Licensed Electrical Contractor Licensed Electrical Contractor Grounding and Bonding Questions and Answers 2

Question 1

What is the minimum size copper grounding electrode conductor required for a 400-amp service per NEC Article 250?

Accepted Answer

1/0 AWG

Answer

2/0 AWG

Answer

3/0 AWG

Answer

4/0 AWG

Question 2

When using a concrete-encased electrode (Ufer ground), what is the minimum length of bare copper conductor that must be encased in the concrete?

Accepted Answer

20 feet

Answer

10 feet

Answer

30 feet

Answer

40 feet

Question 3

What is the primary purpose of equipment bonding jumpers in an electrical system?

Accepted Answer

To ensure electrical continuity and conductivity between metal parts

Answer

To carry normal operating current

Answer

To provide a path for neutral current

Answer

To reduce voltage drop in branch circuits

Question 4

Per NEC 250.104, what metal piping system within a building must be bonded to the electrical service grounding system?

Accepted Answer

Interior metal water piping

Answer

Only copper water piping

Answer

Only gas piping

Answer

All HVAC ductwork regardless of material

Question 5

What is the maximum resistance to ground allowed for a single rod, pipe, or plate grounding electrode before a supplemental electrode is required?

Accepted Answer

25 ohms

Answer

5 ohms

Answer

10 ohms

Answer

15 ohms

Question 6

In a separately derived system such as a transformer, where must the bonding jumper be installed?

Accepted Answer

At the source of the separately derived system

Answer

At the main service panel only

Answer

At any convenient point in the system

Answer

At the nearest subpanel downstream