The old SEU wiring in my box has a black and red cable, but I have also seen newer SEU service cable where both 120v legs were black.

2 Answers 2


No, there is no "positive or negative" or "left and right" or whatever. This is the same when hooking up a 240v appliance. The two legs don't matter and there is often no way to differentiate the legs other than maybe black and red.

  • 1
    – JACK
    Apr 16, 2020 at 19:57
  • I assumed there was no specific order for single phase, but better to ask the community and get a consensus. I'm actually surprised that in roughly an hour of Google searching I could not find any forum/blog/article that specifically touched upon this exact topic.
    – roasthead
    Apr 16, 2020 at 20:32
  • 1
    Yeah I know. I have an installation with 2 conduits between the panel and the machine shop. One conduit has 20A circuits. The other conduit has four 30A circuits arranged B-R, B-R, B-R, and B-R. In the bottom of the panel and splice box are a bunch of wire markers that fell off. Imma rearrange them B-B, R-R conduit 1, B-B, R-R conduit 2. Apr 17, 2020 at 0:17

Yeah, in split-phase, nobody cares what color the hots are.

I've seen people go in backflips to have red and black. It's just not necessary.

Of course in cables, it's best-practice to do something to distinguish conductors. You never know what the application will be.

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