Can neutrals and grounds share a bar at the service disconnect?

Yes. Section 250.24(B) and 250.142(A) require the grounded conductor to be bonded to the service disconnect enclosure, so the equipment grounding conductors and neutrals share the bonded bar at that one location.

Can I bond neutrals and grounds together in a subpanel?

No. Section 250.142(B) prohibits using the grounded conductor for equipment grounding on the load side of the service disconnect, so a subpanel needs an isolated neutral bar and a separate equipment ground bar.

Do I need to remove paint before landing a ground on an enclosure?

Yes. Section 250.12 requires nonconductive coatings such as paint and enamel to be removed from threads and contact surfaces, or you must use fittings designed to make removal unnecessary.

Can the equipment grounding conductor land on the enclosure at the service disconnect?

Yes. At the service disconnecting means, the grounded conductor, the equipment grounding conductors, the enclosure, and the grounding electrode conductor all come together at one point. Section 250.24(A)(1) requires the grounded service conductor to be connected to the grounding electrode system at any accessible point from the load end of the overhead service conductors or service lateral up to and including the terminal of the service disconnecting means. Section 250.24(B) requires a main bonding jumper, installed per 250.28, connecting the grounded conductor to the service disconnect enclosure. So landing the equipment grounding conductor on the can or on the ground bar bonded to the can is exactly what the code intends at that location.

Why the service is different from every other panel

Section 250.142(A) permits the grounded circuit conductor to be used for grounding non-current-carrying metal parts of equipment on the supply side of the service disconnecting means. Section 250.142(B) then prohibits that same practice on the load side of the service disconnecting means, with limited exceptions. That single pair of subsections is the reason neutrals and grounds bond at the service and separate everywhere downstream.

Section 408.40 reinforces it for panelboards: equipment grounding conductors shall not be connected to the terminal bar for grounded conductors unless the bar is identified for the purpose and located where the interconnection is permitted, which is the service equipment. In a subpanel, remove or leave out the bonding screw, install a separate equipment ground bar, and keep the neutrals isolated.

Details that fail inspection at the service

Section 250.12 requires nonconductive coatings such as paint, lacquer, and enamel on equipment to be removed from threads and contact surfaces, or the connection must be made by fittings designed to make removal unnecessary. Scrape the paint or use a listed self-grounding fitting or a bonding bushing with a star washer.

Section 250.92(B) covers bonding at service raceways, and the acceptable methods are the grounded service conductor connection, threaded couplings and hubs made up wrenchtight, threadless couplings and connectors made up tight, bonding jumpers, or other listed devices. Standard locknuts and bushings alone do not bond a service raceway. Section 250.97 imposes a similar requirement on circuits over 250 volts to ground.

Section 250.24(C) sets the minimum size for the grounded conductor run to the service disconnect, and it cannot be smaller than the value in Table 250.102(C)(1) based on the size of the ungrounded service conductors, even if the calculated neutral load is small. This one trips people on 400 and 600 ampere services where the load is nearly balanced.

Field takeaway

At the service disconnect, ground and neutral bond and the EGC lands on the enclosure or a bonded bar. One bonding point, one main bonding jumper, everything downstream separated. Scrape the paint, use bonding hardware on the service raceways, and size the grounded conductor from Table 250.102(C)(1) as a floor.