PC Load Calculations and Service Entrance 2 — Questions and Answers
Question 1: The optional calculation method for a one-family dwelling load is located in which NEC section?
- NEC 220.82 (Correct answer)
- NEC 220.83
- NEC 220.84
- NEC 220.87
Correct answer: NEC 220.82
NEC 220.82 provides an optional simplified load calculation method for one-family dwellings as an alternative to the standard method.
Question 2: Per NEC Table 220.54, what is the demand factor for household electric dryers when 5 dryers are supplied from the same feeder?
- 100%
- 80% (Correct answer)
- 70%
- 50%
Correct answer: 80%
NEC Table 220.54 specifies an 80% demand factor when calculating feeder load for 5 household electric dryers.
Question 3: For a 200-ampere residential service, what is the minimum copper conductor size per NEC Table 310.12?
- 2/0 AWG
- 3/0 AWG (Correct answer)
- 4/0 AWG
- 250 kcmil
Correct answer: 3/0 AWG
NEC Table 310.12 specifies 3/0 AWG copper as the minimum conductor size for a 200-ampere service entrance in a dwelling unit.
Question 4: Per NEC 230.71, what is the maximum number of service disconnecting means permitted for a single service?
- Two
- Four
- Six (Correct answer)
- Eight
Correct answer: Six
NEC 230.71(A) limits the service disconnecting means to no more than six switches or circuit breakers grouped in one location.
Question 5: How is the size of a neutral service entrance conductor determined per NEC 220.61?
- Always equal to the ungrounded conductors
- Based on the maximum unbalanced load between neutral and any one ungrounded conductor (Correct answer)
- Always at least 4 AWG copper regardless of load
- Equal to 125% of the total connected load
Correct answer: Based on the maximum unbalanced load between neutral and any one ungrounded conductor
NEC 220.61 requires the neutral conductor to be sized based on the maximum unbalanced load, which is the load between the neutral and any one ungrounded conductor.
Question 6: What minimum clearance must service drop conductors maintain above a residential rooftop with a slope of at least 4-in-12 per NEC 230.24?
- 3 feet (Correct answer)
- 6 feet
- 8 feet
- 10 feet
Correct answer: 3 feet
Per NEC 230.24(A) Exception 2, service conductors above a roof with a slope of not less than 4 inches per foot require only a 3-foot clearance.
PC Load Calculations and Service Entrance 2
The optional calculation method for a one-family dwelling load is located in which NEC section?