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Old November 2nd, 2002, 07:30 AM
Anonymous Anonymous is offline
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Default Wiring new Jenn-Air Cooktop...too many wires!

Hi - I'm replacing an old (1980) Thermador electric cooktop with a new Jenn-Air model (it is 240v - I assume, but didnt check, that the Thermador was also 240 since it was a 5-burner radiant cooktop). I have pulled out the old Thermador and disconnected the electrical wiring from the unit (it was hard wired into the unit).

The wiring from the wall is in flexible metal conduit, and has a black, red, and bare copper. The wiring to the Jenn-Air is also in flex metal conduit, but has a black, red, white, and bare copper. You can see my confusion

In the Jenn-Air manual, it says "The neutral of this unit is grounded to the frame through the solid copper grounding wire. If used on new branch-circuit installations (1996 NEC), mobile home, rec vehicles, or in an area where local codes prohibit grounding through the neutral connector, untwist or disconnect the solid copper wire and connect the ground wire to ground in accordance with local coe. Connect the white neutral to the service neutral. Connecet all wires to the branch circuit with approved connectors..."

SO - my question is: what wires go where? I read on another post that i should never connect the white wires to bare ground wires - so where does the mystery fourth wire from the Jenn-Air cooktop go?

Thanks in advance!
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Old November 2nd, 2002, 10:53 AM
imported_Ron imported_Ron is offline
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You are absolutely on the right track regarding the manufacturers literature.
Since you have an existing oven circuit, as you've decribed, you may fall within the exception permitted in the electric code regarding this type of existing circuit. Only in this type of existing case, the branch circuit from the wall has one conductor for neutral and ground if the jacket is of a specific type.
Only an SE cable that has SE or service entrance cable written on the side of that cable can be used as existing using the bare as a neutral and a grounding conductor as a dual porpuse conductor.
I'm nervous since you said the circuit from the wall is flex metal. Double check if it is SE cable in the wall, or a nearby junction box. If it is, then you're good to go with connecting red to red, black to black and bare to the combined bare/white from the oven.
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Old November 2nd, 2002, 11:26 AM
Stefanw Stefanw is offline
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This was super helpful - thanks. I checked the wire coming from the wall - its really just three conductors in what looks to be a BX sleeve. The BX sleeve connects to a wall plate with a connector that can rotate (similar to the connector on the cooktop). Behind the wall plate there is a junction box into which a big cable with four wires (three sheathed and one bundle of twisted bare wires). The sheathed wires are joined to the red, black, and bare ground wires that i previously saw coming out of the wall. The bare bundle of wires is not connected to anything at this time.

Is it possible that I need to connect the white wire from the stove to the wire coming out of the wall that is currently joined to the bare ground coming out of the junction box? Then, connect the bare ground from the stove to the big bare bundle in the junction box that currently is connected to nothing?

Thanks again!
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Old November 2nd, 2002, 11:57 AM
Stefanw Stefanw is offline
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You know - i think I just figured it out. The BX-cable looking thing from the wall was probably part of the old Thermador cooktop - it connected into the junction box that contained the four wires - altho it only was connected to the three referenced in my above post.

The four wires are in the junction box are:
2 - black no markings
1- black with white stripe (im guessing this is neutral)
1 - braided bare wire

So i think i just need to connect the new Jennair metal conduit cable to the junction box and connect:

White/Black with white stripe
Bare/Bare braided wire

Sound right? Thanks!
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Old November 2nd, 2002, 03:38 PM
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Wgoodrich Wgoodrich is offline
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You are absolutely correct.

However I have a concern or two. First it is common that in the old days people did not know what to do with that bare wire. Take a voltage tester and test with the two black wires energized. Test to see if you have 120 volts between either black wire testing to that white wire. Then test to see if you have 120 volts between either black wire and that bare wire. If you do the go for broke with black to black and red to second black and white to white and green or bare to bare.

If you do not read 120 volts from those black wires testing to the white and testing to the bare then you have a wire not connected somewhere in this branch circuit. My concern is that you found the bare wire not connected in that box. Is that bare wire not connected somewhere else in that branch circuit like inside the panel where the breaker is? You may have to connect that bare wire at both ends of that branch circuit wire to use it. Just make sure they connected the other end of that bare wire in that panel, they might not have done that.

If you have all four wires in that branch circuit working then by all means connect that cook tops as you plan.

Now if you do use that four wire cable which you should if all four wires are working then you must separate that white and bare wire both where you connect to the wall and also inside the cook top where that cable enters and connects inside your cooktop. Look to see if they installed a metal or green jumper between the center screw of the terminal block inside that cook top and jumped that center silver screw to connect it to the metal frame of that cook top. If you find a jumper connecting the metal frame of that cook top to the silver center screw of the terminal block inside your cook top then remove it.

Let us know what you find

Good Luck

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