Garage subpanel, cover off
What's wrong here?
- Grounds share the neutral bars, and the neutral is bonded to the can at a subpanel
- This panel needs its own ground rod because it is supplied by a feeder, not the service
- A subpanel must have a main breaker; main-lug-only panels are not allowed here
- Nothing. This installation is compliant
Show the answer and the code reference
The answer
At this feeder-supplied subpanel the neutral is bonded to the enclosure with the green bonding screw and the equipment grounding conductors, including the feeder EGC, are landed on the neutral bars.
Correct choice: 1. Grounds share the neutral bars, and the neutral is bonded to the can at a subpanel
The neutral and equipment grounding conductors are joined only at the service (the main bonding jumper, 250.24(B) and 250.28). On the load side of the service disconnecting means, 250.24(A)(5) and 250.142(B) prohibit connecting the grounded conductor to equipment grounding conductors or to equipment enclosures. With the bonding screw in and the grounds on the neutral bar, normal neutral current divides between the white feeder conductor, the green feeder EGC, the EMT and the enclosure, so metal that should carry no current does, and a lost neutral can energize every grounded surface on the circuit. 408.40 requires a separate EGC terminal bar bonded to the cabinet, and bars meant for neutrals may not carry EGCs at a location like this.
How to fix it
Remove the green bonding screw (or strap) so the neutral bars float. Then install the manufacturer's ground bar kit bonded to the can and move every bare and green conductor, including the feeder EGC, onto it, so only white conductors stay on the neutral bars.
Code references
NEC 2023 250.24(A)(5) — Load-Side Grounding Connections
A grounded conductor shall not be connected to normally non-current-carrying metal parts of equipment, to equipment grounding conductors, or be reconnected to ground on the load side of the service disconnecting means, except as otherwise permitted in Article 250.
Drills citing 250.24(A)(5)NEC 2023 250.142(B) — Load-Side Equipment
Except as permitted in 250.30(A)(1) and 250.32(B)(1) Exception No. 1, a grounded circuit conductor shall not be used for grounding non-current-carrying metal parts of equipment on the load side of the service disconnecting means.
Drills citing 250.142(B)NEC 2023 408.40 — Equipment Grounding Conductor
Where separate equipment grounding conductors are provided, a terminal bar for them shall be secured inside the cabinet and bonded to it; an EGC shall not be connected to a terminal bar provided for grounded conductors unless the bar is identified for the purpose and is located where interconnection of EGCs and grounded conductors is permitted or required by Article 250.
Drills citing 408.40
2026 NEC:not yet checked Confidence: low
Minnesota
Minnesota adopts the NEC as published, with no section-by-section amendments (Minn. Stat. 326B.35; Minn. Rules 1315.0200), so 250.24, 250.142 and 408.40 read the same as in the 2023 NEC. The 2023 NEC governs permits filed from July 1, 2023 until the 2026 NEC took effect; for newer permits, check the section numbers in the 2026 edition. Expect a bonded neutral at any subpanel to be written up at rough-in or final.
How Minnesota adopts the NECWhy the other choices are wrong
- This panel needs its own ground rod because it is supplied by a feeder, not the service. Grounding electrodes at a feeder-supplied panel are required only for a separate building or structure (250.32(A)); a panel in the same building is grounded through the feeder EGC.
- A subpanel must have a main breaker; main-lug-only panels are not allowed here. A main-lug-only panelboard is fine when the feeder breaker in the main panel protects it (408.36); a building disconnect is a separate-building rule (225.31).
- Nothing. This installation is compliant. Neutral-to-ground bonding belongs only at the service; on the load side the neutral bar must be isolated and the EGCs kept on their own bar.