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Was curious as I've seen plenty of pages indicating that a 240v circuits don't require neutral... in my head that means a branch circuit but I don't know if that is accurate.

My specific case is that I have 100+ feet of 1/0 aluminum triplex and four 100A subpanels. I'm not sure if the length is enough for all four. All of their branch circuits will be 240V. Everything from the service panel to subpanel to branch circuits is in EMT.

I was going to wire it up with all 4 (L-L-G-N).... but as 240V does not need a neutral... can I turn my triplex into 2-conductors + 6 AWG copper ground?

Being able to cut up the 3rd conductor for run to the last panel would allow me all the length I need for sure.

  • What's the exact identifying text on your triplex? It may not be legal to run in conduit to begin with... – ThreePhaseEel Feb 27 at 12:41
  • Need to know more about that triplex. Please state the type. You can edit your question to add detail. – Harper - Reinstate Monica Feb 27 at 13:36
  • It's Bergen. XLPE USE-2 – Nolan Robidoux Feb 27 at 13:56
  • @NolanRobidoux -- that's not enough, I can't tell from here if it's USE-2 only single-rated overhead or URD triplex, which cannot be used for indoor conduit wiring by Code, or if it's a multi-rated USE-2/RHH/RHW-2 triplex that is legal for indoor conduit wiring by Code – ThreePhaseEel Feb 28 at 0:21
  • Also, is the third wire in the triplex bare or insulated? – ThreePhaseEel Feb 28 at 0:21
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A 240v only panel has no need for a neutral, I have panels in a industrial facility with no neutral, but for residential my jurisdiction requires a 4 wire feed or 3 with conduit as a ground even for all 240v loads. I think this is because someone may try to use the ground buss at a later date so they require it for residential. But industrial since maintained by electricians we don’t have to have a neutral. Each panel in the plant is labeled with the voltage for this reason.

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Parts of the Philippines are wired like the USA. But they are trying to harmonize their power grid to the EU style, so people in those zones must wire like North American 240V-only - with 120V and neutral use forbidden. At some point they will move a jumper on the supply transformer and be full EU. If you are in the Philippines, your plan is fine. Stop reading: this answer is over for you. For everyone else in El NEC territory:

Neutral vs ground matters

Neutral is not ground. It's never ground. It's not even a little ground. Criss-crossing them or using one for the other seems harmless, but it actually creates a time bomb that means a simple loose wire somewhere could kill you. They must be absolutely 100% separate at all times, anywhere but the main panel.

Here is the root problem with 240V-only panels. Sooner or later, somebody will want to stick a 120V circuit in there. Or a 120V/240V circuit (primarily 240V but uses 120V for controls, e.g. a dryer or range). They won't even think about what they're doing; this will seem very natural since you do exactly that in a main panel. At this point, a simple wire problem will create a lethal situation, as above.

Because of this, inspectors generally want you to wire the neutral even if you're not using it, to protect you from that future mistake.

You might as well. You're wasting a wire if you don't.

You already have enough wires to deliver 2 hots + neutral + ground. The trick is, EMT conduit is an acceptable ground path. So the conduit itself delivers safety ground; your smaller wire delivers neutral; and the 2 larger wires deliver hots. Everybody's happy.

You will need to spend $7 on an accessory ground bar for ea--- wait a minute. Didn't you say the entire building is wired in EMT conduit? You're already finished with grounds. EMT is your ground.

Seriously. This is how commercial wiring is done. I have four buildings with 7 panels with 6 services, all done in EMT or busway. None of the panels even have a ground bar. They've been touched by a dozen electricians and many permit/inspection cycles, and nobody's batted an eye or said a word about it. About half of the work is old enough to predate mandatory grounding, and half is post-1980; there's no difference in wiring method. It's all Code legal today except for post-2011 AFCI/GFCI requirements and I refuse to put handle ties on certain breaker-switched, lighting-only MWBCs.

The only time you would ever put a ground wire in an EMT conduit is if you had an expectation that the conduit might take physical damage hard enough to part a coupler. But at that point, you really should be not using EMT there, either better protect the EMT or run Rigid.

Cable in conduit

Is legal, but you'll need a good supply of swear words to pull it. It will be difficult to pull, and we like to warn DIYers both a) about the difficulty of pulling cable, and also the difficulty of any pull that is near the capacity of the conduit. Generally, cable inside conduit should always be avoided; run THWN or XHHW single conductors to suit. But since you already have this....

... Well, hold on. Does your USE cable have markings on each individual wire? Does it easily separate? If so, you can easily separate it, and get to play by the individual-wire rules. Otherwise you're stuck with what follows.

When you have a lumpy or non-round cable, you must treat that (for conduit fill calculations) as a round wire of the large dimension; i.e. what circle will this cable fit inside? CME Wire says 1/0-1/0-2 URD is 1.14" in diameter. Okay. With one wire, the conduit's inside diameter must be 138% of the cable diameter. (technically, that's 53% conduit fill, but what I just said is easier to compute). So for you, 1.57", but you just make it with 1.5" trade size conduit.

  • At 2 cables, you're only allowed 30% fill. So now the conduit must be 259% of the wide dimension to support 2 identical cables. (e.g. 3" conduit for dual 1/0-1/0-2 URD. Ouch).
  • At 3 cables, you're allowed 40% fill, so for three identical cables, 274% of the width of one cable. (still 3" EMT).
  • At 4 cables, conduit derate becomes a concern, but not for your oversize wire. Conduit ID must be 317% of cable width. For you, 3.5" trade size EMT.
  • At 5 cables, conduit derate becomes so severe that it's not worth doing.

Adding an extra ground wire inside the conduit means that would be two "wires", forcing you to 2.5" conduit. Ridiculous. So don't do that; secure the EMT firmly or run a ground wire outside it.

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  • I'm in the US. This is "commercial"-ish. It is a commercial service in a garage. The two 200A main panels are 120V/240V. The subpanels and all their branches are 240V. I know what you mean about difficulty pulling.... Doing two 100A feeders from my house to garage prior to the service install, pushing the conductors through was more effective. Guess I'll see what inspector has to say but whenever I sell the house I'm dismantling the EMT, outlets, boxes, subpanels, etc and reselling what I can. There will be no confusion. :) – Nolan Robidoux Feb 27 at 19:32
  • Conduit derating makes no sense to me. But I'm a DIY'er... I went to the triplex specifically because I was going to run 15 (10-Line 5-Grnd) 10-AWG THHN through 1.5" EMT because I had no intention of doing ten 1/2" runs. I'll running same amps... in less fill... but derate from # of conductors was crazy. – Nolan Robidoux Feb 27 at 19:47
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    @NolanRobidoux You might want to ask more questions; I detect a few misconceptions about conduit derating and grounding. Keep in mind derate computes off the 90C number in 310.15(B)(16), so Does Not Matter for <=4 circuits of <=30A each. So for five circuits, two 1/2" EMTs will suffice; for ten circuits, three will do it. Also you don't need 2 grounds in the same pipe, they can share. Of course EMT needs no ground wires. – Harper - Reinstate Monica Feb 27 at 20:03
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    I wouldn't remove it unless the buyer says "I don't want it" - many will see it as a valuable thing - any Norm Abrams wanna-be, or anyone with plans to get an EV. Big power in the garage? Yes, please. – Harper - Reinstate Monica Feb 27 at 20:06
  • Well unfortunately I've had the equipment for some time and am just now getting around to installing it. My equipment is running off five 30A PDUs at the moment... the wiring would give me the ability to use all of ,my stuff. Definitely will sell it for poo, LoL. The feeders can be reconnected and there are circuits off the service panels with L6-30 outlets that will remain in place. EV lovers can still charge their vehicles. Thank you for the in-depth help. :) – Nolan Robidoux Feb 27 at 20:14

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