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So I'm having some problems planning the last step of my electric run to my detached garage subpanel. I'm using 2 inch pvc buried with individual 1 gauge aluminum conductors (and a 2 gauge ground).

The garage was just built, so open walls and such. I'd kinda like to mount the subpanel between the studs and have all wiring be behind the wall. My understanding though is that since I'm using individual conductors, they have to be in an approved raceway, like PVC. 90 degree pvc bends are very large. Each one is about a foot. I'm not sure what my options are. My state uses 2014 NEC.

I was thinking:

  • Two LB conduit body boxes, one on each side of wall to make kind of a U? 2" ones are pretty massive so I may need to downsize to 1.5".
  • Two 45 degree angles may work, but the hole would be difficult for me to drill at an angle, or kinda large (i.e. out of the ground, 45 into structure, 45 on other side to straighten it out into subpanel).
  • I've thought about switching to a SER cable near the end, but I'm not sure how to properly join large gauge aluminum connectors. Would I be able to switch it in a conduit body piece above ground outside the structure?
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    The PVC conduit could come up the wall and then straight into the back of the breaker panel. Or are you trying to avoid that? – JPhi1618 Jan 31 '20 at 21:44
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    Why not go directly into the panel? A sweep is needed to go from your buried conduit up. Then an LB directly into the box with a nipple. Remember you cannot have more than 360 deg of bends between pulls like the LB and 270 is tough even with soap (lubrication). + you do not want a splice , that would add underground splices $$$. – Ed Beal Jan 31 '20 at 22:15
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    If it's cold where you are, and if you're insulating, and if you're planning to heat the garage at any point in the future, I really wouldn't put the panel between the studs - it should be mounted on the wall. Insulation and vapour barrier should go in the wall. – J... Feb 1 '20 at 15:09
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I'd do (and have done) Ed's suggestion of up the wall a then LB (or LR, LL) straight into the back of the box. It works, no fuss, no muss.

If you want to come in lower for some reason, I'd stay with PVC on the exterior but transition to a metallic product (EMT, IMC, RMC) once in out of the weather. Among other things, a lot more compact than their PVC friends for the same "size product"

A handy thing I've only just now seen in PVC (but was familiar with from metal) is a "pulling elbow." Oddly called an "access elbow" for some reason in PVC?

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Those are a lot more compact than an LB.

Making some assumptions about your wire insulation, I also see that your conduit fill % is quite low (generally good for pulling) but that does mean you could switch to a smaller size for the presumably short section inside the building without violating 40% fill. 1-1/4 EMT or PVC-40 would appear to work (with the assumptions I'm making, basically XHHW insulation) - you need PVC 80 where subject to physical damage, but if you are already in 2" outside that's fine if the inside is protected by being in the wall.

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The question seems to imply a desire to keep the outdoor conduit as low to the ground as possible. Is that correct?

You could mount a NEMA type 1 enclosure inside the wall down low. Use an LB or other right-angle conduit body to connect from the outdoor conduit through the wall into the enclosure. From the enclosure up to the panel you could install a conduit or a cable.

Conductors can't be spliced in a conduit body because bodies aren't sized large enough to allow that (fill rules). You could splice in a suitably sized NEMA 1 enclosure, though. Or you may be able to use conductors that are suitable for the entire indoor and outdoor run -- in this case the enclosure would be merely a pull box that integrates much more nicely in the finished wall (as compared to using a second LB body).

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The simplest way is to come up to an outside wall, then mount the panel on the inside wall on the other side. That way you come up the wall, go through an LB conduit body, and into the back of the panel.

You cannot splice inside a conduit body. Or to be more precise, you can, but then you have to satisfy the cubic-inch and bending-radius requirements of a junction box, so while the catalog may call it a conduit body, the rules of junction boxes apply to it.

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  • Not quite: the exterior disconnect requirement in NEC 2020 is only for services, not for feeders to detached structures (we know this because it's in Art. 230, with no corresponding requirement in Art. 225). – ThreePhaseEel Feb 1 '20 at 0:29
  • @ThreePhaseEel Oh, that's good. Clearly I'm panicking! – Harper - Reinstate Monica Feb 1 '20 at 3:24
  • That's interesting 3ph, I ran across this flyer which said all "dwelling units" required an exterior disconnect, maybe detached structures such as a pump house, barn or detached garage wouldn't be included. But from what I understand from this flyer, if it's an occupied structure, it requires an exterior disconnect. esfi.org/resource/2020-national-electrical-code-731 – George Anderson Feb 1 '20 at 8:23

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