What breaker locks should I use for miniature circuit breakers (MCBs)?

Miniature Circuit Breakers (MCBs) are safety locks that prevent short circuits and overcurrents in electrical circuits. Several different MCB types are available – types A, B, C, D, K, and Z –  all of which are designed to respond to the expected power of electrical surges in different settings.

Below are the most commonly used Miniature Circuit Breaker (MCB) lockout devices:


Pin-Out Wide – designed for single- and multi-pole circuit breakers; accommodates up to ⅘” hole spacing.

Pin-In Standard – designed for single- and multi-pole circuit breakers; accommodates up to ½” hole spacing.

Pin-Out Standard – designed for single- and multi-pole circuit breakers; accommodates up to ½" hole spacing.

Tie Bar – designed for single- and multi-pole circuit breakers; best use for circuit breakers with tie bars.

The material provided in this article is for general information purposes only. It is not intended to replace professional/legal advice or substitute government regulations, industry standards, or other requirements specific to any business/activity. While we made sure to provide accurate and reliable information, we make no representation that the details or sources are up-to-date, complete or remain available. Readers should consult with an industrial safety expert, qualified professional, or attorney for any specific concerns and questions.

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