Replacing 50-amp cooktop receptacle

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Old 07-12-11, 08:36 PM
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Replacing 50-amp cooktop receptacle

I am changing my 50-amp 3-wire receptacle used for my old cooktop to a junction box (still the 3-wire) to hardwire my new cooktop (which the cooktop allows).
The question is the existing receptacle circuit has 2 blacks and a white wire instead of black, red and white.
Of course the wires from the new cooktop say connect the black from the cooktop to black in the junction box and the red from the cooktop to the red in the junction box.
Am I correct that the two blacks on the receptacle are the same as if they used one black and one red. And therefore I can connect either black to the black from the cooktop and the other black to the red from the cooktop?
Is that correct?
I know changing to 4-wire is best, but given the location of the island where the cooktop is going running new wire would be near impossible.
Could you please tell me if my assumptions are correct?
Thank you.
 
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Old 07-12-11, 09:20 PM
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If this is metal conduit continuous to the breaker box you may be able to install a 4 wire plug. However if the cook top is 240v not 120/240v you don't need a 4-wire receptacle.
 
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Old 07-12-11, 09:35 PM
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The cooktop is 240v and not the 120/240v.
So then sticking with 3-wire am I good with the 2 blacks and 1 white instead of 1 black, 1 red and 1 white and then connecting either black to the red from cooktop and the other black to black from cooktop?
Thank you.
 
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Old 07-12-11, 09:42 PM
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Blacks can be used for the hots. However you need a ground. Do you have metal conduit? If it is metal conduit you are good but if you don't by current code if the white is #6 or smaller it can't be used as ground however you may be grandfathered. Wait for the pros to weigh in on this.
 
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Old 07-12-11, 10:25 PM
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I do have metal conduit and from the reply to a question I posed previously in a different thread I would be grandfathered on the 3-wire. Plus the cooktop instructions allow hookup to 3-wire.
So then sticking with 3-wire and the fact that I have 2 blacks and 1 white instead of 1 black, 1 red and 1 white, then would I be good connecting either black to the red from cooktop and the other black to black from cooktop?
Thank you.
 
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Old 07-12-11, 11:12 PM
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The cooktop is 240v and not the 120/240.... I do have metal conduit
Blacks to red and black. It doesn't matter which to which.
White capped with a wire nut. It is not used on a 240v only hook up.
Ground to the metal box using an approved ground screw.

I would be grandfathered on the 3-wire
Because of the conduit you could if needed connect a 4-wire receptacle so no grandfathering needed so long as the Jbox is metal and conduit continuous.
 
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Old 07-13-11, 10:52 AM
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Black and red are interchangeable on a cooktop so it doesn't matter which goes to which black. Should be no problem to proceed with the cooktop hookup on the three-wire circuit per mfr. instructions.

The only thing you need to watch for would be if the old wires are aluminum. They cannot be connected to the cooktop's copper wires without special connectors. If the existing wires are copper you can splice them directly to the new cooktop wires using the big blue size wirenut. If the old wire looks silvery like aluminum use a sharp blade to scrape it as sometimes it is copper with a tin coating.
 
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Old 07-13-11, 02:40 PM
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If aluminum, use a polaris rated for aluminum.
 
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Old 07-13-11, 06:10 PM
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At how many amps is your new cooktop to be protected? I seriously doubt you need a full 50 amps for a cooktop. You may need to change the breaker in your panel to a 30 or 40 amp breaker.
 
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Old 07-13-11, 06:16 PM
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Originally Posted by Justin Smith View Post
If aluminum, use a polaris rated for aluminum.
They are rated for both aluminum and copper.


IPL Series One Side Wire Entry

IPL Series connectors are insulated with high-dielectric strength plastisol. Molded for precise fit and supplied with removable access plugs over the hex screws. Wire entry ports on one side only. Eliminates the need for cover and taping. Abrasion and chemical resistant. UV rated. Will not support combustion. Cold temperature rated to -45C. Dual rated for use with copper and/or aluminum cables. Rated 600 V, 90C. Not recommended for fine-stranded, flexible wire. To receive the material in bags, add -B to the part number.
NSi Industries - One Side Wire Entry
 
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Old 07-13-11, 08:21 PM
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They are rated for both aluminum and copper.
I was just making sure there wasnt one not rated for aluminum. I know all of the ones ive seen are.
 
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Old 07-13-11, 09:08 PM
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Ben,
Great. Thanks very much for that clear explanation.
I checked and my wires are copper so I am good to go.
Thanks again.

-Scott
 
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Old 07-13-11, 09:54 PM
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The new cooktop is 40A and the breaker is 50A.
However the old cooktop put in when the house was built 20 years ago is rated at 35 amps on this 50A circuit. So I assume this is not a code issue since that must have passed code.
Do you guys think I am okay leaving the 50A breaker?
 
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Old 07-14-11, 10:05 AM
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Nope, change it to a 40A; most panels this is about $10. The old one was the wrong size.
 
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Old 07-14-11, 08:10 PM
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Okay. Thanks for all the help.
 
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