What happens if you get the red and black wires of a four prong dryer cord backwards?

This question assumes:

  • we are talking about U.S. Residential wiring
  • the person doing the wiring gets the green and white wires in the right place
  • 3
    Nothing whatsoever happens.
    – Ecnerwal
    May 29, 2014 at 3:04

2 Answers 2


Assuming you are asking about US residential biphase 240 volt wiring (or equivelant), then there is nothing wrong with reversing the black and red wires.

  • Ok. I appreciate this help because I'm switching out a 3 prong cord for a 4 prong cord and the connections for the "red" and "black" wires aren't clearly identified.
    – user21806
    May 29, 2014 at 1:55
  • The usual markings are L1, L2, N, and G. If that's what you have, then usually L1 is black and L2 is red.
    – longneck
    May 29, 2014 at 2:21

To clarify, there is really no such thing as them being backwards. Red/black, black/red, X/Y, black/black; it's all the same thing.

This is why you'll never see them identified by color. Typically in a 4-wire installation like this (NEMA 14-30 in this case) the two hots will be identified simply as X & Y.

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