I’m installing a new induction cooktop to replace an old electric coil unit. The new unit has a three-wire connection (black & red hots and a green ground) with instructions for retrofit to existing three or four wire box connections (with or without a neutral wire). House was built in the 1970’s.
The old cooktop was connected with black & red hots, a white neutral and a ground to the junction box (which does not have a ground wire back to the panel but may have a ground path via the conduit - but I don’t know for sure), so it’s kinda in-between the cases in the instructions (both assume there is a grounding wire).
My initial thought was to hook up red-red, Black-Black, green (cooktop ground)-white (house neutral) roughly in-line with the four-wire retrofit instructions. Would this be my best (safest) bet or would it be advisable to attach the cooktop ground to the junction box (although I’m not sure how I ensure the box is a good ground) and cap off neutral? I suppose I could also attach the house neutral and cooktop ground to the junction box grounding screw as a “belt-and-suspenders” approach but I don’t know if that introduces other risks?