First sub panel install. Anything I can improve on before calling for my rough-in inspection?

Only thing I’m not sure of (and aware of) is that I’m using the panel as the ground between the second and first grounding bus, not sure if I should link the buses directly with some bare #6. I’m guessing not as the metal box is probably a bigger grounding plane than copper wire.

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    A bit late now, but since you have the space (not everyone does) you could have put in a much bigger panel, for very little additional cost, and had room for expansion. You've got only two spaces available for future use. Jun 9 at 15:08
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    Probably correct that you don't need it, but I'd put copper between the ground bars (bare or green) anyway. Especially if you have a hunk of scrap wire that will reach sitting there doing nothing.
    – Ecnerwal
    Jun 9 at 15:15
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    @manassehkatz-Moving2Codidact yeah - I realized that when I was half way through. Worst case I think I have enough extra cable slack to swap panels extending up but hope I never have to … Jun 9 at 15:51
  • Are the grounding bars installed against a painted surface? If so, the bond connection is only through the screw threads, and screws can corrode over time. -- OTOH I guess if this was a common problem, a tie strap or wire would be required. Jun 9 at 18:05
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    You're 90% full and you only just got the panel. That's a redflag right there, since that feeder can support way more stuff than you've got in there right now. And with the conduit you make it almost too easy to add circuits. (conduits can support up to 4 each). I know the last thing you want to do right now is re-do this whole job with a 24-30 space, but right now is the time, it'll suck much worse when the drywall is up. Future self will say "shoulda listened to Harper"... Jun 9 at 20:51

2 Answers 2


The main thing I see is a panel that is far too small.

Everybody thinks there's a percentage in "scrimping on panel spaces". And then 5 years later they're back here going "Help, I'm out of breaker spaces, what can I do?"

Breaker spaces are cheap. This problem is best solved when you buy the panel. It's an annoying speedbump before you put up the drywall, but it's a nightmare afterward. Given that

  • your feeder is capable of supporting considerably more load than you have in it
  • the feeder is in conduit and could easily be upgraded
  • the branch circuits are in conduit, and conduit can support up to 4 circuits each
  • it is about to be entombed in drywall...

I do not "spend people's money" lightly, but absolutely I think you should replace the panel now (while it's still easy) with a 24-space or 30-space panel that will definitely cover all future needs. (yes I know you say right now that you have no future needs, but everybody says that at the time :)

I would use HOMeline type so a) you can reuse all the expensive xFCI breakers and b) the knockouts at the bottom of the panel are exactly the same. I would also revisit whether the main breaker is necessary - it's not if it's in the same building.

Once it's cemented into drywall the only option for more spaces would be to try to find a QO or HOM panel that has more spaces and uses the same box (such as the old non-PON version of the HOM20M100C) and swap bus assemblies, but that would probably mean having to replace all those xFCI breakers.

Other than that, the only thing I see is ad-hoc breaker numbering, which is bad if it's out of sync with the numbering on the real panel cover, but it looks like you went out of your way to do it correctly.

Last thing I promise, since you're building a house we are seeing people report getting higher offers on their house because they have a welder or RV outlet in their garage, because of electric vehicle anxiety ("if I get one will I be able to power it"). That's worth money to some. Like I say, "I'll never need more than this" is always untrue!

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    Agreed with panel size. I have a lot of space in main 200amp panel - this was a subpanel to service two new bedrooms. I think I'm going to risk deferring upgrade as walls will be shiplap and just a few boards to pop to get back to this state later. Jun 9 at 21:58
  • I'll double check the numbers - but I thought those are the numbers matching the door sticker - note that panel is upside down. I wrote them there to remind myself as I installed, maybe I did mess them up... Jun 9 at 21:59
  • Yeah - noted on the EV comment. I have capacity for that in garage if I need it - what's not clear from the pic is this is an addition that is literally on the edge of a cliff wrapped in rock that took 3 weeks of rock hammering with a giant excavator. No car is ever coming close to this location without some serious investment ;) But yeah - you are right, I screwed up planning and undersized the panel space. Jun 9 at 22:02
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    @BlueGoldfish I think you went out of your way to get the numbers right, that is mostly there for other readers. Jun 9 at 23:05

The only thing I noticed is the pair of NM cables below right.

the one is on its edge that will get flagged. NEC 334.30 flat cables shall not be stapled on edge.

it looks close for 1/4” of insulation inside on the NMB cables,

it looks like you removed the bonding screw for the neutral buss and you have the neutrals and grounds separated.

nicely labeled

The can is usually sufficient to connect the grounding busses (with conduit the can is the connection if no conductor) but if you have some extra #6 I think that is better you have plenty of space.

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    thanks. good catch on staple will double check all my other stapling. Jun 9 at 17:46

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