Tenant build-out lighting panel
What's wrong here?
- Three single-pole breakers on a shared-neutral circuit have no handle tie
- Each 120 V circuit in a cable must have its own neutral conductor
- A multiwire branch circuit must use a 3-pole common-trip breaker
- Red and blue insulation is not permitted for ungrounded conductors
Show the answer and the code reference
The answer
The multiwire branch circuit in the right-hand MC cable is landed on three separate single-pole breakers with no handle tie, so its ungrounded conductors cannot be disconnected together.
Correct choice: 1. Three single-pole breakers on a shared-neutral circuit have no handle tie
A multiwire branch circuit shares one neutral among two or three ungrounded conductors on different phases. 210.4(B) requires a means that simultaneously disconnects all of its ungrounded conductors where the circuit originates, normally a multipole breaker or single-pole breakers joined by an identified handle tie (240.15(B)(1)). Without it, someone shuts off one breaker to work on a fixture while the shared neutral is still carrying return current from the other two circuits; open that neutral and the electrician ends up in series with the loads that are still energized. Compare the cable at upper left: the same kind of circuit, done right with a handle tie.
How to fix it
Install the panel manufacturer's identified handle tie across the three breakers fed by the right-hand cable, or replace them with a 3-pole breaker. Confirm the three conductors are on three different phases and keep the circuit's conductors grouped in the panel per 210.4(D) and 200.4(B).
Code references
NEC 2023 210.4(B) — Disconnecting Means
Each multiwire branch circuit must be provided with a means that simultaneously disconnects all ungrounded conductors at the point where the branch circuit originates.
Drills citing 210.4(B)NEC 2023 240.15(B)(1) — Multiwire Branch Circuits
Individual single-pole circuit breakers, with identified handle ties, are permitted as the protection for each ungrounded conductor of multiwire branch circuits that serve only single-phase line-to-neutral loads.
Drills citing 240.15(B)(1)NEC 2023 210.4(D) — Grouping
The ungrounded and grounded conductors of each multiwire branch circuit must be grouped in accordance with 200.4(B): identified or grouped by wire markers, cable ties, or similar means in at least one location within the enclosure, except where they enter in a cable or raceway unique to the circuit that makes the grouping obvious.
Drills citing 210.4(D)
2026 NEC:not yet checked Confidence: low
Minnesota
Minnesota adopts the NEC by reference without amendment (Minn. Rules 1315.0200; Minn. Stat. 326B.35), so 210.4(B) applies as published. The 2023 NEC governs permits filed July 1, 2023 through Aug. 16, 2026; the 2026 NEC governs permits filed on or after Aug. 17, 2026 (exams moved to the 2026 NEC on Sept. 8, 2026). See the 2026 NEC note on this drill.
How Minnesota adopts the NECWhy the other choices are wrong
- Each 120 V circuit in a cable must have its own neutral conductor. A shared neutral is exactly what a multiwire branch circuit is, and 210.4(A) permits it. The ungrounded conductors just have to be on different phases and be disconnected together.
- A multiwire branch circuit must use a 3-pole common-trip breaker. A multipole common-trip breaker is one way to comply, not the only one. For line-to-neutral loads, 240.15(B)(1) permits single-pole breakers with identified handle ties, and the tie satisfies the simultaneous-disconnect rule in 210.4(B), as the cable at upper left shows.
- Red and blue insulation is not permitted for ungrounded conductors. White and gray are reserved for grounded conductors (200.7) and green, green with yellow stripes, or bare for equipment grounding conductors (250.119). Black, red and blue is the usual 208Y/120 V phase coding; 210.5(C)(1) requires a documented or posted identification scheme only where branch circuits are supplied from more than one nominal voltage system.