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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?

isherwood
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Dean
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1 Answers1

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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.

manassehkatz-Moving 2 Codidact
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    Excellent. Thank you for the feed back. I am only running 4/0 4/0 2/0. – Dean May 19 '21 at 20:16
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    @Dean Pardon my asking, but are you just running 220 V? I assume your not running a neutral. – tnknepp May 19 '21 at 20:19
  • I am running 185ft from PUD transformer to a 200amp meter/service panel combo – Dean May 19 '21 at 20:20
  • @Dean Maybe my brain is failing me this late in the day and manassehkatz can set me straight. If the 2/0 is your ground then you still need to run a neutral if you want 120V for anything. If your 2/0 is your neutral then it needs the same current-carrying capacity as your two hots (i.e. has to be same size). I realize this is not relevant to your post, but I'm confused and don't want you to get bit by a mistake. – tnknepp May 19 '21 at 20:34
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    @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. – manassehkatz-Moving 2 Codidact May 19 '21 at 21:47
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    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 '21 at 02:06
  • Aha. I got confused (I was thinking "transformers between buildings on your property') and didn't notice "access road". So essentially you are making your own drop from the power company to the meter. In most places (not being a pro, but as I understand it), that wire is (a) hot/hot/neutral with neutral smaller and no ground, matching your configuration but (b) normally owned and supplied by the power company and not user-supplied/installed. So an unusual (in my very limited experience) situation. – manassehkatz-Moving 2 Codidact May 20 '21 at 02:19
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    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 '21 at 02:48
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    Maybe I should just go 4/0 4/0 4/0 to be safe. I assume a 200 amp meter panel will accept 4/0 wire at all terminals. – Dean May 20 '21 at 02:50
  • The catch is that 4/0-4/0-2/0 happens to have relatively good pricing compared to many other sizes/combinations. – manassehkatz-Moving 2 Codidact May 20 '21 at 02:54
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    Having a smaller neutral is not unusual. the neutral only needs to be big enough to handle the 120V loads, the 240V loads don't touch the neutral. – Jasen May 20 '21 at 11:20