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Help wiring 220V stovetop when supply wires are not color coded

Help wiring 220V stovetop when supply wires are not color coded

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Old 12-10-07, 05:46 PM
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Help wiring 220V stovetop when supply wires are not color coded

My son is in the process of replacing his stovetop range. Unfortunately, he didn't mark the power supply wires when he removed the original stove. The new stove has three wires (black, red, and green). But the power supply has four wires (3 black, 1 bare connected to the junction box). How do we determine which of the black wires to connect each colored wire to? The stove comes with clear directions: "connect the black to the black, the red to the red, etc." Thanks!
 
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Old 12-10-07, 06:33 PM
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Use a voltmeter to test the three black wires. If you are in North America, you will find that
A to B is 120 volts.
A to C is 120 volts.
B to C is 240 volts.

The B and C wires will be the two hots (and red vs. black makes no difference). The A wire is the neutral, and the green wire is ground.

Alternatively, you can use a non-contact voltage tick tester. The two wires that tick the tester are B and C, and the one that doesn't is A.

If your stove is brand new, and does not contain alternate instructions for three and four wire connections, then you will leave the A wire unconnected. If your stove does have alternate instructions for a four-wire connection, then you'll need to replace the cord on the stove according to the directions.

If you have no directions with the new stove, find some. It's important.

Note that using three black wires is a code violation.
 
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Old 12-10-07, 07:43 PM
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Originally Posted by John Nelson View Post
Note that using three black wires is a code violation.

For your installation. Two blacks, one white and one green/bare/green with yellow stripe would be correct.
 
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Old 12-11-07, 11:50 AM
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Smile Just what I needed! Thanks!

That was just the information I needed, thank you!

I don't know why the supply cable isn't up to code given that the house is all of 10 years old. Maybe I'm missing something?

In any event, your directions are clear and I'm sure we'll figure which wires are hot and which is neutral using a voltmeter. The stove is new, comes with 3 wires (red, black, and green) and clear instructions for hooking up to a 4 wire supply (the green ties into the ground at the junction box, the red and black go to the hot wires, and the neutral supply wire is capped).

Thanks again!
 
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Old 12-11-07, 06:58 PM
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What size breaker is protecting the existing 4 wire cable?
 
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Old 12-12-07, 10:18 PM
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I believe it is 50 amp, but it could be as low as 30 amp (this is for my son's house and I haven't been in the breaker box in a couple of weeks).
 
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Old 12-12-07, 10:47 PM
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I was thinking that it might be a 50. It would be rare that you will need that big of a breaker for the stovetop and I am assuming here we are talking about a "cooktop" and no oven. You probably have 6 awg ran for wires. the wiring will be ok though probably bigger than needed. The breaker will need to be sized for the wattage of the cooktop i'm betting it will be a 30 amp breaker. Generally the breaker protects the branch circuit conductors but in your case the wire likely is oversized because old range was a bigger load demand and the breaker will need to be sized to the load of the new cooktop. I think this link is what you will be doing for you son.......

 
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