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19
Table 5: PRO
3
System Troubleshooting Chart
PROBLEM POSSIBLE CAUSES POSSIBLE CORRECTIVE STEPS
Compressor will not run
1. Main switch open. 1. Close switch.
2. Fuse blown.
2
Check electrical circuits and motor winding for shorts or grounds.
Investigate for possible overloading. Replace fuse after fault is corrected.
3. Thermal overloads tripped.
3. Overloads are automatically reset. Check unit closely when unit
comes back on line.
4. Defective contactor or coil. 4. Repair or replace.
5. System shut down by safety devices.
5. Determine type and cause of shutdown and correct it
before resetting safety switch.
6. No cooling required. 6. None. Wait until calls for cooling.
7. Motor electrical trouble. 7. Check motor for open windings, short circuit or burn out.
8. Loose wiring. 8. Check all wire junctions. Tighten all terminal screws.
Compressor noisy or vibrating
1. Flooding of refrigerant into crankcase. 1. Check setting of expansion valves.
2. Worn compressor. 2. Replace.
High discharge pressure
1. Non-condensables in system. 1. Remove the non-condensables.
2. Fan not running. 2. Check electrical circuit. Replace if motor fails.
3. Dirty condenser coil. 3. Clean.
4. System overcharged with refrigerant. 4. Reclaim refrigerant and recharge proper amount.
Low discharge pressure
1. Insucient refrigerant in system. 1. Check for leaks. Repair and add charge.
2. Low suction pressure. 2. See corrective steps for low suction pressure.
High suction pressure
1. Excessive load. 1. Reduce load or add additional equipment.
2. Expansion valve overfeeding. 2. Check remote bulb. Regulate superheat.
Low suction pressure
1. Lack of refrigerant. 1. Check for leaks. Repair and add charge
2. Evaporator dirty or iced. 2. Clean.
3. Expansion valve malfunctioning. 3. Check and reset for proper superheat.
4. Condensing temperature too low. 4. Check ambient temperature 50°F to 100°F.
Compressor thermal protector
switch open
1. Operating beyond design conditions. 1. Add equipment so that conditions are within allowable limits.
2. Dirty condenser coil. 2. Clean coil.
3. Overcharged system. 3. Reduce charge
Fan(s) will not operate
1. Main switch open. 1. Close switch.
2. Blown fuses. 2. Replace fuses. Check for short circuits or overload conditions.
3. Defective motor. 3. Replace motor.
4. Defective defrost control. 4. Replace defective component.
5. Unit in defrost cycle. 5. Wait for completion of cycle.
6. Coil does not get cold enough to reset thermostat. 6. Adjust fan delay setting of control.
Room temperature too high
1. Control cut out set too high. 1. Adjust control.
2. Superheat too high. 2. Adjust thermal expansion valve.
3. System low on refrigerant. 3. Add refrigerant.
4. Coil iced-up. 4. Manually defrost coil. Check defrost controls for malfunction.
Ice accumulating on ceiling around
evaporator and/or on fan guards’
venturi or blades
1. Defrost duration is too long. 1. Adjust defrost termination temperature on control.
2. Fan delay not delaying fans after defrost period. 2. Adjust fan delay setting or replace bad sensor.
3. Defective defrost control or sensor. 3. Replace defective control or sensor.
4. Too many defrosts. 4. Adjust number of defrosts.
Coil not clearing of frost during
defrost cycle.
1. Coil temperature not getting above freezing point during defrost. 1. Check heater operation.
2. Not enough defrost cycles per day. 2. Adjust control for more defrost cycles.
3. Defrost cycle too short. 3. Adjust defrost control, defrost duration setting.
4. Defective defrost control or sensor. 4. Replace defective component.
Ice accumulating in drain pan
1. Defective heater. 1. Replace heater.
2. Unit not installed properly (out of level). 2. Check and adjust if necessary.
3. Drain line plugged. 3. Clean drain line.
4. Defective control. 4. Replace defective component.
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