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Code Q&A: Determining the Minimum Number of Circuits Required

Dec. 22, 2016
NEC guidelines for the minimum number of general lighting and general-use receptacle branch circuits

Q. How do you determine the minimum number of general lighting and general-use branch circuits required by the NEC for dwellings?

Find the Answer

A. The minimum number of general lighting and general-use receptacle branch circuits must be determined by dividing the total calculated load in amperes by the ampere rating of the circuits used [210.11(A)].

For example, let’s say you’re trying to determine how many 15A, 120V circuits are required for the general lighting and general-use receptacles for a dwelling having floor area of 1,500 sq ft, exclusive of an unfinished cellar not adaptable for future use [Example D1(a) in Annex D]?

Step 1: Determine the total VA load.

VA = 1,500 sq ft x 3VA per sq ft [Table 220.12]
VA = 4,500VA

Step 2: Now solve for the amperes.

I = VA ÷ E
I = 4,500VA ÷ 120V
I = 38A

Step 3: Determine the number of circuits.

Number of Circuits = 38A ÷ 15A
Number of Circuits = Three 15A or two 20A

Note: There’s no limit to the number of receptacles on a circuit in a dwelling unit.

If you calculate the load based on the volt-amperes/square foot method, the wiring system must be provided to serve the calculated load, with the loads evenly proportioned among multioutlet branch circuits within the panelboard.

These materials are provided to us by Mike Holt Enterprises in Leesburg, Fla. To view Code training materials offered by this company, visit www.mikeholt.com/code

About the Author

Mike Holt

Mike Holt is the owner of Mike Holt Enterprises (www.MikeHolt.com), one of the largest electrical publishers in the United States. He earned a master's degree in the Business Administration Program (MBA) from the University of Miami. He earned his reputation as a National Electrical Code (NEC) expert by working his way up through the electrical trade. Formally a construction editor for two different trade publications, Mike started his career as an apprentice electrician and eventually became a master electrician, an electrical inspector, a contractor, and an educator. Mike has taught more than 1,000 classes on 30 different electrical-related subjects — ranging from alarm installations to exam preparation and voltage drop calculations. He continues to produce seminars, videos, books, and online training for the trade as well as contribute monthly Code content to EC&M magazine.

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