[Admin]

1. Loss of Oil from Crankcase

– Operational leakage

– Foaming

– Suction pressure drops rapidly from evaporator

– Compressor running on high capacity (unloading setting)

Action

– Use defoaming agent during prolong shut down

– Shut stop valve in liquid supply line to expansion valve

– Suction and discharge valves to shut after shut-down

– Ensure unloading device in good working condition

– Install a suitable type or size expansion valve

 

2. Excessive Loss of Oil Loss in Crankcase

– Overloading of oil separator

– Drop in crankcase pressure (foaming)

– Oil passing to the condenser and to the rest of the system

 

3. Indication of Refrigerant Leakages

– Low refrigerant level in sight glass

– Large bubbles in sight glass

– Oil weeping at joint and connection

– Low suction pressure ( Relative lower pressure indicated across system)

– High superheat at compressor suction

– Compressor running continuously not maintaining room temperature

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4. Fall Off in Refrigerant Effect (Over a short period of time)

– Refrigeration loss thru shaft gland, pipes, fittings etc

– Broken suction or discharge valves

– Belt slipping

– Icing of expansion valve

 

5. High Pressure Cut-out

– Insufficient or intermittent water flow for condenser cooling

– Scaled or fouled condenser

– Overcharging of refrigerant

 

6. Low Pressure Cut-out, Short-cycling

– Evaporator coils heavily frosted

– Strainer chocked

– Leaky discharge valves

– Defective expansion valve

– Refrigerant undercharge

– Too cold inlet cooling water temperature

 

7. Refrigerant Undercharged

– Large bubbles noted in sight glass

– Low suction & delivery pressure

– Continuous running of compressor-room temp not reducing

– Relative less frosting on compressor suction line/valve

– System performance drops –of course

 

shortage of refrigerant at the evaporator :

– Filter/Drier partially block

– Leakages

– Chocked filter for thermostatic expansion valve

– Incorrect type or wrong setting of expansion valve used

 

8. Refrigerant Overcharged

– Sight glass refrigerant level higher than normal

– Higher HP/delivery pressure

– Compressor stopping on HP cutout

– Severe frosting on compressor suction line/valve

 

9. Moisture in the System

– Frosting on inlet side of expansion valve

– Low suction pressure

– HOW moisture gets into the system ??

Actions

Renew drier

 

10. Frost on Evaporator Coils

– Compressor runs longer

– Short cycling on LP switch

– Performance drops

– Low suction pressure –Refrigerant temperature drops to 0 degree Celsius or lower

 

11. Compressor Drawing-in Refrigerant Liquid

– Excessive frosting at suction valve

– Oil level at compressor sump reduced

– High suction pressure

– Noisy compressor operation

 

12. Noisy Compressor

– Liquid knock / hammering

– Lack of lubrication

– Internal components damaged

 

13. Air in the System

– High condenser pressure (HP pressure)

– Jumping of pressure gauges pointer

– Compressor noisy

– Small bubbles at sight glass

– Relative small difference in SW in & out temperature –Less heat transfer

 

14. Poor Cooling in Condenser

– Restricted cooling water

– High condenser pressure

– Incorrect temperature reading

– Water pump fault

– Choked strainer

– Dirty blocked tubes

– High SW temperature

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