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Old 11-11-2012, 03:41 PM   #1
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wiring a new electric cooktop


My electric cooktop has three wires (black, red and bare). My junction box has four (black, red, white and bare). I first wired black to black, red to red and bare to bare, I capped the white wire in the junction box. The cooktop did not work. I then connected the white wire to the two bare wires, the cooktop now works. My question, is this correct or will it cause a problem?

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Old 11-11-2012, 04:30 PM   #2
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wiring a new electric cooktop


Sounds like your ground is bad, and the cooktop requires a neutral.

Can you post the make/model of that unit?

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Old 11-12-2012, 01:04 AM   #3
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Is this cooktop new and UL listed? It seems to be using the grounding conductor as the neutral return for 120V control circuitry. This is not allowed, and hasn't been for over a decade. You also have a bad ground, which is a problem.
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Old 11-12-2012, 01:45 AM   #4
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The cooktop is a new Bosch, model# NEM3664UC. For this model the power supply is 240 AC, 60Hz, 40 Amp. My old cooktop had four wires, which matched the ones in the junction box.

Are you saying that my ground could be bad on the cooktop? or are you talking about a bad ground on my home electrical system.
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Old 11-12-2012, 02:26 AM   #5
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240/208 spec on this model
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Old 11-12-2012, 11:17 AM   #6
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The cooktop is a new Bosch, model# NEM3664UC. For this model the power supply is 240 AC, 60Hz, 40 Amp. My old cooktop had four wires, which matched the ones in the junction box.

Are you saying that my ground could be bad on the cooktop? or are you talking about a bad ground on my home electrical system.
The ground wire from the cooktop junction box back to the panel is bad. However, it is very odd that this new cooktop doesn't function without that connection (not that you should use it ungrounded - but it should work!) since it has not been allowable to use a grounding conductor to carry control circuit current for quite some time.
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Old 11-12-2012, 01:47 PM   #7
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since this is just a cook top a neutral is probably not required...(like an ac unit) check the spec sheet.....check your wire awg as well
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Old 11-13-2012, 10:51 AM   #8
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since this is just a cook top a neutral is probably not required...(like an ac unit) check the spec sheet.....check your wire awg as well
His original post was complaining that the cooktop didn't work unless he connected the cooktop's grounding conductor to the home's neutral conductor. Connecting it to the home's grounding conductor didn't work. This is the whole essence of the problem here. It shouldn't require that connection to function properly. If it does, that means two things: his grounding conductor is bad, and the cooktop is using the ground as a neutral for it's control circuitry. Unless you can come up with a different explanation.
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Old 11-13-2012, 02:43 PM   #9
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wiring a new electric cooktop


Something is very screwy here and it oddly seems like there is a problem with the cooktop and your wiring. I found the installation instructions and the cooktop takes a normal L1, L2 208/240 with equipment ground, no neutral.

Do you have a voltmeter to check your junction box?

Last edited by zappa; 11-13-2012 at 02:45 PM.
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Old 11-13-2012, 04:42 PM   #10
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His original post was complaining that the cooktop didn't work unless he connected the cooktop's grounding conductor to the home's neutral conductor. Connecting it to the home's grounding conductor didn't work. This is the whole essence of the problem here. It shouldn't require that connection to function properly. If it does, that means two things: his grounding conductor is bad, and the cooktop is using the ground as a neutral for it's control circuitry. Unless you can come up with a different explanation.
...yes I know...there seemed to be a point of confusion as to the nuetral condutor.... BRA...do you know how to test for a bad ground?...or any broken line for that matter???
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Old 11-13-2012, 06:44 PM   #11
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No. I do not have a voltmeter, nor do I know how to test for a bad ground or broken line. Since the problem at this point is past my knowledge level, I am having a Bosch technician come out next next week to see if it is a cooktop problem. If not, then I will need an electrician to determine if my home wiring in correct (which I believe it is, after installing a Bosch double oven and dishwasher, I have never run into a problem like this). I will let you know the results.

Thanks for your help!
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Old 11-16-2012, 09:45 PM   #12
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...any news yet?
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Old 11-23-2012, 02:38 PM   #13
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My cooktop now works! The electrician determined that it was a loose ground wire connection in a junction box (box #1) next to my range hood. From box #1, the wiring travels to another junction box (box #2) for my electric cooktop. The loose ground wire connection was found in box #1.

The electrician quickly located the problem by looking at my electric panel and not seeing a ground wire from the switch that controls the cooktop. From there he concluded that there must be an intermediate junction box, between the panel and the cooktop. Fortunately, it was not in my attic, but in the cabinent next to the range hood.
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Old 11-23-2012, 04:26 PM   #14
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cool,,,happy cooking
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Old 11-23-2012, 04:55 PM   #15
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No. I do not have a voltmeter, nor do I know how to test for a bad ground or broken line. Since the problem at this point is past my knowledge level
I have a great deal of respect for you for admitting that. So many people injure themselves or put property and life at risk by not realizing when this occurs. Good for you!

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