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I have a 25’ run from an outdoor meter/breaker to feed a 200 amp main panel (NEC 2020).

About 15’ of the run is through this 2.5" PVC pipe underground. It runs under the garage and into the crawlspace. It just comes up through the dirt like this–looks like someone just took a hacksaw to it. Two questions:

  1. Which cable should I run through this? (three 3/0 copper + one 4AWG ground, or something like USE, SE, SER, RHW, etc)
  2. How could I properly transition from the dirt to the joists, to continue to the panel? There's about 2 feet between dirt and joists.

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House details:

  • Built in 1989, 200amp service, UG service entrance, PG&E utility, California
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  • Almost always aluminum, not copper, at those sizes. Aluminum 4/0 and (I think) 4 for the ground. But cable type is a big issue. Individual wires might be better, but whether that is even possible depends on whether that PVC is conduit or just plumbing pipe. If it is just plumbing pipe then it works for physical protection but can't be used with individual wires, only with cables. Commented Dec 6, 2023 at 22:27

2 Answers 2

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A hacksaw is the normal way of cutting conduit. A tubing cutter leaves a heinous burr which then tears at wires while being pulled.

First, for feeder of this size you should be using aluminum. Using copper is pointless; the lugs at both ends are tin plated aluminum. Aluminum feeder in these large sizes has proven reliable. Using aluminum rated terminals and torquing to spec makes all the difference in the world.

Use 250 kcmil unless your service size is itself 200A and the service is to a dwelling, in which case the more common 4/0 will suffice.

SER and SEU are not allowed underground unless it is specifically rated for that.

MH feeder (typ. RHH/RHW) is allowed underground, but it is not allowed inside walls without being in conduit.

You need 4-wire, unless you are declaring your outside disconnect to be "emergency disconnect, not service equipment" per 230.82.

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To my knowledge there are no completely compliant solutions to installing feeders like this partially in conduit underground and partially unprotected. As pointed out, SER can be run unprotected in the walls but not underground. THHN, THWN,etc., Can be used underground in conduit but not unprotected in structure. USE/URD can be run unprotected underground (direct buried) but not in structure. Your best option is to complete the conduit run to the panel and use a 4/0 URD (codename Sweetbriar) + #6 Cu ground wire. Unless there is a state/local prohibition on Al wire, in which case 2/0 Cu THHN should be used.

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  • Incorrect! Encore Wire makes a dual-rated SER/TC-ER cable that can be used for this purpose. Commented Dec 7, 2023 at 3:47
  • Thank you for that information! I will add that one to my notebook.
    – Keith
    Commented Dec 7, 2023 at 5:52

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