Free E2 Grounding and Bonding Questions and Answers 1

Question 1

What is the minimum size copper grounding electrode conductor (GEC) required for a service with 500 kcmil copper ungrounded service-entrance conductors?

Accepted Answer

1/0 AWG

Answer

NEC Table 250.66 is used to size the grounding electrode conductor based on the size of the service-entrance conductors. For 500 kcmil copper conductors, the table requires a minimum GEC size of 1/0 AWG copper. This ensures the GEC can safely conduct fault current to the grounding electrode.

Question 2

A grounding electrode conductor is connected only to a concrete-encased electrode (Ufer ground). What is the largest size copper conductor required for this connection?

Accepted Answer

4 AWG

Answer

According to NEC 250.66(B), if a grounding electrode conductor is connected solely to a concrete-encased electrode, it is not required to be larger than 4 AWG copper. This is because the concrete encasement provides protection and limits the potential fault current the conductor would need to carry.

Question 3

Which of the following, if present and meeting the required specifications, MUST be used as part of the grounding electrode system for a commercial building?

Accepted Answer

A metal underground water pipe

Answer

NEC 250.52(A) lists the items that are required to be used as grounding electrodes if they are present. A metal underground water pipe in direct contact with the earth for 10 feet or more is listed in 250.52(A)(1) and must be part of the grounding electrode system. Interior piping and gas piping are specifically prohibited or restricted for use as electrodes.

Question 4

What is the minimum size copper equipment grounding conductor (EGC) required for a branch circuit protected by a 400-ampere circuit breaker?

Accepted Answer

3 AWG

Answer

NEC Table 250.122 sizes the equipment grounding conductor based on the rating of the overcurrent protective device. For a 400-ampere OCPD, the table specifies a minimum EGC size of 3 AWG copper. The EGC provides a low-impedance path for fault current to facilitate the opening of the OCPD.

Question 5

On the load side of the service disconnect, which conductor is generally prohibited from being used to ground the metal frame of equipment?

Accepted Answer

The grounded conductor

Answer

NEC 250.142(B) prohibits using the grounded circuit conductor (neutral) for grounding non-current-carrying metal parts of equipment on the load side of the service disconnecting means. Doing so would allow normal neutral current to flow on equipment frames, creating a shock hazard. A separate equipment grounding conductor must be used.

(E2) E2 Commercial Electrical Inspector Practice Test

(E2) E2 Commercial Electrical Inspector Practice Test

Free E2 Grounding and Bonding Questions and Answers 1