Wiring and Protection
What to master
This is the largest slice of the Code: Article 210 branch circuits, 215 feeders, 220 calculations, 230 services, 240 overcurrent protection, 250 grounding and bonding, and 280/285 surge protection. Memorize 240.4(D) small-conductor limits (14 AWG = 15 A, 12 AWG = 20 A, 10 AWG = 30 A), the grounding electrode conductor sizing table in 250.66, and the equipment grounding conductor table in 250.122. Know 210.52 receptacle placement, the 210.8 GFCI list (bathrooms, kitchens, garages, outdoors, unfinished basements, within 6 ft of a sink), and the 210.12 AFCI scope, which the 2023 edition expanded to kitchens and laundry areas.
Traps
Confusing grounding (earth reference) with bonding (fault-current path); omitting the bonding jumper around a water meter; assuming GFCI replaces the need for a grounded conductor; measuring receptacle spacing in straight-line distance rather than along the floor line; and forgetting that door openings count as part of the wall line.
Worked example
210.52(A) requires that no point along the floor line be more than 6 ft from a receptacle, which means a 12 ft maximum spacing. A 24 ft living-room wall therefore needs at least two receptacles, placed no more than 6 ft from each end and no more than 12 ft apart.