WiremanMy stuff

Wireman · Grounding and bonding · 2023 NEC ·

Reference

Grounding and bonding

Equipment grounding conductors go by the breaker. Grounding electrode conductors go by the service conductors.

Equipment grounding conductor (EGC)

The green or bare wire that runs with the circuit. Size it from the breaker or fuse protecting the circuit.

A

Breaker or fuse up toCopperAluminum
15 A14 AWG12 AWG
20 A12 AWG10 AWG
60 A10 AWG8 AWG
100 A8 AWG6 AWG
200 A6 AWG4 AWG
300 A4 AWG2 AWG
400 A3 AWG1 AWG
500 A2 AWG1/0 AWG
600 A1 AWG2/0 AWG
800 A1/0 AWG3/0 AWG
1,000 A2/0 AWG4/0 AWG
1,200 A3/0 AWG250 kcmil
1,600 A4/0 AWG350 kcmil
2,000 A250 kcmil400 kcmil
2,500 A350 kcmil600 kcmil
3,000 A400 kcmil600 kcmil
4,000 A500 kcmil750 kcmil
5,000 A700 kcmil1200 kcmil
6,000 A800 kcmil1200 kcmil

Good to know

  • If you upsize the hots for voltage drop, upsize the EGC by the same ratio of area (250.122(B)).
  • Parallel runs: each raceway or cable gets a full-size EGC from this table (250.122(F)).
  • The EGC never has to be bigger than the circuit conductors.
  • Metal raceways like EMT and rigid can serve as the EGC where they're listed and installed for it (250.118).

NEC: Table 250.122, 250.118, 250.122(B), 250.122(F)

Grounding electrode conductor (GEC)

Connects the service neutral and equipment to the electrodes: rods, concrete-encased (Ufer), water pipe, building steel.

What does this GEC go to?

Copper serviceAluminum serviceGEC copperGEC aluminum
2 AWG or smaller1/0 AWG or smaller8 AWG6 AWG
Over 2 AWG to 1/0 AWGOver 1/0 AWG to 3/0 AWG6 AWG4 AWG
Over 1/0 AWG to 3/0 AWGOver 3/0 AWG to 250 kcmil4 AWG2 AWG
Over 3/0 AWG to 350 kcmilOver 250 kcmil to 500 kcmil2 AWG1/0 AWG
Over 350 kcmil to 600 kcmilOver 500 kcmil to 900 kcmil1/0 AWG3/0 AWG
Over 600 kcmil to 1100 kcmilOver 900 kcmil to 1750 kcmil2/0 AWG4/0 AWG
Over 1100 kcmilOver 1750 kcmil3/0 AWG250 kcmil

Good to know

  • A GEC that only goes to ground rods never has to be bigger than 6 AWG copper. To a concrete-encased electrode only, never bigger than 4 AWG copper.
  • Supplemental rod: one rod needs to test 25 Ω or less, or you drive a second one at least 6 ft away.
  • A metal water pipe electrode always needs a supplemental electrode, and the GEC connects within the first 5 ft of pipe inside the building.
  • Keep the GEC continuous, or splice it only with irreversible compression or exothermic connections.

NEC: Table 250.66, 250.52, 250.53(A)(2), 250.53(D)(2), 250.68(C)(1), 250.64(C)

Bonding basics