NEC ground-wire-chart

NEC Ground Wire Size Chart - Complete Grounding Reference

Complete code requirements, compliance guidance, and professional analysis

Code Requirements Summary

This comprehensive ground wire sizing chart combines NEC Table 250.66 (grounding electrode conductors) and Table 250.122 (equipment grounding conductors) to provide a complete reference for all grounding conductor sizing requirements.

Professional Requirements

  • Use Table 250.66 to size grounding electrode conductors based on largest service entrance conductor
  • Use Table 250.122 to size equipment grounding conductors based on overcurrent device rating
  • Distinguish between grounding electrode conductors and equipment grounding conductors
  • Apply proper sizing for copper vs. aluminum grounding conductors
  • Consider parallel conductor installations and proportional sizing requirements
  • Ensure grounding conductors meet minimum size requirements even when circuits are upsized

Technical Explanation

The NEC ground wire size chart encompasses two critical tables: Table 250.66 for grounding electrode conductors that connect the electrical system to grounding electrodes, and Table 250.122 for equipment grounding conductors that provide fault current paths. Grounding electrode conductors are sized based on the service entrance conductor size because they must handle system fault currents. Equipment grounding conductors are sized based on the overcurrent device rating because they must carry fault currents until the protective device operates. Understanding which table applies to each situation is crucial for proper grounding system design.

Industry Applications

Service entrance grounding conductor selection for residential and commercial installations
Equipment grounding conductor sizing for branch circuits and feeders
Industrial grounding system design and specification
Solar and renewable energy grounding conductor requirements
Electrical service upgrade grounding conductor sizing
Grounding system troubleshooting and code compliance verification

Compliance Analysis Tool

Professional Resources

NEC 2023 State Adoption Status

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Related Code Requirements

NEC 250.66->
NEC 250.122->
NEC 250.24->

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Important Disclaimers

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.

Jurisdiction Variations:Code requirements vary significantly by location. Always consult local electrical codes, amendments, and Authority Having Jurisdiction (AHJ) requirements.

No Warranty:This tool is provided for informational purposes only. Code Buddy makes no warranties regarding accuracy, completeness, or suitability for specific applications.

Professional Support: For complex installations or code interpretations, consult with Code Buddy's expert AI system or licensed electrical professionals.