National Electrical Code (NFPA 70) and code changes
What this domain tests
This domain tests how well you locate and apply NFPA 70 to field installations, using the edition and New Hampshire amendments named in the candidate bulletin. Expect calculation items, wiring-method and grounding questions, and code-change items that separate the current edition from older editions.
Core rules
- Begin with Article 90 and the definitions in Article 100. Then go to the article that owns the subject: 210 branch circuits, 220 calculations, 230 services, 240 overcurrent, 250 grounding and bonding, 300 wiring methods, 310 conductors, 314 boxes, and 430 motors.
- Code changes are conditional, not trivia. For example, 210.8 has expanded GFCI protection by location and voltage; 230.85 requires a marked emergency disconnect for one- and two-family dwellings; 230.67 requires service SPDs for dwelling units. Read the adopted edition’s exceptions instead of reciting an older list.
Worked example
A 4 in. x 4 in. x 1-1/2 in. metal box contains six 12 AWG current-carrying conductors, one 12 AWG equipment grounding conductor, one cable clamp, and one duplex receptacle. Box volume is 4 x 4 x 1.5 = 24 cu in. Under 314.16(B), count six conductors + one EGC (all EGCs count as one) + one clamp + two for the device = 10 conductor equivalents. At 2.25 cu in. per 12 AWG, fill is 10 x 2.25 = 22.5 cu in., so the box is compliant with 1.5 cu in. to spare.
Traps
Counting each EGC separately, omitting the clamp or device, using the 90°C ampacity column without checking termination ratings, and applying a memorized GFCI list from the wrong edition.