Did this install today on my home. How'd I do?

I asked an old electrician and he said that I ought not to mix the Neutral with the Ground at the main like that cause "it could cause problems", though he did not give further detail. But if the Neutral and Ground Bus are bonded in the main anyway (which they definitely are on this panel), what does that matter? I used the ground bus for the #6AWG Neutral (white wire) because the other buses did not have any opening's big enough for the #6, at least it didn't look like it would fit...

I used #6AWG THHN for all 3 conductors and #10AWG THHN green for the ground, and these are are conveyed in the Steel Flex 3/4" you can see coming in from underneath. I installed bushings in the FMC where they connect to the compression fittings. The Sub panel Neutral is Isolated. This is fed from a 50 Amp (Connecticut Electric UBITBA250 Challenger “A” Series Circuit Breaker, 2-Pole 50-Amp) housed in the main. Which used to house a 30 amp for an old electric dryer circuit no longer in use. I had to source breakers for this old Challenger panel and they were pricey.

It's mounted to a 3/4" plywood board that is then fastened to the studs. The main is a 100 AMP service and according to the usage calculations for the house I'm well within that. Most big appliances are gas. I needed more outlets in the garage for my dust collector and table saw.

I live in San Francisco. The Panels are located in the garage at street level. Plan is to run 1/2" emt to job boxes along the workbench top, protected with GFCI outlets. I may at a later time install a 220 for the dust collector and a welder, which is why I went 50 amp.

So am I gonna burn the place down?

Sub Panel and Main

Ground and Neutral

  • Holy smokes, what's with the tiny subpanel? It's obvious you're putting the subpanel in because you're out of room in the main panel, but you're just doing it to yourself again, you'll run out of space again! Those twin breakers in the main panel are not normal, those are "cheaters" to let you overstuff a panel, which is bad. Get rid of that piece-o-junk and get at least a 42 space if not a 60, with an eye toward making that the main panel at some future point. Jun 7 '17 at 15:23
  • I only need a few extra spaces for tools. I'm a renter. Additionally the main panel has no shut off, I'd have to pull the meter socket and PGE would be notified if I did (smart meter). Also, homeowner is a bit cheap, doesn't want to spend the money for new parts (an entirely new panel and all the breakers would be costly). I'm not exceeding the 100 Amps the panel delivers, and slim breakers are perfectly acceptable.
    – Wilkoe
    Jun 7 '17 at 15:34
  • RENTER! That explains much. (in SF this sort of thing is normal, pretty mild actually, due to the insanely distorted market.) And yes that does change the economics somewhat. It's a shame, since you were that deep into it, and had the main power isolated, I'd have slapped a new Siemens main panel in there with a main breaker (to get rid of that Challenger, which might burn your house down.) And earn the eternal gratitude of the landlord! Jun 7 '17 at 15:38
  • Tearing up some sheetrock, running flex, and wiring up the sub was a quick job. :) , Oh and I've heard about the challenger panels, I am looking into this one to see if it's one of the "bad ones", something to do with the bus material on certain models...
    – Wilkoe
    Jun 7 '17 at 15:43

OK the NEC and AHJ have always allowed the grounding conductors (Ground) and the grounded conductor (Neutral) to be connected to the neutral bus bar in the main panelboard or loadcenter. You are correct the busses are interlocked and bonded. The only reason some electricians put the ground on one side and the neutral on the other is because of the "workmanlike manner" clause. I have never seen where mixing them has ever caused any problems.

Now, your sub panel is not covered under this rule due to the single point of ground rule. You need to install a grounding bus and an isolated neutral bus. Each bus must be connected from the service panel with a corresponding conductor and you do not bond the sub panel neutral. This is true with any other device, equipment or sub panel installed downstream of the service panel.

  • 1
    The Sub panel does have a ground bus which I added, and the Neutral bus is isolated in the sub as well. It's hard to tell from the pictures. In the top left of the photo the #10 green goes to the ground bus, which is connected to the panel, and the big white #6 is connected to the Neutral bus which is isolated (unless you add a screw supplied with the panel to bond it).
    – Wilkoe
    Jun 7 '17 at 19:04

That doesn't look like a main panel and a subpanel. It looks like a subpanel and another subpanel. In that case, the neutrals and ground would remain SEPARATE in both, like it is already set up.

"But if the Neutral and Ground Bus are bonded in the main anyway, what does that matter?"

They both MUST go to the same point at the MAIN. In ALL downstream subpanels they must be separated. If you don't do that, you are sending current back on the equipment (green or bare copper) ground which can result in someone getting shocked or electrocuted.

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