# wiring electric cooktop 4 wires to 3 wires



## 1234mom (Jun 30, 2011)

Have a new whirlpool G7CE3055 cooktop with 4 wires (black, red, white, bare) and 3 wire junction box (black, white, bare). Instruction say to wire black to black, Red to red, and cooktop white & bare to bare. The problems is that I don't have red at the junction box. what now?


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## AllanJ (Nov 24, 2007)

You may not wire it up at all until you run a new cable up from the panel with white neutral, red and black for 240 volt hot, and bare or green for ground.

Most likely the white and black feed wires in the box are 240 volt hots in y our situation. Ground (bare) may not be used as neutral.


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## Jim Port (Sep 21, 2007)

Your old unit must have been 240 volt only. The new unit has both 120 and 240 volt components.


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## 1234mom (Jun 30, 2011)

can the cooktop safely be wired with the black to black, white(junction box) to red(cooktop), and bare(junction box to white&bare(cooktop)?


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## 1234mom (Jun 30, 2011)

AllanJ said:


> You may not wire it up at all until you run a new cable up from the panel with white neutral, red and black for 240 volt hot, and bare or green for ground.
> 
> Most likely the white and black feed wires in the box are 240 volt hots in y our situation. Ground (bare) may not be used as neutral.


so what happens if it is wired black to black, white (junction box) to red (cooktop), bare (junction) to white & bare cooktop??


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## kbsparky (Sep 11, 2008)

Can you post a picture of the wires in your junction box?


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## 1234mom (Jun 30, 2011)

kbsparky said:


> Can you post a picture of the wires in your junction box?


 
Unfortunately, at the moment, I'm not able to do so. What are you wanting to see or are looking for?


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## rbj (Jun 24, 2011)

1234mom said:


> Have a new whirlpool G7CE3055 cooktop with 4 wires (black, red, white, bare) and 3 wire junction box (black, white, bare). Instruction say to wire black to black, Red to red, and cooktop white & bare to bare. The problems is that I don't have red at the junction box. what now?


I agree with Jim, the mfr is suggesting non-compliant wiring. What could happen? The cooktop surface becomes an non-grounding surface with lethal shock capabilities from other surrounding non-grounding appliances. (I.e. toaster without polarized hookup)


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## mpoulton (Jul 23, 2009)

1234mom said:


> can the cooktop safely be wired with the black to black, white(junction box) to red(cooktop), and bare(junction box to white&bare(cooktop)?


It will function normally, and be unsafe. That's a code violation for good reason. The bare ground wire would be carrying current during normal operation.


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## rbj (Jun 24, 2011)

what mpoulton said.


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## 1234mom (Jun 30, 2011)

do all new cooktops have 4 wires? the old unit had only 3 wires and thus was hooked up to the 3 wires from the junction box just fine. Why does this new unit now have 4 wires when it is just a newer version of the old one? And why does the mfg. instructions allow for connection to a 3 wire box? The problem, again, that I ran into and was confused about was the fact that I had no set of reds to connect? What do the colors of the wires mean? Finally, I'm in Alabama and how do I go about finding a licensed electrician that I can trust to run a new power supply from my breaker box?


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## 1234mom (Jun 30, 2011)

mpoulton said:


> It will function normally, and be unsafe. That's a code violation for good reason. The bare ground wire would be carrying current during normal operation.


 that doesn't sound good at all.


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## rbj (Jun 24, 2011)

1234mom said:


> that doesn't sound good at all.


Even more exciting...that cooktop metal surface can be carrying current to the wire also.


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## rbj (Jun 24, 2011)

1234mom said:


> do all new cooktops have 4 wires? the old unit had only 3 wires and thus was hooked up to the 3 wires from the junction box just fine. Why does this new unit now have 4 wires when it is just a newer version of the old one? And why does the mfg. instructions allow for connection to a 3 wire box? The problem, again, that I ran into and was confused about was the fact that I had no set of reds to connect? What do the colors of the wires mean? Finally, I'm in Alabama and how do I go about finding a licensed electrician that I can trust to run a new power supply from my breaker box?


In the old days blk-red-wht did not use an equipment grounding conductor (EGC) The neutral was used as the grounding bond. In cases where truck stock only had blk-wht-bare, (I.e. SE cable) was substituted for the same 240V circuit with the bare as a neutral.


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## mpoulton (Jul 23, 2009)

Depending on the specific cooktop, the previous version may not have required a neutral. Some do, some don't. In the olden days, a three wire connection with an INSULATED neutral was used for stoves and dryers. That old-fashioned connection did not have a ground, and the metal case of the appliance was connected to the insulated neutral instead. This posed a major problem if the neutral connection ever became loose - the metal appliance itself would be electrified. That's why this is no longer allowed for new installations. It was never permissible to use an uninsulated grounding conductor as a neutral, which your prior cooktop may have.


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## 1234mom (Jun 30, 2011)

So if the cooktop has 4 wires does that mean it has both a 120v and 240volt component? Would the white wire from the cooktop be the neutral and would that wire be the one that operates the light that indicates the surface is hot and/or in use?


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## frenchelectrican (Apr 12, 2006)

I will simplify with photos.,

10-2 NM 










8-2 SE cable










Let us know the diffrence there.

Merci,
Marc


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## 1234mom (Jun 30, 2011)

mpoulton said:


> Depending on the specific cooktop, the previous version may not have required a neutral. Some do, some don't. In the olden days, a three wire connection with an INSULATED neutral was used for stoves and dryers. That old-fashioned connection did not have a ground, and the metal case of the appliance was connected to the insulated neutral instead. This posed a major problem if the neutral connection ever became loose - the metal appliance itself would be electrified. That's why this is no longer allowed for new installations. It was never permissible to use an uninsulated grounding conductor as a neutral, which your prior cooktop may have.


So if wired the way I mentioned before, black to black, white from junction box to red from cooktop, and bare from junction box to white and bare from cooktop, how would if be unsafe? Would it be a fire hazard or an electrocusion? Is there a way with current wiring to connect it safely?


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## 1234mom (Jun 30, 2011)

mpoulton said:


> It will function normally, and be unsafe. That's a code violation for good reason. The bare ground wire would be carrying current during normal operation.


 
And if the bare ground wire is carrying a current during normal operation what happens?


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## Techy (Mar 16, 2011)

Shock hazard, using ground as a neutral conductor puts neutral current on grounded metal parts of the cooktop.


your 4 wire(hot hot neutral ground) cooktop cannot be safely connected to a 3 wire (hot hot ground) connection


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## 1234mom (Jun 30, 2011)

Techy said:


> Shock hazard, using ground as a neutral conductor puts neutral current on grounded metal parts of the cooktop.
> 
> 
> your 4 wire(hot hot neutral ground) cooktop cannot be safely connected to a 3 wire (hot hot ground) connection


Why do you think that the mfg. instructions actually give this as an option-connecting 4 wires to 3?


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## Techy (Mar 16, 2011)

because prior to the 1996(?) NEC it was allowed


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## 1234mom (Jun 30, 2011)

Techy said:


> because prior to the 1996(?) NEC it was allowed


so what is the likelyhood of getting shocked?


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## mpoulton (Jul 23, 2009)

Techy said:


> because prior to the 1996(?) NEC it was allowed


THIS installation was never allowed - a bare grounding conductor was never permitted to be used as a neutral. The formerly-common 3-wire connection used an insulated neutral, not bare.


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## mpoulton (Jul 23, 2009)

1234mom said:


> And if the bare ground wire is carrying a current during normal operation what happens?


If everything is perfectly intact, nothing happens. However, if a loose connection develops in the grounding connection anywhere between the appliance and the panel, then all of the bare metal parts of the appliance will be electrified. Depending on how the circuit is run, other random metal things in your house may also become electrified. That's not good.

To answer one of your earlier questions: yes, the cooktop has both 120 and 240v components internally. Usually the clock, timers, lights, etc. operate on 120V (from one hot to neutral), while the heating uses 240V. There's a trend for newer cooktops to use only 240V to avoid this problem altogether.


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## rbj (Jun 24, 2011)

mpoulton said:


> If everything is perfectly intact, nothing happens. However, if a loose connection develops in the grounding connection anywhere between the appliance and the panel, then all of the bare metal parts of the appliance will be electrified. Depending on how the circuit is run, other random metal things in your house may also become electrified. That's not good.


I think what mpoulton and I are saying (my earlier post about a flawed toaster) did not get understood. So nothing happens at the cooktop with a tight neutral until a nearby appliance that is not polarized (neutral prong-phase prong reversed) can cause a lethal shock from the perfectly intact 4 to 3 wire cooktop connection. Sure the appliance mfr is going to give a quick solution to keep the sale...but it is a flagrant code violation due to the hazard and unsafe potential.


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## brric (Mar 5, 2010)

mpoulton said:


> THIS installation was never allowed - a bare grounding conductor was never permitted to be used as a neutral. The formerly-common 3-wire connection used an insulated neutral, not bare.


This statement is not true. SE cable was used for years on ranges and the like. The OP can install the new cooktop to the old wiring as per the exceptions if the existing cable is SE and it is large enough to carry the load of the cooktop.


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## HouseHelper (Mar 20, 2007)

brric said:


> This statement is not true. SE cable was used for years on ranges and the like. The OP can install the new cooktop to the old wiring as per the exceptions if the existing cable is SE and it is large enough to carry the load of the cooktop.


But the OP stated the existing wires were black/white/bare... if it were SE, they would be black/black or black/red/bare. So It is NM and if the old unit required 120/240V, it never was wired correctly.

And FWIW, SE could only be used if the circuit originated at the service panel.


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## brric (Mar 5, 2010)

HouseHelper said:


> But the OP stated the existing wires were black/white/bare... if it were SE, they would be black/black or black/red/bare. So It is NM and if the old unit required 120/240V, it never was wired correctly.
> 
> And FWIW, SE could only be used if the circuit originated at the service panel.


You are correct.


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## 1234mom (Jun 30, 2011)

brric said:


> This statement is not true. SE cable was used for years on ranges and the like. The OP can install the new cooktop to the old wiring as per the exceptions if the existing cable is SE and it is large enough to carry the load of the cooktop.


How do I know if the existing cable is SE and large enough to carry the load? Like I said I have a Black, White, and bare in the junction box, what gets connected to what and what are the dangers?


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## rbj (Jun 24, 2011)

HouseHelper said:


> But the OP stated the existing wires were black/white/bare... if it were SE, they would be black/black or black/red/bare.


Depends....SE-U= bk/wh/bare ...SE-R= bk/rd/wh/bare


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## kbsparky (Sep 11, 2008)

I've never seen SE-U cable with black/white/bare. Most of them that were marked were black/red/bare.


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## kbsparky (Sep 11, 2008)

1234mom said:


> And if the bare ground wire is carrying a current during normal operation what happens?


Prior to the 1996 edition of the _Code_, dual-voltage (120/240) dryers, ranges, cooktops, wall ovens, etc. were permitted to be installed using 3-wire cable, without a grounding conductor.

There was an exception in the Code that permitted the use of type SE cable for these circuits (when originating from the service panel), where the "bare" conductor consisted of several small strands twisted together. That conductor acted as a neutral, even though it was bare. The appliance was permitted to be grounded thru the neutral, using a bonding strap connected to the appliance frame.

Your existing circuit appears to be regular type NM cable (commonly called "romex") which has a solid bare grounding conductor present. This circuit was most likely for 240 Volts use only, as evidenced by the pigtail to your old cooktop. That bare wire is there only for grounding purposes, and is not the same thing as a neutral conductor, which is current-carrying during normal operation of the appliance.

Is there an operational difference between a single solid bare conductor, and a multi-strand bare concentric conductor? Not really. 

The main difference here is one type of wire was permissible to be used as a current-carrying conductor, while the other is not. This is but one example of how the _Code_ is manipulated by manufacturers' and special interest lobbyists, implementing rules that may or may not be in the best interests of safety.


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## rbj (Jun 24, 2011)

kbsparky said:


> I've never seen SE-U cable with black/white/bare. Most of them that were marked were black/red/bare.


SE-U is Blk-Blk-bare Al(Southwire), maybe some earlier were fabricated with Blk-Rd-bare but in smaller Awg sizes under 1Awg. Depends on the mfr and when fabbed. Most old woven SE that I took out of older structures are Bk-Bk-bare copper.


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## kbsparky (Sep 11, 2008)

rbj said:


> ...but in smaller Awg sizes under 1Awg....


We are dealing with smaller sizes in this discussion. Most of the older stuff I have encountered had a red stripe on one of the conductors, but it was flaking off, due to its age .... :whistling2:


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