Considerations when using PVC conduit to run off-grid solar cables through side of detached garage

[Jim in Florida]

So it sounds like I should use EMT for conduit on the roof/building, then do galvanized or stainless for underground. It's a very short run for the underground section - less than 15 feet. Shallower trenching would be nice since there's some cement slabs AND tree stump in the path that I'd rather not excavate. I might even look into above ground options since the position of the solar stands may only be semi-permanent.

And judging by the direction the conversation went, it sounds like the placement of the hole/junction box on the side of the building isn't super important or regulation restricted? The position I sketched should be fine since it works best for my needs? That's the part I'm most concerned about, and most itching to get done so I can at least have wire access between the inside and outside. Any thoughts on that are welcome.

The big box stores mostly sell galvanized EMT. Make sure to connectors are the same type of metal (don’t mix with aluminum if you find it) If using galvanized EMT underground ensure you use wet location connectors (they have blue coloring for quick recognition)

 

[Influencer]

(Didn’t go back and review the plans)

The part I’m not sure about here is whether the hole in the side of the building counts as a penetration for battery fire code. If it goes into habitable space and you have a battery right there on the outside next to that hole then it might be an issue because the battery would be too close to a penetration into habitable space. Windows and doors certainly count as penetrations. I don’t know about smaller holes.

While the building does have power (separate from the battery power that I will use independently), I believe it is considered an 'accessory structure' and not a habitable space. I live on a flag lot, and I believe the house in front of me sold the property behind it and this building used to be a detached garage, though it no longer has a garage door. But I will look into battery fire code.

And the battery will be on the inside of the building, just in case that wasn't clear.

 

[wheelman55]

When I did my system they told me pvc underground and metal above ground. Also recommended 2” pvc to keep the critters from chewing it up.

 

[cs1234]

I might even look into above ground options since the position of the solar stands may only be semi-permanent.

Can rigid be above ground in this situation? Or would it have to be buried to meet code?

 

[zanydroid]

Rigid is OK even when subject to “severe physical damage”

I don’t have a code citation but I think it’s fine as long as it’s not in like a driveway being driven over. Since that has specific underground fill requirements in that case IIRC.

 

[Influencer]

Rigid is OK even when subject to “severe physical damage”

I don’t have a code citation but I think it’s fine as long as it’s not in like a driveway being driven over. Since that has specific underground fill requirements in that case IIRC.

Yeah, I'm leaning towards keeping it above ground at this point. It seems the most ideal in my situation. And it's sounding like I should do galvanized metal for all the conduit both on the house and on the ground - my biggest hesitation is just the increased costs.

 

[Balrog006]

Yeah, I'm leaning towards keeping it above ground at this point. It seems the most ideal in my situation. And it's sounding like I should do galvanized metal for all the conduit both on the house and on the ground - my biggest hesitation is just the increased costs.

With the covid greedflation increases in SCH 40 and 80 PVC, the cost differential between it and galvanized is minimal anymore.

 

[Hedges]

I've had so much experience with galvanized schedule 40 steel pipe rusting out where it enters the ground/concrete here in Texas that I'm hesitant about using rigid direct on the ground. Do you guys find it actually holds up? I would hate to pay that much for 100' of rigid, only to have it rust out across the whole length.

Gas pipe, I saw puffy rust where it came out of the ground so I dug it up and replaced.
I then sawed in half, found it actually had a lot of solid meat.

The rust was bad only where within a couple inches of dirt's surface.
I think if you encased it in concrete to 6" or 12" depth, domed above to shed water, then rigid (or other) steel conduit would last longer. Or any other encapsulant - maybe urethane foam?

 

[GregM]

Removing stickers from PVC fittings.....
I bought a bunch of PVC fittings from Home Depot. As much as I tried, I could not get their labels off each of the fittings.
The wife finally suggested trying a heat gun, and it worked.
You have to experiment a little, but I found that heating the labels with my heat gun soften the glue and I was able to peel the labels off fairly easily.
If any "sticky" remains you can take it off with a paper towel soaked with WD40.
YMMV

 

[Influencer]

I've been distracted by life but I'm back on this project. I'm doing some more brainstorming now. I think I'm going with 3/4 inch galvanized steel EMT for the short conduit run outside.

- For the 'electrical box' / conduit body that will be mounted on the outside of the garage, I currently plant to use this 2-Gang Metallic Weathproof Box (or this one). It has extra holes for expandability. They are steel, so same material as EMT. Hopefully waterproof threaded adaptors for attaching the EMT to these are easy to come by. For simplicity I might just get two of these boxes, for each side of the wall, even though the weatherproof is unnecessary for the inside.

- With new ideas on where to put the battery inside, the conduit box will probably be significantly lower than I placed it in my sketch photo, perhaps half the height. I'm still a little hesitant with punching external holes, but it seems like placement height wise isn't a super big deal. I will cut a very small portion of EMT for the length through the wall and connect it to the boxes on each side.

- Outside, the EMT may go straight on the ground unburied, though I might raise it slightly with some sort of mount so it hopefully lasts a little longer. I'll use watertight compression fittings for the connections.

- With the cost of solar panels dropping so much, I might also get a couple 200 Watt bifacial panels pretty soon. I'm curious how well bifacials will do with my setup where there will be lots of ambient light behind the panels.

I'm kind of thinking out loud here but if anyone has any more thoughts, I appreciate any more input. I'll definitely be doing more cautious research, and taking trips to the hardware store to nail down exactly what I will be using. It's a very small setup, but I'd like to do it (relatively) right so it's expandable later.