Applicable Systems
R-Series
Symptoms
The main motor current has exceeded the rated full-load amperage (FLA) by 10% for more than 30 seconds. The controller triggers a motor overload alarm.
Possible Causes
- Low supply voltage causing the motor to draw more current to maintain torque
- Mechanical overload from a seized air end or excessive system pressure
- Motor bearing wear increasing friction and current draw
Troubleshooting Steps
- Step 1: Measure the three-phase supply voltage at the motor terminals during operation
Voltage should be within +/-5% of rated voltage; investigate low voltage - Step 2: Check the motor protection circuit breaker setting against the motor FLA on the nameplate
Adjust the thermal overload setting to match the nameplate FLA - Step 3: Perform a mechanical check by rotating the air end coupling by hand with power off
The air end should turn smoothly; if seized, schedule a rebuild
How to Reset
Reset: After the motor cools for 10 minutes and the overload relay is manually reset, press Alarm Reset on the controller.
Common Replacement Parts
- Motor bearing kit: DE and NDE bearings (Match bearing number from motor nameplate)
- Overload relay: Thermal or electronic type (Set to motor FLA)
Frequently Asked Questions
- Q: What is the normal motor temperature?
Class F insulation allows up to 155C. Surface temperature of 80-95C during operation is normal.
- Q: Can I increase the overload setting to stop nuisance trips?
No. The overload is set to protect the motor. If tripping persistently, find and fix the root cause.
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Source: Service Manual
Category: Compressor
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