How to Test a Circuit Breaker

Knowing how to test a circuit breaker can help determine whether a breaker is functioning properly or needs to be replaced. While circuit breakers are designed to provide years of reliable protection, they can eventually wear out due to age, repeated tripping, electrical overloads, or internal mechanical failure.

This guide explains several methods for testing residential and commercial circuit breakers and when it's time to replace a faulty breaker.

Why Test a Circuit Breaker?

A properly functioning circuit breaker protects your electrical system by automatically shutting off power during overloads or short circuits. If a breaker fails to trip when it should—or trips too easily—it can create safety hazards or unnecessary interruptions.

Common reasons to test a circuit breaker include:

Breaker frequently trips without an obvious cause
Breaker will not reset
Lights flicker or lose power intermittently
Burning smell or signs of overheating
Electrical panel is older or contains obsolete breakers

Step 1: Perform a Visual Inspection

Before using any test equipment, inspect the breaker for visible signs of damage.

Burn marks or discoloration
Cracked or damaged housing
Loose handle
Corrosion
Melted plastic

If any of these conditions are present, the breaker should be evaluated and likely replaced.

Step 2: Test the Breaker Operation

Switch the breaker completely OFF and then back ON. A properly functioning breaker should have a firm, positive action.

If the handle feels loose, won't stay in the ON position, or will not reset after tripping, the breaker may be defective.

Learn more in our guide on Circuit Breaker Not Resetting.

Step 3: Measure Voltage with a Multimeter

Using a properly rated multimeter, qualified individuals can verify whether voltage is present at the breaker output.

Verify voltage entering the breaker.
Verify voltage leaving the breaker.
Compare readings to the expected circuit voltage.

Warning: Testing energized electrical equipment should only be performed by qualified individuals using appropriate personal protective equipment (PPE) and following all applicable electrical safety procedures.

Step 4: Check for Excessive Heat

A breaker that runs unusually hot may indicate:

Loose electrical connections
Overloaded circuits
Internal breaker failure
Damaged bus bar connections

Electricians often use infrared thermography to identify overheating breakers before failure occurs.

Common Signs of a Bad Circuit Breaker

A circuit breaker may need replacement if you notice:

Frequent nuisance tripping
Breaker will not reset
Visible damage
Burning odor
Buzzing or humming sounds
Breaker feels unusually hot
Intermittent power loss

Read more in our guide on Signs of a Bad Circuit Breaker.

Should You Repair or Replace the Breaker?

Most molded-case circuit breakers are not repaired in the field. If testing indicates that a breaker has failed, replacing it with a properly compatible breaker is usually the safest and most reliable solution.

Electrical Supplies Unlimited stocks a large inventory of new, used, surplus, and obsolete replacement breakers from leading manufacturers.

Finding the Correct Replacement Breaker

Before purchasing a replacement, verify:

Manufacturer
Model number
Amperage rating
Voltage rating
Panel compatibility

Helpful resources include our Circuit Breaker Identification Guide and Circuit Breaker Compatibility Guide.

Need a Replacement Circuit Breaker?

Electrical Supplies Unlimited has been supplying replacement circuit breakers for over 40 years. We stock thousands of new, used, surplus, obsolete, and hard-to-find breakers from manufacturers including Siemens, Square D, Eaton, Cutler Hammer, GE, Federal Pacific (FPE), Challenger, Zinsco, Bryant, and many others.

If you need assistance identifying or replacing a faulty breaker, our knowledgeable staff can help you find the right solution.