Spot the Violation

ElectricalPanels, breakers & overcurrentLevel 32023 NEC

Basement subpanel at rough-in

Basement mechanical room. A 24-space subpanel with its dead front removed is surface-mounted on the wall just to the right of a gas furnace; the wall to the right of the panel is open. A black-sheathed 6/3 NM cable enters the top left through its own connector; its black and red 6 AWG conductors land on the load terminals of a 2-pole 50 A breaker in the top two spaces of the left column, and a small steel bracket screwed to the panel interior sits over the end of that breaker. The 6 AWG white lands on the main lug of a neutral bar mounted on insulating standoffs, with a second neutral bar strapped to it on the right, and the bare conductor runs to a separate ground bar screwed directly to the back of the enclosure. Seven yellow and white NM branch cables enter through individual connectors and land on single-pole breakers with test buttons, the yellow cables on 20 A breakers and the white cables on 15 A breakers, with whites on the neutral bars and bare copper on the ground bar. The lower spaces are empty. 6/3 NM-B 5020152020151520
Basement mechanical room, new subpanel, dead front off for inspection

What's wrong here?

  1. Nothing. This installation is compliant
  2. A plug-in breaker may not be back-fed to serve as a panel's main
  3. The neutral bar must be bonded to the enclosure with the green bonding screw
  4. The back-fed breaker's handle must move up for ON
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Show the answer and the code reference

The answer

Nothing is wrong: the back-fed 50 A main breaker is held in place by a hold-down kit, the neutrals are isolated from the enclosure, the grounds land on a separate bonded ground bar, and each branch cable is on a breaker sized for it.

Correct choice: 1. Nothing. This installation is compliant

A plug-in breaker that terminates the feeder is energized on what are normally its load terminals, so if it were pulled off the bus while switched on, its stabs would be live; 408.36(D) requires an additional fastener for it, and the screwed bracket over the 2-pole breaker is that fastener. The feeder and branch neutrals land on bars mounted on insulating standoffs and the grounds land on a separate bar screwed to the can, which is how a feeder-supplied panel has to be set up (250.24(A)(5)). The 6 AWG copper NM is good for 55 A at 60 C (334.80, Table 310.16), enough for the 50 A main and for a supply breaker up to 60 A under 240.4(B), and every white (14 AWG) cable is on a 15 A breaker and every yellow (12 AWG) cable on a 20 A. The furnace close beside the panel is not a problem either: the 30 in working width does not have to be centered on the panel, and the wall to the right is clear.

How to fix it

No correction needed. Leave the hold-down kit in place any time the breaker is reinstalled, and keep the green bonding screw out of the neutral bar in any panel fed from a feeder.

Code references

  • NEC 2023 408.36(D) — Back-Fed Devices

    Plug-in overcurrent devices or plug-in main lug assemblies that are back-fed and terminate field-installed ungrounded supply conductors must be secured in place by an additional fastener that requires other than a pull to release the device from the panel.

    Drills citing 408.36(D)

  • NEC 2023 250.24(A)(5) — Load-Side Grounding Connections

    A grounded (neutral) conductor may not be connected to normally non-current-carrying metal parts of equipment or to equipment grounding conductors, or be regrounded, on the load side of the service disconnecting means except where Article 250 permits.

    Drills citing 250.24(A)(5)

  • NEC 2023 240.81 — Indicating

    Circuit breakers must clearly indicate open or closed position, and where breaker handles operate vertically rather than rotationally or horizontally, the up position must be on.

    Drills citing 240.81

  • NEC 2023 110.26(A)(2) — Width of Working Space

    The width of the working space in front of the equipment must be the width of the equipment or 30 in, whichever is greater, and in all cases must permit equipment doors or hinged panels to open at least 90 degrees.

    Drills citing 110.26(A)(2)

2026 NEC:same rule and number. No 2026 change to the back-fed device hold-down rule in 408.36(D) turned up in code-change summaries, so it appears unchanged; the supporting 250.24(A)(5) citation may have moved in the reorganized 2026 Article 250 and was not checked. Confidence: low

Minnesota

MN adopts the NEC rule as writtenConfidence: high

Minnesota adopts the NEC by reference without amendment (Minn. Rules 1315.0200; Minn. Stat. 326B.35), so 408.36(D) 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 NEC

Why the other choices are wrong

  • A plug-in breaker may not be back-fed to serve as a panel's main. Back-feeding is permitted; the exception is a breaker marked Line and Load, whose listing does not allow it. 408.36(D) recognizes back-fed plug-in breakers as long as they are secured by an additional fastener, which the hold-down bracket provides.
  • The neutral bar must be bonded to the enclosure with the green bonding screw. This panel is fed by a feeder, so the neutral must stay isolated from the enclosure and the equipment grounding conductors. The neutral-to-ground bond belongs at the service (or a separately derived system), not in a feeder-supplied panel (250.24(A)(5), 250.142(B)).
  • The back-fed breaker's handle must move up for ON. 240.81 applies only to breaker handles that operate vertically. These breakers operate side to side, so the rule does not apply to them.
Safety hazardLevel 3 · Master#panel#subpanel#back-fed breaker#hold-down#feeder#neutral isolation#calibration

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