Why Is Your Overload Relay Tripping? 5 Common Causes & Troubleshooting Tips

An overload relay typically trips to protect a motor from excessive current that causes overheating. Troubleshooting involves checking the motor load, relay settings, power supply, environment, and the relay itself. These steps help you identify why the relay trips and how to stop it from happening again.

Let’s walk through the five most common causes of overload relay tripping and the fixes that actually work.

Cause 1: Mechanical Overload

A motor that works beyond its rated capacity will eventually trigger an overload relay trip. This often happens when pumps clog, conveyor belts jam, or bearings wear out. The motor draws higher current to compensate, and the relay shuts it down.

Troubleshooting:

• Inspect the motor-driven equipment for blockages, jams, or seized bearings
• Spin the shaft by hand to check for resistance
• Remove obstructions or replace worn components before restarting

If left unresolved, the overload relay keeps tripping until the root cause is fixed.

Cause 2: Incorrect Relay Settings

Improper calibration is another common reason. Each relay must be set to the motor’s full-load amperage (FLA). If the setting is too low, the relay nuisance-trips during normal operation.

Troubleshooting:

• Check the relay dial against the motor’s FLA on its nameplate.
• Adjust the setting to match recommended levels.
• Confirm that the trip class overload relay is correct for your application.

Some applications require slower trip curves to handle start-up surges. Using the wrong setting can create more downtime than protection.

Cause 3: Electrical Supply Issues

Unstable power supply conditions often cause overload relay tripping even when the motor is mechanically sound.

• Low voltage: Motors draw more current to maintain torque, overheating quickly.
• Phase imbalance: Uneven current distribution across phases increases the load on one winding.
• Single-phasing: Loss of a phase causes the remaining two to overload.

Troubleshooting:

• Measure voltage at the motor terminals. It should be within ±10% of the nameplate rating.
  Use a clamp meter to check current balance across all three phases.
• Correct wiring faults or consult your power utility if supply instability persists.

Cause 4: Environmental Conditions

Operating conditions can accelerate causes of overload relay tripping. Older thermal relays are especially sensitive to high ambient temperatures or contaminated enclosures.

Troubleshooting:

• Ensure the control panel has adequate cooling and ventilation.
• Clean out dust, dirt, or debris around the relay.
• If the motor operates in consistently hot conditions, consider using ambient-compensated relays for accuracy.

Even a well-calibrated relay may nuisance-trip if exposed to extreme heat or dirty environments.

Cause 5: Relay or Wiring Fault

Sometimes the relay itself is to blame. Worn contacts, faulty wiring, or internal damage can trigger an overload relay trip with no apparent load problem.

Troubleshooting:

• Look for burn marks, melted plastic, or cracked housings.
• Tighten loose or corroded connections.
• Test continuity using a multimeter; replace the relay if readings are inconsistent.

Related: How to Safely Reset an Overload Relay on a Three-Phase Motor

Special Case: Fridge Overload Relay Tripping

Appliance motors face unique stresses. If you notice fridge overload relay tripping, the likely culprits are:

• Dirty condenser coils restricting airflow
• Faulty compressor motor or start relay
• Low voltage or loose wiring
• Refrigerant issues causing overheating
  

Start by cleaning the coils and checking airflow. If the compressor still overheats, the start relay or motor may need replacement.

What Is Trip Class in Overload Relay?

The overload relay trip class defines how quickly the relay responds to current spikes. It’s measured at six times the motor’s rated current.

• Class 10: Trips in 10 seconds or less — ideal for sensitive motors.
• Class 20: Trips in 20 seconds — common for standard industrial use.
  Class 30: Trips in 30 seconds — suited for heavy-duty loads with long startups.

Expert Troubleshooting Support

Even with these checks, diagnosing persistent causes of overload relay tripping can be complex. Simply Buy’s technical support team offers remote diagnostic assistance, helping engineers pinpoint issues without needing on-site expertise. This service is especially valuable in Africa and Southeast Asia, where access to skilled technicians can be limited.

Final Thoughts

Frequent overload relay tripping signals either a problem with the motor, the relay, or the supply. By addressing the five causes above, you’ll reduce downtime and protect your investment.

If your overload relay keeps tripping, don’t just reset it. Find the cause, verify the trip class, and confirm the relay is genuine.

At Simply Buy, we don’t just supply ABB, Siemens, and Schneider relays. We stand behind them. Our after-sales services include:

• Remote technical consultation for troubleshooting
• Guidance on choosing the right relay and trip class
• Fast replacements from global warehouses
• Guaranteed authenticity with refund assurance

Low-quality relays are a frequent cause of false trips. Every relay from Simply Buy is 100% authentic, backed by a no-questions-asked refund service for quality issues. This is particularly valued by quality-conscious buyers in Australia. Contact us to learn more about our products.