Licensed Electrical Contractor FREE Licensed Electrical Contractor Grounding and Bonding Questions and Answers 3

Question 1

What is the minimum burial depth required for a ground rod driven vertically into the earth per NEC 250.53?

Accepted Answer

8 feet

Answer

NEC 250.53(G) requires ground rods to be driven to a minimum depth of 8 feet in contact with the earth.

Question 2

When using rigid metal conduit as an equipment grounding conductor, which of the following fittings is NOT acceptable for bonding at service equipment?

Accepted Answer

Standard locknuts

Answer

NEC 250.92(B) does not permit standard locknuts alone for bonding at service equipment; bonding locknuts, bushings, or threaded connections are required.

Question 3

What is the maximum length of a bonding jumper for an interior metal water piping system before it must be sized per NEC Table 250.66?

Accepted Answer

There is no length limit; it is always sized per Table 250.66

Answer

The bonding conductor for interior metal water piping is always sized per NEC Table 250.66 based on the service-entrance conductor size, regardless of length.

Question 4

A concrete-encased electrode (Ufer ground) must contain at least how many feet of reinforcing steel or bare copper conductor encased in concrete?

Accepted Answer

20 feet

Answer

NEC 250.52(A)(3) requires a minimum of 20 feet of electrically conductive reinforcing steel or bare copper conductor encased in at least 2 inches of concrete.

Question 5

When separately derived systems supply a building, what determines the sizing of the system bonding jumper?

Accepted Answer

The size of the largest derived ungrounded conductor

Answer

Per NEC 250.30(A)(1), the system bonding jumper is sized based on the area of the largest ungrounded conductor using NEC Table 250.66.

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Licensed Electrical Contractor FREE Licensed Electrical Contractor Grounding and Bonding Questions and Answers 3