Quick Hits

Episode 4 — Tap Conductors, Transformer Secondaries, and Dwelling Conductors

Covers: 240.4(E)–(H)

Hook: Some conductors get their overcurrent protection from somewhere else entirely — here's where the code sends you.

Slide 2: Tap conductors get their protection rules from other sections entirely (210.19/210.20 for range/cooking taps, 240.5(B)(2) for fixture wire, 240.21 for location rules, 368.17 for busway taps, 430.53(D) for single-motor taps) — not from 240.4 directly. Transformer secondary conductors generally aren't considered protected by the primary-side OCPD, except for a single-phase 2-wire secondary or a delta-delta 3-wire secondary, where primary protection can cover the secondary if it doesn't exceed the secondary ampacity times the voltage ratio.

Slide 3: A whole table of specific applications (motors, welders, fire alarm circuits, capacitors, phase converters, and more) point to their own dedicated articles for overcurrent rules instead of the general 240.4 rule. And dwelling unit services/feeders get a special allowance — sizing overcurrent protection using the increased values in 310.12, which accounts for the load diversity typical of residential services.

Quiz: Which conductor type gets a special dwelling-specific overcurrent sizing allowance under 240.4(H)?
Answer: One- and two-family dwelling service and feeder conductors, sized per 310.12.

CTA: Follow — flexible cords and fixture wire protection is next.

← View Chapter 2 Home

← Back To Article 240 Home

← Back To Quick Hits Home