NEC 250.122

Equipment Grounding Conductor Size Chart - Table 250.122

Complete code requirements, compliance guidance, and professional analysis

Code Requirements Summary

NEC 250.122 and Table 250.122 specify the minimum size requirements for equipment grounding conductors based on the rating of the overcurrent protective device ahead of the equipment being protected.

Professional Requirements

  • Size equipment grounding conductors per Table 250.122 based on overcurrent device rating
  • Install equipment grounding conductors with all circuit conductors in same raceway or cable
  • Use copper or aluminum equipment grounding conductors as specified in installation
  • Increase equipment grounding conductor size when circuit conductors are upsized for voltage drop
  • Run equipment grounding conductors in parallel when circuit conductors are paralleled

Technical Explanation

Table 250.122 provides the minimum cross-sectional area for equipment grounding conductors based on the ampere rating of the overcurrent protective device. The table ensures adequate current-carrying capacity to safely carry fault currents back to the source during ground fault conditions. Equipment grounding conductors create the low-impedance path necessary for protective devices to operate quickly and clear faults. The sizing is based on the overcurrent device rating, not the actual load, because the grounding conductor must handle the full fault current that the breaker or fuse is designed to interrupt.

Industry Applications

Sizing equipment grounding conductors for branch circuits in residential and commercial installations
Determining ground wire size for motor circuits and equipment feeders
Calculating equipment grounding conductor requirements for parallel conductor installations
Specifying grounding conductors for electrical panels, subpanels, and distribution equipment
Industrial equipment grounding for machinery and control systems
Service equipment and separately derived system grounding conductor sizing

Compliance Analysis Tool

Professional Resources

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Related Code Requirements

NEC 250.118->
NEC 250.120->
NEC 250.66->

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