Code Reference
ElectricalNEC 2023

Section 240.6/Standard Ampere Ratings

NEC 240.6 lists the standard ampere ratings for fuses and circuit breakers, determining available overcurrent device sizes.

What this section requires

The standard ampere ratings for fuses and inverse time circuit breakers are: 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, 200, 225, 250, 300, 350, 400, 450, 500, 600, 700, 800, 1000, 1200, 1600, 2000, 2500, 3000, 4000, 5000, and 6000 amperes. Additional standard ratings for fuses include 1, 3, 6, and 10 amperes.

Why this section exists

Standard ratings ensure that overcurrent devices are commercially available in consistent sizes across manufacturers. This allows designers to specify circuits knowing that the breaker or fuse size exists and is interchangeable. Non-standard sizes would require custom equipment, increasing cost and complicating replacement.

What plan reviewers look for

Plan reviewers check that every breaker and fuse size on panel schedules and one-line diagrams is a standard rating from 240.6. Non-standard sizes (55A, 65A, 85A) are flagged as errors. Reviewers also verify that the next-standard-size-up rule (240.4(B)) is applied correctly when used.

Common violations

Non-standard breaker size specified
A panel schedule shows a 55-amp or 65-amp breaker. These are not standard ratings per 240.6. The designer likely intended 60 or 70 amps.
Next size up rule misapplied
Using the next standard size up per 240.4(B) on a multi-outlet receptacle circuit, where the exception does not apply. The next-size-up rule is limited to specific conditions.
Compliance tip
Cross-check every breaker and fuse size on the panel schedule against the standard ratings. When a load calculation results in a non-standard value, round up to the next standard rating and verify the conductor ampacity supports it.

Related NEC requirements

Section 240.4 covers conductor protection and the next-standard-size-up rule. Section 210.3 defines branch circuit ratings based on the overcurrent device. Section 240.83 covers marking requirements for circuit breakers.

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Related sections

210.3Branch Circuit Rating ClassificationNEC 2023215.2Feeder Conductor SizingNEC 2023240.4Protection of ConductorsNEC 2023