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Unincorporated Pierce County, Washington State, USA.

We're covered under Washington State L&I for electrical inspections and I've been digging around their site but have failed to come up with an answer. This is honestly probably a stupid question but I'm going to ask it anyway.

We're building a detached shop/ADU and laying 2 inch conduit from our main structure out to the new building and bedding it in about 5" of sand. We need to have a ditch inspection before we backfill. However what I cant seem to find is, do we actually need to have wire in the conduit, or can it be empty for the inspection.

Reason being, we're not ready to make the full run yet, but need to backfill our trench as its blocking access to the worksite. Essentially I want to leave the conduit stubbed out above ground level next to the main house and complete that section later. Plus pulling 2/0 2/0 2/0 AL and #6 ground that entire distance sounds like a major PITA. It would be nice to pull from the new structure to where it comes out of the ground, and then finish the pull from that point.

Since I'm on the topic of conduit and this feeder, maybe someone can tag a separate answer on. From where the new feeder comes out of the ground, we're going to run it up the side of the house and into our attic using a conduit body to make the 90* turn in. Coming out of our main panel the previous builder put 2 inch conduit up into our attic for us for future use. From where the old conduit ends, to where the new conduit enters the house, I was planning on leaving the wires exposed in the attic, would this be acceptable, and if so, what method of stapling would you use? None of the staples I've seen allow for wire up to 2/0 in size.

  • Is 5 inches sufficiently deep or is 5" just the sand you are laying it on? 5" can easily be hit by any monkey hammering in a post... – Solar Mike May 8 at 6:48
  • What type of conduit are you laying here? – ThreePhaseEel May 8 at 11:43
  • I guess I wasn’t clear (I blame it on the beer) 4 foot deep trench with 5” of sand at the bottom. Sch 40 PVC conduit. – Chris May 8 at 15:32
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    You may need schedule 80 where you come out of the ground, up 4-6 feet, as that area is considered "exposed to damage" or similar language - or you can protect it some other way, but that's the typical simplest/cheapest way. – Ecnerwal May 8 at 18:11
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Conduit in place should be fine for the inspection.

The forces involved in pulling make doing so without the conduit buried (so it stays put) rather difficult, and in any case it's quite common (and it you have not, I suggest you go get some) to put empty conduits in a trench for future use (i.e. a small conduit for network/phone/communications.)

I have to assume that something makes it worth the extra run up to and down from the attic rather than simply entering the building on the level of the main panel.

I would NOT leave the wires exposed in the attic. I'm dubious that it's acceptable, as they are not cable, designed for exposed use, but in any case I would not do it. I've seen way too many chewed cables in attic spaces. Completing the run in conduit should not be terribly difficult, and gives the wires protection.

  • You are correct that exposed wires outside of a cable or conduit would be unacceptable here, see NEC 300.3(A). – ThreePhaseEel May 8 at 11:46

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