Sludge blocking oil separator float valve orifice |
| -High compressor power draw (kW) |
-Oil separator float assemble faulty |
| -Compressor overheating |
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| -Compressor noisy |
|
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| Oil Separator Float Valve Stuck Open |
-High saturated suction temperature |
-Debris at oil separator orifice keeps float valve from seating properly |
| -High saturated condensing temperature |
-Faulty Float assembly |
| -High compressor power draw (kW) |
-Liquid refrigerant migrates through separator to compressor oil sump at shutdown |
| -Flooded Start |
|
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| 4-Way (reversing) Valve Damaged or Stuck-Heating |
-Low or no heating capacity |
-Sludge in refrigeration system |
| -Compressor cycles intermittently on internal overload |
-Acids in refrigeration system |
| -Compressor runs but low on heating capacity |
-Improper evacuation/dehydration |
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-4-way valve leaks internally |
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| Suction Line Sizing and Design |
-Low system capacity |
-Undersized suction line |
| -Low saturated suction temperature |
-Pinched suction line |
| -High compression ratio |
-Obstructed suction line |
| |
| -Compressor overheats |
-Oversized suction line |
| -Compressor noisy |
-Suction line layout creates oil entrapment |
| -High compressor power draw (kW) |
-Suction riser oversized or improperly laid out |
| -Mechanical seizure of compressor |
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| -Compressor won't start |
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| -Compressor trips off on motor protection |
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| -Contaminated system |
|
| -Compressor pumps inadequately |
|
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| -Suction line sweating |
-Lack of insulation on suction line |
| -Excessive suction gas superheat |
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| -High discharge gas superheat |
|
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| -Broken Suction line |
--Improperly laid out and/or supported near compressor |
| -Noisy line vibration |
|
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| Hot Gas Line Sizing and Design |
-Low system capacity |
-Undersized hot gas line |
| -High saturated condensing temperature |
-Pinched hot gas line |
| -High Compressor power draw (kW) |
-Obstructed hot gas line |
| -High compressor ratio |
|
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| -Compressor overheats |
-Oversized hot gas line (especially risers) |
| -Compressor noisy |
-Hot gas line layout causes oil entrapment |
| -High compressor power draw (kW) |
-Hot gas riser oversized |
| -Mechanical seizure of compressor |
-Hot gas riser laid out wrong |
| -Compressor won't start |
-Oil or liquid refrigerant backflow to compressor at shutdown or at low capacity |
| -Compressor trips off motor protection |
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| -Compressor pumps inadequately |
|
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| -Broken hot gas line |
-Ruptured (Failed) Vibrasorber |
| -Noisy line vibration |
-Improperly laid out and/or supported piping near compressor |
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Liquid Line sizing and Design
|
-Compressor noisy at startup after shutdown period |
-Lacking hot gas line check valve near condenser inlet. Liquid refrigerant lays on compressor heads |
| -Flooded start after shutdown |
-Valves damaged or broken from hydraulic forces caused by liquid on heads |
| -Compressor vibrates excessively at startup after shutdown period |
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| High compressor power draw (kW) after shutdown period |
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| -Compressor pumps inadequately |
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| -Flash gas at liquid line sight glass |
-Undersized liquid line |
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-Low saturated suction temperature
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-Pinched liquid line |
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-Low compressor power draw (kW) |
-Obstructed liquid line |
| -Low system capacity |
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| -High suction gas superheat |
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| Refrigerant Condensate Line Sizing and Design |
-Low system capacity |
-Condenser vapor lock from undersized line |
| -High saturated condensing temperature |
-Line layout prevents condenser from freely draining to receiver |
| -High discharge gas superheat |
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| -High compressor power draw (kW) |
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| Flash Gas at Metering Device Inlet |
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