Parallel Compressor Systems
Symptom |
| Cause |
| Remedy |
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Low | 1. | Insufficient refrigerant in system | 1. | Check for leaks. Repair and add charge |
Discharge | 2. | Faulty condenser temp. regulation | 2. | Check condenser control operation |
Pressure | 3. | Compressor suction or discharge valve inefficiencies | 3. | Clean or replace leaky valve plates |
| 4. | Low suction pressure | 4. | See corrective steps for low suction pressure |
| 5. | Head pressure control valve set wrong | 5. | Adjust valve or install a head pressure control valve |
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| or no head pressure control valve |
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High Suction | 1. | Excessive load | 1. | Reduce load or add additional equipment |
Pressure | 2. | Expansion valve overfeeding | 2. | Check remote bulb. Regulate superheat |
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Low Suction | 1. | Lack of refrigerant | 1. | Check for leaks. Repair and add charge |
Pressure | 2. | Evaporator dirty or iced | 2. | Defrost or clean coil |
| 3. | Clogged liquid line filter drier | 3. | Replace cartridge(s) |
| 4. | Clogged suction line or compressor | 4. | Clean strainer or replace filters |
|
| suction strainer |
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| 5. | Expansion valve malfunctioning | 5. | Check and reset for proper superheat |
| 6. | Condensing temperature too low | 6. | Check means for regulating |
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|
| condensing temperature |
| 7. | Improper TXV | 7. | Check for proper sizing |
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Little or No | 1. | Clogged suction oil strainer | 1. | Clean |
Oil Pressure | 2. | Excessive liquid in crankcase | 2. | Check crankcase heater. Reset TXV for |
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| higher superheat. Check liquid line solenoid |
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| valve for proper operation. |
| 3. | Low oil pressure safety switch defective | 3. | Replace |
| 4. | Worn oil pump | 4. | Replace |
| 5. | Oil pump reversing gear stuck in | 5. | Reverse direction of compressor rotation |
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| the wrong position |
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| 6. | Low oil level | 6. | Determine where the oil is or add oil |
| 7. | Worn bearings | 7. | Replace compressor |
| 8. | Loose fitting on oil lines | 8. | Check and tighten fittings |
| 9. | Pump house gasket leaks | 9. | Replace gasket |
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Compressor | 1. | Lack of refrigerant | 1. | Check for leaks. Repair and add charge |
Loses Oil | 2. | Excessive compression ring blowby | 2. | Replace compressor |
| 3. | Refrigerant floods back | 3. | Maintain proper superheat at compressor |
| 4. | Improper piping or traps | 4. | Correct piping |
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Compressor | 1. | Operating beyond design limits | 1. | Add facilities so that conditions are within |
Thermal |
|
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| allowable limits |
Protector | 2. | Discharge valve partially shut | 2. | Open valve |
Switch Open | 3. | Blown valve plate gasket | 3. | Replace gasket |
| 4. | Dirty condenser coil | 4. | Clean coil |
| 5. | Overcharged system | 5. | Reduce charge |
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Parallel Compressor Systems Installation & Operations Manual, October 2004 | 35 |
