Practical Pitfalls to Avoid for All Types of Circuit Breakers: Steer Clear of 5 Common Electrician Mistakes to Ensure Safe Electricity Use

Last month, an electrician at a manufacturing plant made a seemingly trivial mistake while maintaining a residual current circuit breaker (RCCB): he reversed the ground wire connection without double-checking. Within an hour, a leakage fault occurred in the workshop, but the RCCB failed to trip, causing an electric shock to a worker and forcing the plant to shut down for maintenance. This incident is not an exception—more than 60% of circuit breaker failures are caused by improper operations, which not only increase maintenance costs but also pose serious safety hazards. Today, we’ll break down 5 common mistakes electricians make when working with all types of circuit breakers, helping you avoid errors and ensure safe electricity use.

The core hazard of improper operation lies in its invisibility and destructiveness. Many minor mistakes, such as loose terminal connections or random parameter adjustments, may not cause immediate failures but will gradually damage the circuit breaker’s performance, leading to overload, short circuit, or leakage accidents over time. Different types of circuit breakers (Air Circuit Breakers - ACB, Molded Case Circuit Breakers - MCCB, Miniature Circuit Breakers - MCB, Residual Current Circuit Breakers - RCCB,Residual Current Breaker with Overcurrent protection--RCBO) have different structures and functions, so the hazards and avoidance methods of improper operations also vary.

Here are 5 common improper operations electricians often make with all types of circuit breakers, along with professional guidance to avoid them:

Mistake 1 (ACB): Blindly manual closing without cutting off the load, leading to contact burnout, short circuit, and even arc injury. Guidance: Follow the correct closing procedure for ACB in high-load scenarios—cut off the load first, check the circuit for faults, and then close the switch to avoid direct operation under load.

Mistake 2 (MCCB): Frequent manual opening and closing, resulting in wear of the operating mechanism, reduced breaking capacity, and shortened service life. Guidance: Clarify the reasonable frequency of MCCB opening and closing—avoid frequent manual operations unless necessary, and operate in accordance with the equipment manual.

Mistake 3 (MCB): Randomly replacing MCB with a higher rated current, leading to insensitive protection and equipment burnout due to failure to trip during overload. Guidance: Select MCB rated current according to the actual load—never replace it with a larger specification arbitrarily, as it will lose the overload protection function.

Mistake 4 (RCCB/RCBO):

I.Common Incorrect Operations

General Errors:

1.Reverse/wrong connection of neutral and live wires, damaging the residual current detection circuit;

2.Failure to perform simulated residual current tests via the test button for a long time, leading to undetected invalidation of protection functions;

3.Unauthorized short-circuiting of the residual current protection module to forcibly disable core protection.

RCCB-Specific Errors:

1.Standalone use for overload/short-circuit protection (RCCBs have no overcurrent protection function);

2.Incorrect mounting sequence when paired with circuit breakers (installing RCCB before the circuit breaker).

RCBO-Specific Errors:

1.Selection only by residual current parameters while ignoring matching the rated current of loads, causing frequent overcurrent tripping;

2.Using it merely as a pure residual current protection device and failing to utilize its integrated overcurrent protection function, resulting in circuit redundancy from redundant circuit breaker pairing.