Solar 2020 Part 8: Underground Conduit and DC Wire Pulls

The worst part of the project, easily, was doing the conduit work.  It was the middle of summer, the air was thick with smoke from the fires all over the west coast, and I was outside doing an awful lot of digging with a pickaxe and trenching shovel.

This is a companion discussion topic for the original entry at

Hello, this is super helpful. I had no idea the conduit needed to go straight up from the ground. Or that conduit had a limit of 360 degrees in a single segment.

There’s so much uncertainty with DIY solar, and lack of help from the authority having jurisdictions, it’s really disappointing. But blogs like this are helpful.

:boom: :boom: :zap: :zap:

I’m in Florida working through ground-mount residential permitting uncertainty and will get to conduit soon. Thanks for posting your experiences.

Welcome! Glad it’s been of use.

This is a “local understanding” sort of thing. The 2017 NEC refers to DC power conduit on or in a building - so, per the writing of code, I might not be able to have inverters on the side of my house. Is a free standing conduit between the ground and the inverter “on or in” the building? Ask your local inspector. The other option was to hang the inverters out on the frames, and run AC into the building underground.

That’s straight up NEC and I don’t think you’re going to find local understandings of that. Buy a copy. Read it. There’s a good reason for that, involving pulling forces and damaging insulation. Use wire lube.

I can’t argue there, though I’ve not gotten around to writing a book on the matter. Sorry, too many projects in my life.

You’re welcome! Feel free to post your system designs in more detail, and I know a few people are happy to beat up on it from a NEC-informed perspective!

Wire lube sounds smart. I’ve got a copy of the NEC2020 code from the free version online.

My biggest barrier now is getting past the residential building permit.

The electrical guys don’t even come into play until I get a structural drawing signed and sealed by a structural PE.

There’s very little comparison shopping here because nobody really talks about PE design drawings.

I’ve had quotes from $5000, to $3000, to $2500, to $1500, but I have no reference to gauge if these are good or bad.

I’m using a standard IronRidge kit 5-up and 6 wide with the XR1000 rails. The manufacturer provides drawings in pdf format and also in Autocad .dwg format. So drawings aren’t the real cost. It’s structural evaluation.

There are 2 differences in my system as-designed vs. as-built:
(1) ground depth for concrete and holes was supposed to be 6.5 feet. I dug 4 feet.
(2) steel pipe was supposed to be ASTM A-53 Grade B but my pipe arrived A53 Grade A. I didn’t even notice until it was built.

What’s the going rate for PE-stamped drawings?

“Your mileage may vary” answers are not helpful. There’s really no market or way to judge if I’m getting a good deal or bad deal.

How is anyone supposed to know if there’s no reference available in the marketplace?

Unfortunately, this is why the solar installers can get away with the $4/W stuff. Because they know the local systems.

I don’t suppose you can find the plans for your house on file anywhere and get the roof design loading from them?