I want to replace my old electric cooktop with a new electric cooktop. The new cooktop is 208/240V. It has 3 threaded wires: red, black, and green.

The metal junction box is 4-wire grounded. It has red, black, white wires and a bare wire grounded to a screw in the box.

Looking at my circuit breaker, the circuit running to this junction box is 120/240V.

Is this something I, not an electrician, can do? If so, is this the proper way to connect:

  • Red to Red
  • Black to Black
  • Green (from appliance) grounded to the same screw as the bare wire (from the circuit)
  • Cap off the white wire (from circuit)
  • 1
    Can you post photos of the inside of the box please? Also, what amperage is the circuit breaker, how many kW is your new cooktop, and are there other things on the same circuit as the cooktop? Mar 7, 2021 at 23:03

1 Answer 1


That is correct wiring. You are in the very good situation of: Had 4-wire, now only need 3-wire. Far more common is either: "Had 3-wire, now need 4-wire" or "Had 3-wire that should have been 4-wire but grandfathered".

The only issue is current requirements. Depending on the size of the existing wires and breaker, you may be in any of the following situations:

  • Everything OK as-is
  • Wire OK but need to put in a larger breaker
  • Wire OK but need to put in a smaller breaker
  • Need to put in larger wire and a larger breaker.

Can't tell which of these 4 situations applies without knowing the specs of the new cooktop, the size of your existing wire and the size of your existing breaker.

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