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Electricalaka: breakeraka: CB

Circuit Breaker

In Plain English

A resettable safety switch in your electrical panel that automatically shuts off power when a circuit is overloaded.

Definition

An automatically operated electrical switch designed to protect a circuit from damage caused by excess current resulting from an overload or short circuit. Unlike fuses, circuit breakers can be reset after tripping. They are rated in amperes and interrupt current when that rating is exceeded.

Why It Matters in Bidding

Breakers are counted line by line from the panel schedule, and their type and rating, standard, GFCI, AFCI, or specialty, can swing the electrical material cost noticeably across a project with many devices. Estimators must match each breaker to the spec and code requirement, because substituting a cheaper standard breaker where code requires GFCI or AFCI protection invites a failed inspection, rework, and lost margin.

Example

Taking off a multifamily project, the electrical estimator prices AFCI breakers for the bedroom circuits and GFCI breakers for the kitchen and bath circuits per code, rather than assuming standard breakers throughout.

Related Terms

Electrical PanelBranch CircuitArc Fault Circuit Interrupter (AFCI)Ground Fault Circuit Interrupter (GFCI)

Frequently Asked Questions

A fuse must be replaced after it blows, while a breaker resets. For estimating, modern projects almost always use breakers in panelboards, so the takeoff prices breakers by rating and type from the panel schedule. Fuses still appear in some disconnects and equipment, which estimators capture separately.
GFCI and AFCI breakers cost considerably more than standard breakers, and code dictates where each is required, such as kitchens, baths, and bedrooms. Because a panel can hold dozens of breakers, using the correct mix from the start materially affects the bid and prevents costly substitutions at inspection.
The panel schedules on the electrical drawings list every breaker by circuit, rating, and pole count, and the specifications call out required types like GFCI or AFCI. Estimators tally directly from these documents, cross-checking against the one-line diagram so no panel or feeder breaker is missed.

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