How to hardwire 240 volt electric cooktop. From house conduit is 2 black and 1 white wire. The cooktop has 1 black, 1 red and 1 copper. My old one is from house black to cooktop black, from house black to cooktop red, from house white to cooktop copper. I thought white was neutral, but it is currently connected to ground wire. Not sure I should hardwire the new one the same way.enter image description here

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    The problem is you are not allowed to use white for ground, or ground for neutral. The white in the panel should be connected to the neutral bar, which just might also connect to ground. The good thing is that you seem to use conduit instead of cable so pulling a proper ground should be easier, than replacing a cable. The white wire in the picture also looks to have damage, insulation chewed off/missing or just black marks.
    – crip659
    Aug 5 at 23:49
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    If you do have metal conduit all the way to the panel, then you can use that is it is good. Just cap off the white wire. A multimeter that gives a reading of 120v between hot/black and conduit will be good.
    – crip659
    Aug 6 at 0:07
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    the conduit nut is installed backward ... the ears on the nut should bite into the box when tightened
    – jsotola
    Aug 6 at 0:27
  • I am surprised those red wire nuts will accomodate two wires rated for 40 A. I would think you would need the gray wire nuts. What size wires are you connecting? Aug 6 at 4:00
  • crip659, If I cap off the white, then what do I do with the ground from the cooktop? I probably have no business attempting this.
    – Gail
    Aug 6 at 14:01

1 Answer 1


If the supply wires are in metal conduit, that should presumably supply all the grounding needed. The neutral white wire should be capped off, the bare wire from the cooktop should be secured to the metal box with a #10-32 grounding screw. The locknut on the cooktop conduit adapter is upside down and nowhere near tightened enough.

  • To use the conduit as a ground you need to verify the conduit is intact to the panel, use an ohmmeter to verify near 0 ohms from the white to the box and verify the circuit wires leaving the electrical panel are a match and the leave via a metal conduit. I'm concerned you may have an extension of a legacy 3 wire 250.140(B) grounded via neutral circuit, and they didn't ground to the box because the box isn't grounded. If things don't match post a new question probing further clarity and action needed to make legal and safe. Aug 7 at 1:48
  • Not only is the locknut upside down, but the set screw is missing. Probably not a problem, your new stovetop should come with a new connector. Aug 7 at 2:03

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