Branch Circuits, Wiring Methods, and Grounding
This domain covers the branch-circuit and wiring-method rules that most often appear in residential inspections. The IRC addresses branch-circuit requirements in Chapter 37 and wiring methods in Chapter 38. You need to connect circuit rating, protection, support, and grounding into one coherent installation.
Core rules
- Branch circuits must be rated for the load and protected at their ampacity. Kitchen small-appliance circuits must be 20 A, and at least two are required for countertop receptacles.
- GFCI protection is required in locations such as bathrooms, garages, outdoors, crawl spaces, unfinished basements, kitchen countertops, and at sinks. The location triggers protection; the equipment type does not excuse it.
- AFCI protection is required for dwelling-unit branch circuits supplying outlets in specified rooms such as bedrooms, living rooms, dining rooms, and similar areas, as adopted by the IRC.
- Nonmetallic-sheathed cable must be supported within 12 inches of boxes and at intervals not exceeding 4 1/2 feet. Protect cable from nails and physical damage with listed plates where required.
- Equipment grounding conductors must be installed with feeder and branch circuits. Receptacles must be grounding type, and the neutral must never serve as an equipment ground on the load side of the service.
Worked example
A 20 A branch circuit supplies a receptacle in an unfinished basement for a freezer. Does it require GFCI protection? Yes. An unfinished basement is a listed GFCI location, and a dedicated freezer receptacle is not a general exception. The circuit rating, the appliance, and the basement use do not remove the requirement. Install GFCI protection and keep the equipment grounding conductor continuous.
Traps
- Assuming GFCI is only for bathrooms.
- Using NM cable in wet or damp locations where it is not permitted.
- Omitting AFCI because the room is not a bedroom.
- Supporting cable by memory rather than the 12-inch and 4 1/2-foot rules.