What is the function of an equipment grounding conductor and how is it sized?

What is the function of an equipment grounding conductor and how is it sized?

• A. Carries load current during normal operation and is sized by voltage rating.
• B. Connects the system to the earth electrode.
• C. Provides fault current return path to ground; sized according to NEC tables based on overcurrent device rating.
• D. Used for bonding metal parts only; ignore NEC.

Answer: (C)

The main idea is safety: an equipment grounding conductor provides a low-impedance path for fault current to return to the source so the overcurrent protective device can trip and clear the fault quickly, keeping exposed parts at a safe potential. It is not meant to carry normal load current—that role is for the hot and neutral conductors—and it connects the equipment’s grounding point to the building’s grounding system so any fault current has a reliable path to earth. Sizing follows the NEC rule that the conductor size is determined by the rating of the overcurrent device protecting the circuit, not by voltage. NEC tables specify the minimum equipment grounding conductor size for each possible device rating (copper or aluminum), ensuring the fault current is ample to trip the breaker. In practice, you’d look up the circuit’s overcurrent device rating and select the corresponding EGC size from the NEC table (for example, a 15A circuit requires at least a 14 AWG copper EGC, a 20A circuit at least 12 AWG, and larger devices require larger conductors).

The main idea is safety: an equipment grounding conductor provides a low-impedance path for fault current to return to the source so the overcurrent protective device can trip and clear the fault quickly, keeping exposed parts at a safe potential. It is not meant to carry normal load current—that role is for the hot and neutral conductors—and it connects the equipment’s grounding point to the building’s grounding system so any fault current has a reliable path to earth.

Sizing follows the NEC rule that the conductor size is determined by the rating of the overcurrent device protecting the circuit, not by voltage. NEC tables specify the minimum equipment grounding conductor size for each possible device rating (copper or aluminum), ensuring the fault current is ample to trip the breaker. In practice, you’d look up the circuit’s overcurrent device rating and select the corresponding EGC size from the NEC table (for example, a 15A circuit requires at least a 14 AWG copper EGC, a 20A circuit at least 12 AWG, and larger devices require larger conductors).