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Old 11-12-2007, 01:57 PM   #1
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3 wire to 4 wire question


Hello
I have a 3 wire cooktop and a 4 wire from the breaker box (30 amp) please tell me how to connect these together.
Thank you

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Old 11-12-2007, 03:39 PM   #2
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3 wire to 4 wire question


Call in someone with electrical experience. This isn't something for someone inexperienced.
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Old 11-12-2007, 06:20 PM   #3
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3 wire to 4 wire question


Post in electrical. We will determine if you are smart enough. But you got to be smart enough to post in electrical, for sure.
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Old 11-12-2007, 07:28 PM   #4
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3 wire to 4 wire question


Quote:
Post in electrical. We will determine if you are smart enough. But you got to be smart enough to post in electrical, for sure
????



Please post the electrical requirements of your new cooktop. There is a nameplate on it somewhere... give us everything on it that has to do with voltage and watts and amperage. Or give us the maker and models #. We have to make sure the wire size and breaker are correct for the cooktop.

It's a simple deal once we have this information.
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Old 11-12-2007, 07:56 PM   #5
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It was Introductions when I posted that, Stub.
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Old 11-12-2007, 07:57 PM   #6
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3 wire to 4 wire question


As Stubbie said... It's simple once we have more info.
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Old 11-12-2007, 08:27 PM   #7
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3 wire to 4 wire question


I'm sorry for posting in the wrong area I'm new to this forum.
It's a Wolf 15" Induction Cooktop.

Electrical Supply Requirements 240/208 V AC, 60 Hz
20 amp dedicated circuit

The Wolf 15" (381) integrated induction
cooktop requires a separate, grounded 3-wire
240/208 V AC, 60 Hz, 20 amp service with its
own circuit breaker. It has a 4' (1.2 m) flexible
3-wire conduit for connection at the electrical
supply.
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Old 11-12-2007, 09:30 PM   #8
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3 wire to 4 wire question


Hi Mouse and welcome to the electrical forum

Thats what we needed

Your 4 wires coming from the outlet should be red, black, white and bare or green. If not post back with what you have. I am also assuming that whatever was hooked up to the 4 wire worked correctly.


This is what you should have


Turn off the 30 amp double pole breaker. Make sure no one is going to turn it back on while your working.

You need to verify that you have at least 12 awg copper wire on the 4 wire branch circuit you probably have 10 awg.

What you have is a 4 wire 120/240 volt branch circuit from the breaker box. The white wire will be unused in your case. Do not connect anything to the white wire even if the cooktop has a white wire. Just cap the white wire coming from the breaker panel off with a wire nut (just like the image shows). Now just connect red to red, black to black and then connect the remaining ground wires to each other. You may also need to connect a grounding jumper to the box if it is metal (very important). Your cooktop should have a red wire, black wire and a bare or green ground. It may have a white wire and black wire if so these are both used as hots... your cooktop does not need a neutral. If it has a white wire connect it to the red coming out of the wall box and the black to the black. The grounds as I described.
Now at the breaker box you need to change the 30 amp breaker to a 20 amp double pole breaker. And connect the same two wires that you removed from the 30 amp breaker to it. If you are not familiar or comfortable with this part hire an electrician. If you do it be sure to turn off the main breaker any breaker you remove should be in the off position before touching or disconnecting the wires. While your in the breaker box verify that the white wire going to the cooktop location is connected to the neutral bar and not the breaker.

good luck
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Old 04-14-2008, 11:15 PM   #9
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Thanks Stubbie for a very detailed response to the original question. I have a similar situation and will follow your advice.

My question is from a different perspective. While my new cooktop has the 3-wire setup, the old (probably 15+ years) Jenn-air cooktop had a 4-wire connection (1 black, 1 red, 1 white and 1 bare ground). Why the difference? Especially on a brand new cooktop. I thought the new code was for added safety. Is there some minimum wattage that triggers the new 4-wire code? I've seen some cooktops with 5 burners that use the 4-wire, but many of the 4 burner cooktops have a 3-wire.

If the 4-wire is truly safer, why not add one more piece of wire to the lower wattage cooktops? It seems like even the four burner cooktops could pack a whollap if they grounded through me rather than the copper wire. Doesn't make much sense, or am I missing something? Is it that the industry is that sensitive to the cost of 30" of copper? For our sake I hope not. Thanks for your thoughts.

-- Bill
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Old 04-14-2008, 11:59 PM   #10
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3 wire to 4 wire question


Most likely the new cooktop is 240 volts only the Jenn Air was 120/240 volts and required a neutral wire. Both are grounded circuits and equally safe by todays standards.

For cooktops:

3 wires = 240 volts 2 hots and ground

4 wires = 120 and 240 volts required 2 hots, a neutral (for the 120) and ground.

Last edited by Stubbie; 04-15-2008 at 12:13 AM.
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Old 04-15-2008, 12:40 AM   #11
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3 wire to 4 wire question


Thanks for such a quick reply. Now it makes more sense to me. I suspect that since my cooktop has regular manually operated controls rather than something like the touch sensitive controls, it doesn't need the 120.

-- Bill
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Old 04-26-2008, 04:14 PM   #12
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3 wire to 4 wire question


Hi,

I didn't have a chance to entirely uninstall my old cooktop and remove all the wiring from the box. I did today and discovered that rather than like the original poster, I only have 2 hots, and 1 white come from the panel.

However, I believe that the wiring in the entire house is run in metal conduit. Once I had the old cooktop removed, I turned the circuit back on and metered from each of the hot wires to the metal box. I got 120V on each one.

Would I be safe in attaching the ground from the new cooktop to the metal box, cap off the white from the panel, and attach the hots to the hots from the panel? Or do I need to fish a ground from the panel to the outlet? But, I don't find any grounds at all in the panel, so I'm not sure what I would attach it to. This is a house that was built in 1960, so maybe that was the standard then?

Thanks for any help you can provide.

-- Bill
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Old 04-26-2008, 06:57 PM   #13
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3 wire to 4 wire question


Your metal conduit is an acceptable ground. Connect the ground from the cooktop securely to the box. Wirenut the white and connect your hot wires. You will be all set.
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Old 04-26-2008, 10:06 PM   #14
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3 wire to 4 wire question


Quote:
Originally Posted by Andy in ATL View Post
As Stubbie said... It's simple once we have more info.
Nice to see you back, Andy!
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Old 04-27-2008, 12:33 PM   #15
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Thanks a lot jrclen. I've changed out switches, fixtures, and even added new circuits with no problems. Situations like this though, tell me how little I really know about electricity.

-- Bill

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