Understanding NEC 250.118: Approved Equipment Grounding Conductors

NEC 250.118: Types of Equipment Grounding Conductors

Overview

The equipment grounding conductor installed alongside or enclosing the circuit conductors must adhere to specific types as outlined in the NEC. These ensure the safety and effectiveness of the grounding system.

Note: Refer to 250.2 for the definition of an effective ground-fault current path.

Types of Equipment Grounding Conductors

• (1) Metal Conductors

  Includes copper, aluminum, or copper-clad aluminum conductors, which can be solid or stranded, insulated, covered, or bare, and shaped as a wire or busbar.

• (2) Rigid Metal Conduit (RMC)

  Provides a durable and effective grounding path.

• (3) Intermediate Metal Conduit (IMC)

  A suitable metal pathway for grounding conductors.

• (4) Electrical Metallic Tubing (EMT)

  Offers grounding and physical protection for circuit conductors.

• (5) Listed Flexible Metal Conduit (FMC)

  Permitted when:

  • Terminated in listed fittings.
  • Overcurrent devices rated at ≤ 20 amperes protect the circuit conductors.
  • Total length of all flexible conduits in the ground path does not exceed 1.8 m (6 ft).
  • An additional equipment grounding conductor is installed for flexible connections.

• (6) Listed Liquidtight Flexible Metal Conduit (LFMC)

  Allowed under these conditions:

  • Terminated in listed fittings.
  • For trade sizes 3⁄8 to 1⁄2, conductors protected by ≤ 20-ampere devices.
  • For trade sizes 3⁄4 to 1-1⁄4, conductors protected by ≤ 60-ampere devices.
  • Total flexible conduit length in the grounding path ≤ 1.8 m (6 ft).
  • Additional equipment grounding conductor is required for flexible installations.

• (7) Flexible Metallic Tubing (FMT)

  Permitted when:

  • Circuit conductors protected by ≤ 20-ampere devices.
  • Grounding path length ≤ 1.8 m (6 ft).

• (8) Armor of Type AC Cable

  Grounding permitted as outlined in 320.108.

• (9) Copper Sheath of Mineral-Insulated Cable (Type MI)

  Provides effective grounding.

• (10) Type MC Cable

  Must be listed and identified for grounding:

  • Includes interlocked metal tape or corrugated metallic sheaths.

• (11) Cable Trays

  Permitted as per 392.3 and 392.7.

• (12) Cablebus Framework

  Allowed under 370.3.

• (13) Listed Electrically Continuous Metal Raceways

  Includes raceways and listed auxiliary gutters.

• (14) Listed Surface Metal Raceways

  Specifically listed for grounding purposes.