New 4 wire cooktop to 3 wire supply?

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  #1  
Old 05-31-19, 06:25 AM
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New 4 wire cooktop to 3 wire supply?

Ok, so I probably know the answer already about most likely needing a new wire set ran from the breaker box, but wanted to check first.

House was built in 1987. I am replacing an old Roper electric cooktop that had a black wire, red wire, and bare ground. The breaker is a double 40 amp.

The way it was hooked up prior
Black = Black
Red = White
Ground = Ground

The new cooktop has a red, black, white, and green,, here is the model number of the cooktop: GJC3655RB

In the info it states the below:
https://assets.ajmadison.com/ajmadis...86066-D-WH.pdf

"Electrical: A 4-wire or 3-wire, single phase, 240
volt, 60 Hz., AC only electrical supply is required
on a separate, 40-amp circuit, fused on both sides
of the line. Use 8 gauge copper wire."

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So I am wondering it doesn't mention 120/240, but just 240, does this mean I that I do or do not need any further wiring to hook this up? Also, in the diagram for the wiring, it shows red=red, blk=blk, but then it says white&green from cooktop to white(supply), one I don't have a red in the supply, two the white was hooked to red in the old setup...

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Last edited by PJmax; 05-31-19 at 10:50 AM. Reason: resize pictures
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  #2  
Old 05-31-19, 06:51 AM
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The white in your box was a hot. Call it red for sake of explanation. You therefore have red and black hot no neutral. A 240v only feed. The bare ground in NM-b can;t be used as a neutral. You need to run a new 3-conductor cable (H-H-N+G). 8-3
NMb will be okay.
 

Last edited by ray2047; 05-31-19 at 07:33 AM.
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Old 06-01-19, 04:46 AM
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You also need to add a connector to the flex coming from the oven. You can't just run the wires through the KO like that.
 
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Old 06-03-19, 06:38 AM
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Tolyn, I realize that, I hadn't put it on yet as I was checking the wires and then saw the issue.
 
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Old 06-03-19, 11:03 AM
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It does say 3-wire. I see the instructions at http://static.appliancesconnection.c...509b6e83e0.pdf which are same as your image. It says to "connect the green or bare and white cooktop cable wires to the white (neutral) wire." That's wrong in several ways.

Can you open up the cooktop to see what the white and green wires actually connect to?

Also try contacting Whirlpool for an explanation - Chat or Call 1 (800) 541-6390 for Countertop Appliances, Kitchenware & Kitchen Tools
 
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Old 06-03-19, 12:45 PM
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Remember the title is wrong. He has a 2 wire (conductor) feed not 3-wire.
 
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Old 06-03-19, 03:18 PM
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Good point about wire count. That is part of the confusion as the vendor's documentation includes the grounding wire in the count. They document 4-wire as H-H-N-G, 3-wire from supply as H-H-N, and 3-wire from the cooktop as H-H-G.
 
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