NEC 240.6

Standard Ampere Ratings - Breaker & Fuse Sizes Chart

Complete code requirements, compliance guidance, and professional analysis

Code Requirements Summary

NEC 240.6 establishes the standard ampere ratings for fuses and circuit breakers, defining the specific sizes available for overcurrent protection devices in electrical installations.

Professional Requirements

  • Use only standard ampere ratings listed in NEC 240.6 for overcurrent protection devices
  • Select proper breaker or fuse size based on conductor ampacity and load calculations
  • Verify overcurrent device rating does not exceed conductor ampacity per NEC 240.4
  • Consider ambient temperature corrections when sizing overcurrent protection
  • Ensure proper coordination between upstream and downstream protective devices

Technical Explanation

NEC 240.6 provides the standardized ampere ratings that manufacturers must follow for fuses and circuit breakers. These standard sizes ensure consistency across the electrical industry and proper coordination between different manufacturers' equipment. The ratings progress in a logical sequence that accommodates most electrical load requirements while maintaining adequate protection. Custom or non-standard ratings are not permitted except for specific applications outlined elsewhere in the Code.

Industry Applications

Residential panel breaker selection for branch circuits and feeders
Commercial electrical system overcurrent protection sizing
Industrial motor control center breaker specification
Service entrance equipment overcurrent device selection
Electrical panel upgrades and retrofits
Load center and panelboard equipment specification

Compliance Analysis Tool

Professional Resources

NEC 2023 State Adoption Status

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Related Code Requirements

NEC 240.4->
NEC 240.21->
NEC 110.9->

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Copyright Notice:The National Electrical Code (NEC) is copyrighted by the National Fire Protection Association (NFPA). This page provides professional analysis and interpretation for educational purposes only. For official code text, consult NFPA 70.

Professional Use Notice:This analysis tool provides technical guidance based on standard NEC requirements. Local codes, amendments, and AHJ interpretations may supersede national standards.

Compliance Verification:This tool offers preliminary compliance assessment. Final code compliance must be verified by licensed professionals and local inspectors.

Professional Responsibility:Licensed electricians remain fully responsible for code compliance, safety, and proper installation practices regardless of tool recommendations.

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