I have a simple question, that I believe I already know the answer to, but just need confirmation before moving on. I had an electrician install a 100 amp subpanel installed on a newly built detached garage. He used 4 wire (2 hot, 1 neut, 1 gnd) off the main, unbonded the neutral and ground in the subpanel, and also attached the grounding bar to an additional grounding rod located at the detached garage. I believe everything was done correctly, except for grounding the subpanel to the grounding bar. The grounding bar is floating, and not making contact with the panel. Shouldn't the grounding bar be bonded to the subpanel?
Short answer, I agree, he overlooked it. Long answer:
Maybe. This was done with individual wires (THHN, XHHW etc) Those require conduit, and it looks like metal conduit. Metal conduit is a valid grounding path, in which case he didn't even need the ground wire.
That said, I'm not comfortable with metal conduit as a grounding path outdoors because it rusts out, and leakage current hastens that. So I am happy that he wired ground.
Further, neutral is not ground. Grounds should be webbed, and there's good reason to bond ground to ground whenever feasible. It's never wrong to double up a ground connection, so removing the ground bar-chassis bond was a useless thing to do. I'm not sure why he did it.
I would put the strap back in.
Both bars are insulated from the frame, so I think the manufacturer designed this panel with the flexibility to use 1 or both bars as neutral. They also sell accessory ground bars which are not insulated from frame.
Overall, the panel looks like excellent work done above-and-beyond the call. The only quibbles I have are
- Runt wires. All the leads have been cut short to make the panel neater. Despite what 110.12 says, the job of those wires is not to look pretty, it's to let hot and neutral reach any space in the panel. So you are free to move things around as needed.
- Lack of AFCI/GFCI. This being new construction, I'm fairly sure NEC 2011/14 apply, and you need AFCI and/or GFCI here. Remember when I said "hot AND neutral wires need to be able to reach the breaker?" That's why. The neatness is undone if the panel becomes a maze of extension wires and wire nuts.
- The outbuilding requires a main shutoff switch, and he is using a 2-pole breaker that is backfed. The important stuff is done: it is bolted down; however I thought "upper left corner" was a standard location. I could be wrong. The wires have been runted too short for that to be possible.
But again, to really bang this home, the work I see here is superlative. A lot of optional stuff was done that isn't even nearly required by Code, like marking where the cables go. Of the various panels I see posted here, this is a high water mark.