I am using 2-1/2" schedule 80 electrical conduit because it is being run along/under my property's dirt access road. From the research I have done and reading fill charts it looks like I can use either schedule 40 or 80 in 2-1/2". I just want to make sure it will meet requirements for fill without any question. Or, do I really need schedule 80?

1 Answer 1


According to table C.9 referenced in this answer, 2-1/2" Schedule 80 can handle up to 5 x 4/0 conductors, so you're fine even for a full hot/hot/neutral/ground (and ground definitely doesn't need to be as big).

Actually, it isn't exactly like that. 4/0-4/0-4/0-2/0 cable probably takes a bit more than the individual wires, but is relatively round (which helps) and I found plenty of references to running it through 2" conduit, so 2-1/2" gives you a little more room to work with.

  • 1
    Excellent. Thank you for the feed back. I am only running 4/0 4/0 2/0.
    – Dean
    May 19, 2021 at 20:16
  • 1
    @Dean Pardon my asking, but are you just running 220 V? I assume your not running a neutral.
    – tnknepp
    May 19, 2021 at 20:19
  • 1
    @tnknepp Generally speaking, you are correct. The only catch is there might be some downsizing allowed on the neutral once you hit a certain size, based on the usage normally being at least somewhat balanced. But I don't know the specifics on that. But since OP stated "transformer", this is likely hot/hot/ground, with neutral provided as transformer center-tap at the destination. May 19, 2021 at 21:47
  • 2
    I spoke with the lead inspector at the L&I. I explained to him that my electrician said I needed 4/0 all same size. He told me they do not require the neutral to but upsized. So, 4/0 4/0 2/0. The 2/0 is neutral. No ground needed coming from Transformer to Meter/panel combo. But 2 ground rods at panel.
    – Dean
    May 20, 2021 at 2:06
  • 2
    PUD is running their wire from what they called a distribution box at the road to a Transformer they are installing on my property. From transformer it is my responsibility to run wire to my meter/panel. They said they are little different, where the wire from transformer to meter/panel is owner responsibility. Even the PUD said 4/0 4/0 2/0, but because they follow their own rules it was suggested I ask a licensed electrician. I asked the electrician I am mostly consulting with and he said 4/0 4/0 4/0. I asked L&I who has to buy it off and they said they do not require up size on neutral.
    – Dean
    May 20, 2021 at 2:48

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.