Grounding and Bonding Flashcards

In a commercial installation, structural steel of a building can serve as a grounding electrode when it is connected to at least how many ground rods?

Answer: Two ground rods

NEC 250.52(A)(2) permits building structural steel as a grounding electrode if it is connected to at least two driven ground rods.

Equipment grounding conductors installed in conduit must be sized based on which NEC table?

Answer: Table 250.122

NEC Table 250.122 is used to determine the minimum size equipment grounding conductor based on the rating of the overcurrent device.

What is the NEC requirement for bonding metal gas piping in a commercial building?

Answer: Bond to the electrical service grounding electrode system

NEC 250.104(B) requires metal gas piping to be bonded to the electrical service grounding electrode system to prevent dangerous voltage differences.

When a grounding electrode conductor is installed in ferrous metal conduit, what additional requirement applies?

Answer: Both ends of the conduit must be bonded to the GEC

NEC 250.64(E) requires bonding both ends of ferrous metal conduit enclosing a GEC to prevent induced currents and choke effects.

What is the maximum distance from the point of entrance that a metal underground water pipe must be bonded?

Answer: 5 feet

NEC 250.68(C)(1) requires the grounding electrode conductor connection to a water pipe electrode to be made within 5 feet of the point of entry into the building.

A load-side bonding jumper installed inside a raceway must be sized per which NEC provision?

Answer: NEC Table 250.122

Load-side bonding jumpers within raceways are sized the same as equipment grounding conductors using NEC Table 250.122.

Which grounding electrode type has the highest priority (must be used when present) per NEC 250.50?

Answer: Concrete-encased electrodes

NEC 250.50 requires concrete-encased electrodes (Ufer grounds) to be used when present because they provide superior grounding performance in most soil conditions.