How to Reset a Motor Protection Breaker: Step-by-Step Guide & Troubleshooting Tips

A motor protection breaker (MPCB) is a critical component in safeguarding industrial motors from damage caused by electrical faults.

Whether you’re dealing with overloads, short circuits, or phase failures, knowing how to properly reset your MPCB can minimize downtime and prevent costly repairs.

In this guide, we’ll walk you through the reset process, troubleshoot common issues, and explain when it’s time to upgrade your equipment.

Safety First: Precautions Before Resetting

⚠️ Never skip these steps!

1. Power Down: Disconnect the main power supply and follow lockout/tagout (LOTO) procedures.
2. Wear PPE: Use insulated gloves and safety goggles.
3. Inspect the Environment: Check for moisture, exposed wires, or flammable materials nearby.、

Step-by-Step Reset Procedure

Step 1: Identify the Trip Cause

Most MPCBs display fault indicators:

• Overload: Red flag or thermal trip indicator (common in Schneider GV2 models).
• Short Circuit: Magnetic trip marker (e.g., Siemens 3RV series).
• Phase Loss: Flashing LED on advanced MPCBs.

Step 2: Isolate the Circuit

• Turn off the upstream power switch.
• Verify the motor has completely stopped.

Step 3: Reset the Breaker

Manual Reset Types:

• Push the handle firmly to OFF, then back to ON (common in traditional MPCBs).
• Press the dedicated reset button (e.g., ABB MS116 series).

Automatic Reset Types:

• Wait 5–10 minutes for the bimetal strip to cool before reactivating.

Step 4: Restore Power & Test

• Gradually restore power and monitor the motor startup.
• If the breaker trips again, proceed to troubleshooting.

Common Causes of MPCB Tripping

Overloads

• Causes: Motor overcurrent due to mechanical jams or incorrect sizing.
• Fix: Adjust the thermal relay settings or upgrade to a higher-rated MPCB. Explore our UL-certified MPCB range for precise current ratings.

Short Circuits

• Causes: Damaged insulation or loose connections.
• Fix: Use a multimeter to test line-to-ground resistance. Replace charred components.

Phase Imbalance/Loss

• Causes: Faulty contactors or unstable grid voltage.
• Fix: Install a phase monitoring relay.

Troubleshooting Persistent Tripping

Checklist:

• Measure motor current with a clamp meter (e.g., Fluke 374).
• Clean dust from breaker contacts using compressed air.
• Verify the MPCB’s tripping curve (e.g., Class 10 for pumps, Class 20 for heavy machinery).

Still unresolved? Contact our support team for a free consultation.

Preventive Maintenance Tips

Quarterly Inspections:

• Tighten terminal screws.
• Test trip functionality using the “TEST” button.

Annual Calibration:

• Recalibrate thermal and magnetic trip units to ensure accuracy.
• Upgrade to smart MPCBs with remote monitoring—browse our latest models.

When to Replace Your Motor Protection Breaker

Replace your MPCB if:

• It trips repeatedly without apparent cause (internal damage).
• The casing shows cracks or discoloration (overheating).
• Your motor’s current exceeds the breaker’s rating (e.g., after equipment upgrades).

Why Choose zk-ele.com?

• Wide Range: From 1A to 630A, compliant with IEC/UL standards.
• Fast Delivery: Global shipping with 24/7 technical support.
• Custom Solutions: Tailored MPCBs for HVAC, pumps, and CNC machines.

Conclusion

Resetting a motor protection breaker is straightforward if done safely and systematically. However, recurring faults often signal deeper issues or aging equipment.

For reliable, certified replacements, trust zk-ele.com—your partner in industrial electrical safety.

Need Help?

• Download our free MPCB Selection Guide.
• Email us at support@zk-ele.com for personalized advice.