troubleshooting refr systems

8/13/2019 Troubleshooting Refr Systems

1/12

Sept. 2007 D.RAVINDRA

TROUBLESHOOTING COMPRESSORS

PROBLEM AREAS WHICH CAUSE COMPRESSOR

FAILURES :

FLOODING OF LIQUID REFRIGERANT INTO CCASE

FLOODED START

SLUGGING OF LIQUID REFRIGERANT / OIL INTO THECOMPRESSION AREAS OF THE COMPR.

LOSS OF LUBRICATION

CONTAMINATION OF REFR. SYSTEM WITH AIR, MOISTUREOR DIRT.

OVERHEATING OF THE COMPR. MOTOR, CYLINDER HEADVALVES, BEARINGS.

ELECTRICAL IRREGULARITIES IN VOLTAGE & CURRENT.

INCORRECT INSTALLATION.


2/12


COMPRESSOR PROBLEMS

SYMPTOMS

NOISE

FAILURE TO PUMP PROPERLY OVERHEATING

MECHANICAL SEIZURE

FAILURE TO START


3/12


REFRIGERANT FLOODBACK

LIQUID REFRIGERANT FINDS ITS WAY TO THE COMPRESSORDURING RUNNING CYCLE.

INTERNAL SYMPTOMS

WORN PISTONS, RINGS, CYLINDER WALLS, WRIST PINS /

HOLES, SCORED / BROKEN RODS, BEARINGS. DRAGGING ROTOR, SPOTBURNED MOTOR.

CORRECTION

ADJUST TEV TO INCREASE SUPERHEAT.

REDUCE CHARGE IN AN OVERCHARGED CAPILLARYSYSTEM.

CHECK IF COOLING LOAD IS TOO LOW.

USE SUCTION LINE ACCUMULATOR.


4/12


REFRIGERANT MIGRATION

REFRIGERANT MIGRATES INTO COMPRESSOR

DURING OFF-CYCLE.

INTERNAL SYMPTOMS

BOTTOM BEARING WORN / SCORED.

DAMAGED INTERNAL COMPONENTS. FLOODED START.

CORRECTION

LIMIT REFRIGERANT CHARGE.

LOCATE COMPRESSOR IN WARM AMBIENT. USE CRANKCASE HEATER.

ADOPT PUMP DOWN CYCLE.


5/12


SLUGGING

COMPRESSOR ATTEMPTING TO COMPRESS LIQUIDREFRIGERANT / OIL.

INTERNAL SYMPTOMS

BROKEN RODS AND / OR CRANKSHAFT, VALVE REEDS.

BLOWN CYLINDER HEAD & VALVE PLATE GASKET. LOOSE CYLINDER BOLTS.

CORRECTION

SAME AS FOR FLOODBACK AND MIGRATION. .


6/12


OVERHEATING

INTERNAL SYMPTOMS VARNISHED, DISCOLOURD VALVE PLATE.

CAKED CARBON IN DISCHARGE AREA.

WORN RINGS, PISTONS, CYLINDERSM, REAR BEARINGS.

OVERHEATED VALVE REEDS. DISCOLOURED LUBRICANT.

CAUSES RAISE SUCTION PRESSURE, LOWER DISCHARGE

PRESSURE. REDUCE SUPERHEAT OF INCOMING SUCTION GAS.

INSULATE SUCTION LINE TO REDUCE HEAT PICK-UP.

OIL COOLER / LIQUID INJECTION.


7/12Sept. 2007 D.RAVINDRA

AIR-COOLED CONDENSERS

PROBLEM

HIGH HEAD PRESSURE : COMPR. TRIPS ON HP SWITCH.

LOW HEAD PRESSURE

CAUSES / CORRECTION DIRTY , CLOGGED COIL : CLEAN COIL.

RESTRICTED AIR INLET / OUTLET.

SHORT CYCLING OF HOT DISCHARGE AIR.

FAN SPEED LOW / REVERSE ROTATION.

NON-CONDENSIBLES IN SYSTEM.

OVERCHARGING OF REFRIGERANT.

LOW AMBIENT TEMPERATURES : HEAD PRESSURE

CONTROL.


8/12Sept. 2007 D.RAVINDRA

AIR-COOLED EVAPORATORS

PROBLEM

INADEQUATE COOLING CAPACITY.

FROSTING OR ICING OF COIL.

LOW SUCTION PRESSURE.

LOW TEMP. OF AIR OFF THE COIL.

CAUSES / CORRECTION

DIRTY , CLOGGED COIL : CLEAN COIL.

DIRTY AIR FILTERS.

RESTRICTED AIR INLET / OUTLET.

FAN SPEED LOW / REVERSE ROTATION. LOW REFRIGERANT CHARGE. .

UNVEVEN DISTRIBUTION TO COIL CIRCUITS.


9/12


UNEVEN REFRIGERANT DISTRIBUTION TO

EVAPORATOR CIRCUITS

SYMPTOMS

SHORTAGE OF COOLING CAPACITY

NO CONDENSATION ON SOME EVAP. CIRCUITS

SOME CIRCUITS DRY, SOME SWEATING & SOME

FROSTED ON SAME EVAPORATOR COIL.

CAUSES

PLUGGED OR RESTRICTED DISTRIBUTOR TUBES

DISTRIBUTOR NOZZLE (ORIFICE) IMPROPERLY SIZED.

UNEVEN AIRFLOW OVER EVAPORATOR COIL.


10/12


HUNTING OF EXPANSION VALVE

HUNTING IS A PHENOMENON OF UNSTABLE EXPANSIONVALVE OPERATION.

SYMPTOMS

UNSTABLE EVAPORATING PRESSURE

UNSTABLE SUCTION SUPERHEAT.

CAUSES

OVERSIZED EXPANSION VALVE

STICKING OR BINDING EXPANSION VALVE PARTS

LIGHT COOLING LOAD RAPID CHANGES IN COOLING LOAD

RAPID CHANGES IN CONDENSING TEMP. / PRESSURE.

INTERMITTENT FLASHING OF REFRIGERANT IN LIQUID LINE.

LONG EVAPORATOR REFRIGERATION CIRCUITS.


11/12


EXPANSION VALVE OVERFEEDS

REFRIGERANT TO EVAPORATOR

SYMPTOMS INADEQUATE SUPERHEAT OR NO SUPERHEAT LIQUID FLOODBACK TO COMPRESSOR

LIQUID SLUGGING

EXCESSIVE OIL FOAMING IN COMPRESSOR CRANKCASE

CAUSES EXPANSION VALVE STUCK IN OPEN POSITION

OVERSIZED EXPANSION VALVE

SUPERHEAT SETTING ON VALVE TOO LOW

IMPROPER LOCATION OF SENSING BULB SENSING BULB LOOSE (NOT CLAMPED ON EVP OUTLET)

WRONG TYPE OF VALVE FOR THE REFRIGERANT USED

LIGHT COOLING LOAD

EXCESS OIL IN THE SYSTEM


12/12


EXPANSION VALVE UNDERFEEDS

REFRIGERANT TO EVAPORATOR

SYMPTOMS HIGH SUPERHEAT

SHORTAGE OF COOLING CAPACITY

LOW COMPRESSOR DISCHARGE PRESSURE / TEMPERATURE

CAUSES EXPANSION VALVE STUCK IN CLOSED POSITION

LOSS OF GAS CHARGE IN POWER ELEMENT OF EXPN. VALVE

SUPERHEAT SETTING ON VALVE TOO HIGH

IMPROPER LOCATION OF SENSING BULB OF EXPN. VALVE

PLUGGED PRESSURE EQUALIZER LINE

WRONG TYPE OF VALVE FOR THE REFRIGERANT USED

INADEQUATE REFRIGERANT CHARGE IN SYSTEM

PLUGGED REFRIGERANT FILTER-DRIER / DISTRIBUTOR

troubleshooting refr systems

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