Applicable Systems
Freedom Series
Symptoms
The C440 overload relay trips on thermal overload with the OL indicator active. The motor housing is hot to touch (>80C surface temperature). The feeder breaker remains closed but the contactor is open.
Possible Causes
- Motor ventilation blocked by debris or external enclosure
- Excessive duty cycle with too many starts per hour
- High ambient temperature in the MCC room (>40C)
- Incorrect overload heater or electronic setting for the motor FLA
Troubleshooting Steps
- Step 1: Clear the motor cooling fan cover and ventilation passages of dust or debris
Air flows freely through the motor cooling fins - Step 2: Review the number of starts in the past hour against the motor nameplate maximum
Start count is within the allowed starts per hour (typically 3-6) - Step 3: Measure the ambient temperature in the MCC room and verify HVAC operation
Room temperature is <40C or within the design specification - Step 4: Verify the C440 current setting matches the motor nameplate FLA exactly
Setting is within 105% of motor FLA and the trip class matches application duty
How to Reset
Allow the motor to cool for at least 15 minutes. Press the C440 reset button. Re-energize the contactor after confirming the motor temperature is below the relay reset threshold.
Common Replacement Parts
- C440A1A120SXN: Eaton C440 electronic overload relay (Verify trip class (10/20/30) matches motor thermal capacity)
Frequently Asked Questions
- Q: Why does the motor overheat only in summer?
Increased ambient temperature and reduced HVAC capacity are the most common seasonal causes. Check room airflow and filter condition.
- Q: What trip class should I use for a standard pump motor?
Class 10 is typical for general-purpose motors. Class 20 or 30 may be needed for high-inertia loads such as centrifuges or large fans.
Comments (0)
Share your experience to help others facing the same problem.
Leave a Comment
Source: Eaton Freedom Series Motor Control Centers Technical Data, TD01901007E
Category: Electrical
No comments yet. Be the first to share your experience!