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I have a main panel (200A and an adjacent subpanel that was installed when an addition needed more breaker spaces. The work I am doing is on the interior of the garage's concrete block wall. The total run is 15 feet and is straight from the main panel (on the same wall). Conduit is 3/4" PVC.

The circuits are one 3 w g #10 30A 240V, THHN stranded, one 2 w g #12 120V THHN stranded, both on breakers in the subpanel and one 2 w g #14 wire (have not purchased the wire and currently only have NM-B and UF on hand) on a breaker in the main panel. The #12 circuit will have an initial GFCI outlet, an outlet in the middle of the run, and an outlet at the end. The #10 circuit ends in an outlet (4x4 surface mount box), and the #14 supplies a switch to be mounted with the aforementioned 120V outlet in a second 4x4 surface mount box adjacent to the one for the 24V outlet.

The questions are:
What is the best practice for identifying each circuit in the run?
Wrap or zip tie each circuit in a bundle, or better to mark each wire with its circuit identifier? Neutrals and grounds must go to their respective panels, but if some or all of the grounds are bare doesn't this compromise keeping the grounds segregated by panel? A comment on this board quoted a NEC rule that an insulated ground must have a continuous green or green/yellow striping, All of my stranded wire is white, red or black, as I intended to "mark" a white as ground, but that seems to be a code violation, and if I should not use bare grounds then it looks like I'll needs some green in correct sizes from HD "buy the foot"? Other advice to make this a "good" installation is much appreciated.

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  • You are in an unusual situation in that you have 3 circuits on 2 panels with 3 different wire sizes. So you may not even need to mark the wires - 10, 12 and 14 are each different circuits. But I don't know the answer to the ground wire question, so just a comment. Jul 1, 2022 at 16:37
  • You sure ground has to go to a particular panel? What if you have a metal box with two circuits from two panels? How do you ground the box itself? Surely all the grounds get tied together, no?
    – jay613
    Jul 1, 2022 at 18:43

2 Answers 2

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Regarding marking the circuits of the wires, it can't hurt, and could help you in the future, or the next person if they choose to believe your markings. There are many methods available to mark wires that should work fine. Your setup is similar to having several circuits' worth of Romex running up one stud bay in a wall. Ultimately, the wisest thing would be to check using the usual methods to determine which breaker runs which set of wires.

If the conduit is metal, properly assembled, and properly grounded either by running back to the grounded panel/subpanel or by a code-compliant ground connection, then you don't need a separate ground wire in the conduit. But you could run a separate bare copper ground through the conduit too, according to NEC NEC 310.2(A) and 250.119. (web-searched through https://forums.mikeholt.com/threads/bare-ground-in-conduit.10968/)

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  • "If the conduit is metal" - correct, but OP stated Conduit is 3/4" PVC Jul 1, 2022 at 19:17
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    Oops! Missed that, thanks, @manassehkatz! And it was at the end of a paragraph, too. Jul 1, 2022 at 19:24
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You are not allowed to re-designate individual wires into a different category (unless the wires are #4 or larger).

  • neutrals must be natively white or gray jacket
  • grounds must be natively green, yellow/green or bare
  • hots must be any other native color

Only in jacketed cable can a neutral color (only) be re-designated a hot color (only). However the cable may be inside conduit if you can handle the enormous conduit fill that non-round cable requires.

Too bad it isn't EMT metal conduit, would save you 3 ground wires. It isn't critical to keep grounds from different panels separated, obviously that does not happen when EMT, RMC or IMC conduit shell is carrying the ground.

"PVC is cheaper than EMT" I would fact check that. Not in my experience.

Since colored tape is not allowed to re-designate white wires to hot, a hot color on a white wire can be used to associate it. White/blue is blue's neutral. "That was easy"

Note that in a 240V circuit, there is no need to distinguish hot wires from each other. Thus it is legit to use 2 of the same color hot, and actually aids circuit identification.

Most better hardware stores and lumberyards will cheerfully sell you THHN wire by the foot, in any color you want, as long as it isn't yellow, purple, gray or pink or sometimes brown. They often have orange; it is the one mandatory color in the whole NEC. (For 3-phase "wild leg delta" installations).

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    Have to agree with you. If the 3/4 pvc isn't installed yet (it's gotten ridiculously expensive), return it and get EMT The run is so short I'd def go with EMT avoiding the cost of the ground wires. Jul 1, 2022 at 21:07

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