Code & NEC
How is an equipment grounding conductor sized?
Start with the overcurrent device, then account for conductor upsizing and local requirements.
Begin with the circuit overcurrent device, then evaluate conductor upsizing, parallel paths, raceway suitability, and equipment instructions.
Inputs to collect
- Overcurrent-device type and rating.
- Wiring method and whether the raceway is intended to serve as the grounding path.
- Any ungrounded-conductor upsizing for voltage drop or another reason.
- Parallel raceways, flexible sections, and termination hardware.
Decision path
- Find the baseline equipment-grounding-conductor requirement in the adopted edition.
- Evaluate proportional adjustment when ungrounded conductors are increased in size.
- Confirm each parallel raceway or cable has the required fault-current path.
Common mistakes
- Sizing from normal load current instead of the protective device.
- Ignoring an upsized phase conductor.
- Assuming every raceway connection provides an effective fault-current path.
Verification
- Inspect continuity, fittings, bonding points, terminations, and torque; document the protective-device rating and sizing basis.