Electrician Grounding and Bonding 2

Question 1

For a separately derived system such as a step-down transformer, where must the system bonding jumper be installed per NEC 250.30(A)(1)?

Accepted Answer

At the source of the separately derived system

Answer

NEC 250.30(A)(1) requires the system bonding jumper to be installed at the source of the separately derived system to establish the neutral-to-ground bond.

Question 2

Per NEC 250.52(A)(3), a concrete-encased grounding electrode must contain at least how much bare copper conductor or rebar encased in the concrete?

Accepted Answer

20 feet

Answer

NEC 250.52(A)(3) requires at least 20 feet of bare copper conductor or rebar encased within a concrete foundation to qualify as a concrete-encased electrode.

Question 3

Per NEC 250.56, if a single ground rod electrode has a resistance to earth exceeding what value, a supplemental electrode must be added?

Accepted Answer

25 ohms

Answer

NEC 250.56 requires a supplemental grounding electrode whenever a single rod electrode has a measured resistance exceeding 25 ohms.

Question 4

Which NEC table is used to determine the minimum size of a grounding electrode conductor based on the size of the service entrance conductors?

Accepted Answer

Table 250.66

Answer

NEC Table 250.66 cross-references service entrance conductor size to the minimum required grounding electrode conductor size.

Question 5

What is the minimum conductor size required for a ground ring grounding electrode per NEC 250.52(A)(4)?

Accepted Answer

2 AWG bare copper

Answer

NEC 250.52(A)(4) requires a ground ring to consist of at least 2 AWG bare copper conductor encircling the building or structure.

Electrician Practice Test

Electrician Practice Test

Electrician Grounding and Bonding 2