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Troubleshooting

    Refrigerant Floodback

    This is a result of liquid refrigerant returning to the compressor during the running cycle. The oil is diluted with refrigerant to the point it cannot properly lubricate the load bearing surfaces.

    The liquid washed the oil off the pistons and cylinders during the suction stroke causing them to wear during the compression stroke.

    The liquid dilutes the oil in the crankcase and the refrigerant rich oil will be pumped to the rods and the bearings through the crankshaft. As the refrigerant boils off, there will not be enough oil for sufficient lubrication at the bearings farthest from the oil pump. The center and rear bearings may seize or may wear enough to allow the rotor to drop and drag on the stator causing it to short.

    What To Look For:

    • Air Cooled Compressors
      • Worn pistons and cylinders
      • No evidence of overheating
    • Refrigerant Cooled Compressors
      • Center and rear bearings worn or seized
      • Dragging rotor, shorted stator
      • Progressively scored crankshaft
      • Worn or broken ro

    Correction:

    • Maintain proper evaporator and compressor superheat.
    • Correct abnormally low load conditions.
    • Install accumulators to stop uncontrolled liquid return.

    Flooded Starts

    This is the result of refrigerant vapor migrating to the crankcase oil during the off cycle. When the compressor starts, the diluted oil cannot properly lubricate the crankshaft load bearing surface causing an erratic wear or seizure pattern.

    What To Look For:

    • Worn or scored rods or bearings
    • Rods broken from seizure
    • Erratic wear pattern of crankshaft

    Correction:

    • Locate compressor in warm ambient or install continuous pump down.
    • Check crankcase heater operation.

    Slugging

    This is the result of trying to compress liquid refrigerant and/or oil, in the cylinders. Slugging is an extreme floodback in air cooled compressors and a severe flooded start on refrigerant cooled compressors.

    What To Look For:

    • Broken reeds, rods, or crankshaft
    • Loose or broken backer bolts
    • Blown head gaskets

    Correction:

    • Maintain proper evaporator and compressor superheat.
    • Correct abnormally low load conditions.
    • Install accumulators to stop uncontrolled liquid return.
    • Locate compressor in warm ambient or install continuous pump down.

    High Discharge Temperature

    This is the result of temperatures in the compressor head and cylinders becoming so hot that the oil loses its ability to lubricate properly. This causes rings, pistons and cylinders to wear resulting in blow by, leaking valves, and metal debris in the oil.

    What To Look For:

    • All rods and bearings worn or scored
    • Crankshaft uniformly scored
    • Rods broken from seizure
    • Little or no oil in crankcase

    Correction:

    • Correct abnormally low load conditions.
    • Correct high discharge pressure conditions.
    • Insulate suction lines.
    • Provide proper compressor cooling.

    Loss of Oil

    This is a result of insufficient oil in the crankcase to properly lubricate the load bearing surfaces. When there is not enough refrigerant mass flow in the system to return oil to the compressor as fast atas it is pumped out, there will be a uniform wearing or scoring of all load bearing surfaces.

    What To Look For:

    • All rods and bearings worn or scored
    • Crankshaft uniformly scored
    • Rods broken from seizure
    • Little or no oil in crankcase

    Correction:

    • Check oil failure control operation if applicable.
    • Check system refrigerant charge.
    • Correct abnormally low load conditions or short cycling.
    • Check for incorrect pipe sizes and/or oil traps.
    • Check for inadequate defrosts.