Load Calculations and Service Entrance Flashcards

The optional calculation method for a one-family dwelling load is located in which NEC section?

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.

Per NEC Table 220.54, what is the demand factor for household electric dryers when 5 dryers are supplied from the same feeder?

Answer: 80%

NEC Table 220.54 specifies an 80% demand factor when calculating feeder load for 5 household electric dryers.

For a 200-ampere residential service, what is the minimum copper conductor size per NEC Table 310.12?

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.

Per NEC 230.71, what is the maximum number of service disconnecting means permitted for a single service?

Answer: Six

NEC 230.71(A) limits the service disconnecting means to no more than six switches or circuit breakers grouped in one location.

How is the size of a neutral service entrance conductor determined per NEC 220.61?

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.

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?

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.