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Steve G.
Steve G. , Handyman
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We are replacing a stove with an oven and a separate cook top.

Resolved Question:

We are replacing a stove with an oven and a separate cook top. The power line for the old stove has the expected four wires: two hot ( black and red ), white " return" and green ground. The new oven also has a power cord with the same four wires. But the cook top only has three wires: hot black and red and a green ground. The installation instruction say to connect the black to black and red to red and the green to ground. How does that work without the white return? The line from the main panel to connect to the cook top does, of course have the four wires. What do I do with the white coming from the panel. Isn' the white needed to complete the circuit ?
Submitted: 3 years ago.
Category: Home Improvement
Expert:  Steve G. replied 3 years ago.

Hello there and welcome to Just Answer. My name is XXXXX XXXXX I will be assisting you today. I am an engineer with over 30 years of electrical and electronic training, repair and installation experience. I will try and answer your question accurately and precisely so that we can get you on your way.

In a 4 wire system i.e. two hots, a neutral and a ground, and in a residential electrical system, you can derive both 240V and 120V from the same set of wires.

If you measure the voltage from either of the hots to the neutral, you will get 120V. Across the two hots and you have 240V because the two 120V sine waves are 180 degrees out of phase with each other. Think of it as +120V and -120V. The difference is 240V.

Your old stove and you new oven uses the 240V for the heating elements and probably uses the 120V for the controls, lights etc. The new cook top only needs 240V so therefore no neutral is required.

I hope that explains it for you. Let me know if you need more help.

Steve

Customer: replied 3 years ago.

Ok I understand the theory/principle. Now for the practical:
Right now the four wires coming from the panel are connected to the panel with the black and the red into one 40 trip switch fuse each and the white Just to the neutral bar. The two trip fuses are connected to one handle. If I connect the three wires of the cook top to the outgoing four wire what happens to the white? It is connected to the bar of the panel, but has no connection where I connect the cook top power word to the line to the panel. Would it be best to run the cook top wires to a plug and the wires from the panel to an outlet rather than connecting directly. It would still leave the white an orphan.
Expert:  Steve G. replied 3 years ago.

You can either disconnect the white at the panel or do what most people would do and simply wire nut and tape the neutral conductor at the outlet box. As it is right now, you can touch the neutral. It carries no voltage or current. It is safe but you want to tape it up in the box so that it doesn't make contact with any other wire and cause a short.

This is done all the time and completely within code.

Steve

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