Chapter 3 of 624% of exam
Branch Circuits & Wiring Methods
Branch circuits are the final wiring that carries power to receptacles, lighting, and equipment. This chapter covers branch-circuit rules, GFCI and AFCI protection, receptacle placement, wiring methods and raceways, box fill, derating, voltage drop, and required working space.
Branch Circuits (Article 210)
A branch circuit is the conductors between the final overcurrent device and the outlets it serves. Article 210 sets the ratings, the loads permitted on general-purpose and individual circuits, and the requirement that continuous loads be counted at 125%. Multi-outlet circuits in dwellings are generally limited to 15- and 20-ampere ratings.
Continuous load
The branch-circuit rating must be at least 125% of the continuous load plus 100% of the noncontinuous load.
2023 NEC §210.19Receptacle circuit loading
On a 20-amp general-purpose circuit, receptacle outlets are counted at 180 VA each for load calculation in non-dwelling occupancies.
2023 NEC §220.14(I)Small-appliance circuits
At least two 20-amp small-appliance branch circuits must serve the kitchen and dining receptacles in a dwelling.
2023 NEC §210.11(C)Bathroom circuit
At least one 20-amp branch circuit must supply bathroom receptacle outlets and serve no other areas.
2023 NEC §210.11(C)(3)GFCI, AFCI & Receptacle Placement
Ground-fault circuit interrupters protect people from shock by opening on small leakage currents, while arc-fault circuit interrupters detect dangerous arcing to prevent fires. Article 210 also dictates where receptacles must be placed in dwellings so no point along a wall is far from an outlet.
GFCI protection
GFCI protection is required for receptacles in bathrooms, kitchens, garages, outdoors, and other damp or wet locations.
2023 NEC §210.8AFCI protection
AFCI protection is required for most 120-volt, 15- and 20-amp branch circuits supplying dwelling living areas and bedrooms.
2023 NEC §210.12Wall receptacle spacing
Receptacles must be placed so no point along the floor line of a wall is more than 6 feet from a receptacle.
2023 NEC §210.52(A)Countertop receptacles
Kitchen countertops require receptacles so that no point is more than 24 inches from one, with island and peninsula rules applying.
2023 NEC §210.52(C)Wiring Methods & Raceways (Articles 300, 342, 344, 352, 358)
Wiring methods must protect conductors from physical damage and the environment. Article 300 gives general installation rules such as burial depth and securing, while individual articles cover EMT, RMC, PVC, and flexible conduits. Each method has support intervals and permitted uses based on exposure and location.
EMT support
Electrical metallic tubing must be securely fastened within 3 feet of each box and at intervals not exceeding 10 feet.
2023 NEC §358.30PVC conduit expansion
Rigid PVC conduit requires expansion fittings where thermal movement is expected, and support intervals vary by trade size.
2023 NEC §352.30Underground burial depth
Minimum cover for underground installations is set by Table 300.5 based on wiring method and circuit voltage.
2023 NEC §300.5Liquidtight flexible conduit
LFMC is permitted where flexibility or protection from liquids is needed, within the size and length limits of its article.
2023 NEC §350.30Cables, Box Fill & Conduit Fill (314.16, Chapter 9)
Cable assemblies like NM and MC bundle conductors for quick installation, each with rules on support and permitted locations. Boxes must be large enough for the conductors, devices, and fittings inside them, and raceways are limited in how many conductors they may contain to allow heat dissipation and pulling.
NM cable use
Nonmetallic-sheathed cable is permitted in many dwellings but is restricted in wet locations and where subject to physical damage.
2023 NEC §334.12Box fill calculation
The volume required in a box is the sum of conductor, device, and fitting allowances computed from Table 314.16(B).
2023 NEC §314.16Conduit fill limit
For more than two conductors, a raceway may be filled to no more than 40% of its cross-sectional area.
2023 NEC Chapter 9, Table 1MC cable support
Metal-clad cable must be secured within 12 inches of a box and at intervals not exceeding 6 feet.
2023 NEC §330.30Derating, Voltage Drop & Working Space (110.26)
When many conductors share a raceway or ambient heat is high, ampacity must be derated so conductors do not overheat. Voltage drop, though generally a recommendation rather than a rule, affects performance over long runs. Working space around equipment is a firm safety requirement.
Conductor derating
Ampacity adjustment and temperature correction are multiplied together when both apply to a set of conductors.
2023 NEC §310.15Voltage drop guidance
The code recommends limiting branch-circuit voltage drop to 3%, and combined feeder and branch drop to 5%, for reasonable efficiency.
2023 NEC §210.19 Informational NoteWorking space depth
A minimum clear working depth in front of live equipment ranges from 3 to 4 feet or more depending on voltage and conditions.
2023 NEC §110.26(A)Working space width and height
The working space must be at least 30 inches wide and provide headroom of 6.5 feet in front of electrical equipment.
2023 NEC §110.26(A)(2)Test your knowledge
Practice questions on Branch Circuits & Wiring Methods