Electrician Services and Distribution 1 — Questions and Answers
Question 1: What is the minimum ampacity required for a service to a single-family dwelling per the NEC?
- 60 amps
- 100 amps (Correct answer)
- 150 amps
- 200 amps
Correct answer: 100 amps
NEC 230.79(C) requires a minimum 100-ampere service for single-family dwellings.
Question 2: What is the purpose of a main disconnect in a service entrance panel?
- To step down voltage from utility
- To provide a means to disconnect all power to the premises (Correct answer)
- To filter harmonics from the utility
- To measure power consumption
Correct answer: To provide a means to disconnect all power to the premises
The main disconnect provides a single means to de-energize all branch circuits and feeders within the building.
Question 3: What is the difference between a service lateral and a service drop?
- A lateral carries higher voltage than a drop
- A lateral is underground; a drop is overhead (Correct answer)
- A lateral uses aluminum wire; a drop uses copper
- There is no difference
Correct answer: A lateral is underground; a drop is overhead
A service lateral refers to underground service conductors, while a service drop refers to overhead conductors from the utility.
Question 4: What is the maximum number of disconnecting means permitted at a service entrance per the NEC?
- 2
- 4
- 6 (Correct answer)
- 8
Correct answer: 6
NEC 230.71 allows a maximum of six disconnects at a single service entrance location.
Question 5: What type of grounding electrode is considered the most effective?
- Ground rod
- Concrete-encased electrode (Ufer ground) (Correct answer)
- Metal underground water pipe
- Building steel
Correct answer: Concrete-encased electrode (Ufer ground)
The concrete-encased electrode (Ufer ground) is considered highly effective because the moisture in concrete provides excellent soil contact.
Question 6: What is the minimum length for a ground rod?
- 4 feet
- 6 feet
- 8 feet (Correct answer)
- 10 feet
Correct answer: 8 feet
NEC 250.52(A)(5) requires a ground rod to be at least 8 feet long when driven into the earth.
Electrician Services and Distribution 1
What is the minimum ampacity required for a service to a single-family dwelling per the NEC?