I'm rewiring some 2"x2" solar panels, I see the place the wires are supposed to be connected, and they're marked with a "+" and a "-" sign. I look through my bin of wires, and see a bunch that will work for me (two wires joined together so that one is positive and the other negative).

However, some have a black wire and a white one, some are black and yellow, some are yellow and black, red and white, both the same... In the case that they are both the same color, I've marked one wire myself.

Is there a standard for which color should be positive? For example, you have two wires that are the same color, but one is knotted at the ends. Is there a standard that says something like "the knotted one is always negative" or "red is positive".

I know that if there is a high risk involved, then I shouldn't make an assumption, but is there a "right" way?

  • Make sure these panels actually are comparable: raw panel vs. internally regulated panel to charge X volt battery of Y chemistry vs. grid-tied with onboard inverter etc. Nov 8 '17 at 17:56
  • no, knots don't have a preset meaning, and neither do stripes. make sure it's clear or use a meter.
    – dandavis
    Nov 8 '17 at 21:22
  • If two wires are the same color, either look for ribs or other distinguishijng features on one of the wires... Or if they are identical, it is surely supplying AC. No one competent would outfeed, say, 2 black wires out of a DC panel. Don't buy their panels! Nov 9 '17 at 19:36

If one of the conductors is intentionally grounded then the National Electrical Code requires that it be colored white or gray. Refer to Article 200 for the grounded conductor and Article 690 for the PV system.

For ungrounded DC conductors supplying circuits operating at more than 60 volts the 2017 National Electrical Code requires red for positive and black for negative or other methods that are described in Article 210.5(C)(2) for branch circuit wires and 215.12(C)(2) for feeders as ThreePhaseEel points out in the comments below.

Good luck!

  • 2
    Actually, the NEC enforces red for positive-ungrounded DC and black for negative-ungrounded DC Nov 8 '17 at 23:17
  • @ThreePhaseEel perhaps you can help me with a Code reference for that. I have read back through NEC 2017 Article 690, especially 690.31(B) Identification and Grouping and cannot find any particular color requirement. Maybe it is elsewhere?
    – ArchonOSX
    Nov 9 '17 at 8:13
  • That's because it is indeed elsewhere -- 210.5(C)(2) for branch circuit wires and 215.12(C)(2) for feeders (can't find an equivalent requirement in Art. 230 tho. Apparently nobody's getting their DC from Con Ed any longer?) Nov 9 '17 at 12:45
  • @ThreePhaseEel Ahhh yes I see now. Thank you very much I will update my answer and remember that for future reference.
    – ArchonOSX
    Nov 9 '17 at 16:54

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