Grounding and Bonding Flashcards
7 cards from real Electrician practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Grounding and Bonding flashcards as text
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)?
Answer: At the source of the separately derived system
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.
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?
Answer: 20 feet
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.
Per NEC 250.56, if a single ground rod electrode has a resistance to earth exceeding what value, a supplemental electrode must be added?
Answer: 25 ohms
NEC 250.56 requires a supplemental grounding electrode whenever a single rod electrode has a measured resistance exceeding 25 ohms.
Which NEC table is used to determine the minimum size of a grounding electrode conductor based on the size of the service entrance conductors?
Answer: Table 250.66
NEC Table 250.66 cross-references service entrance conductor size to the minimum required grounding electrode conductor size.
What is the minimum conductor size required for a ground ring grounding electrode per NEC 250.52(A)(4)?
Answer: 2 AWG bare copper
NEC 250.52(A)(4) requires a ground ring to consist of at least 2 AWG bare copper conductor encircling the building or structure.
At what minimum depth below grade must a ground ring electrode be buried per NEC 250.52(A)(4)?
Answer: 30 inches
NEC 250.52(A)(4) requires the ground ring conductor to be buried at least 30 inches (750 mm) below the earth's surface.
Per NEC 250.53(B), what is the minimum separation required between two ground rod electrodes when more than one is installed?
Answer: 6 feet
NEC 250.53(B) requires ground rods to be spaced at least 6 feet apart so each rod contacts independent soil and resistance zones do not overlap.