Grounding Systems Flashcards

What is the minimum burial depth for a ground ring conductor installed in soil under the NEC?

Answer: 18 inches

NEC 250.52(A)(4) requires a ground ring to be buried at least 30 inches (762 mm) below the surface of the earth — but the conductor within that ring must be at least 2 AWG and buried no less than 2.5 feet; the 30-inch rule applies.

Which NEC article primarily governs grounding and bonding requirements?

Answer: Article 250

NEC Article 250 covers all requirements for grounding and bonding of electrical systems and equipment.

A separately derived system's grounding electrode conductor must be connected at which point?

Answer: At the source of the separately derived system

Per NEC 250.30, the grounding electrode conductor for a separately derived system must connect at the source — such as the secondary of a transformer.

What term describes the low-impedance path provided to facilitate the operation of overcurrent devices during a ground fault?

Answer: Effective ground-fault current path

An effective ground-fault current path is a permanent, low-impedance electrically conductive path that facilitates overcurrent device operation during a ground fault.

When is a main bonding jumper required?

Answer: At the service entrance to bond the neutral to the equipment ground

The main bonding jumper connects the grounded conductor (neutral) to the equipment grounding conductor and service equipment enclosure at the service entrance.

Which of the following is NOT an acceptable grounding electrode under NEC 250.52?

Answer: Copper pipe used for gas supply

Gas supply piping must never be used as a grounding electrode because it creates a fire and explosion hazard.

What minimum size copper conductor is required for a grounding electrode conductor when the service entrance conductors are 3/0 AWG copper?

Answer: 4 AWG

Per NEC Table 250.66, service entrance conductors of 2/0–3/0 AWG require a 4 AWG copper grounding electrode conductor.