Quick Hits

EPISODE 6 — Conductors in Parallel (310.10(G))

Slide 1 — Hook "One of the most detailed subsections in the whole article — the rules for splitting a big circuit across multiple smaller conductors run in parallel."

Slide 2 — The basics

• Parallel conductors (electrically joined at both ends) are only allowed in sizes 1/0 AWG and LARGER — with narrow exceptions for smaller conductors feeding control power to instruments/contactors/relays/solenoids (if in the same raceway/cable, each conductor sized for the full shared load, and OCP that won't overload the rest if one disconnects) or high-frequency (360Hz+) applications, plus an engineering-supervised exception letting 2 AWG/1 AWG neutral conductors run in parallel on EXISTING installations to fight harmonic overheating.

Slide 3 — Matching characteristics & other requirements

• Every conductor making up a parallel set (ungrounded, grounded, neutral, EGC, bonding jumpers) must match: same length, same material, same circular mil size, same insulation type, same termination method.

• Where run in SEPARATE cables/raceways: each raceway/cable needs the same number of conductors and the same electrical characteristics — though different parallel SETS don't have to match each other's physical characteristics.

• Ampacity correction/adjustment follows 310.15(B)/(C); parallel EGCs follow 250.122 sizing (smaller sectioned EGCs are okay in multiconductor cables if the combined area meets 250.122); parallel bonding jumpers follow 250.102 sizing.

Slide 4 — Quiz + CTA Q: "Under the general rule, what's the smallest conductor size permitted to be run in parallel?" A) 4 AWG B) 2 AWG C) 1/0 AWG D) 250 kcmil

✅ Answer: C — 310.10(G)(1): 1/0 AWG and larger, under the general rule (narrow exceptions exist below that).

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