My cooktop has black, red and bare ground wires (brand new pre wired this way). Power supply has a neutral and no ground. Do I just leave it disconnected as shown? Is this connected correctly? Or should I greentape the unused neutral wire and connect to ground at panel and to bare wire from cooktop at juntion box. see picture.
You can’t re-mark or tape a neutral to turn it into a ground, per NEC 250.119:
Individually covered or insulated equipment grounding conductors shall have a continuous outer finish that is either green or green with one or more yellow stripes, except as permitted in this section.
The exceptions are for
- conductors 4 AWG and larger
- conductors inside multiconductor cable
Your situation doesn’t fit in these three exceptions, so you have to run a new ground wire. Luckily, you have a conduit, so it shouldn’t be hard.
Note that if the conduit is intact all the way back to the breaker box, it is in fact a legitimate safety ground path, and you can ground the cooktop by attaching its ground wire to the box.
In fact, in your photo it appears someone has already done exactly that; the bare copper ground wire from the upper conduit goes to a screw attaching it to the box.