2, 3, or 4 wires?

dwillisMarch 30, 2010

I just purchased a new whirlpool wall oven which has 4 wires (black, white, red, bare cooper)

The line coming from the wall has 3 wires (black, white, bare cooper)

The oven that I removed also had 4 wires (black, white, red, bare cooper) however I failed to note the configuration of the wires before I removed the old oven.

Before I install the new oven, can someone tell me which wires are connected to which?

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Billl

To make the oven "work", I'm sure they connected black to black, white from the wall to red from the oven, and bare from the wall to white and bare from the oven.

However, you should not do that. You should run a new 4 wire cable from the circuit box to the stove. Most older appliances that ran on 220v just required two hots and ground. Many new appliances with electronics etc are designed to use a neutral as well. While connecting the neutral and ground together will make the oven "work" it compromises your electrical systems most important safety feature - the ground.

    Bookmark   March 30, 2010 at 10:48AM
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petey_racer

Most older ranges were 120/240v and DID require a neutral. There was an exception in the code that allowed the neutral to be used also as the ground. This exception was removed several code cycles ago.

If the old oven had 4-wires then it DID require a neutral. Your old black white and bare feed did NOT have a neutral wire and was not ever correct.

Your new oven also requires a neutral so a new 4-wire circuit is mandatory in this case. Make sure you size it properly as well.

    Bookmark   March 31, 2010 at 9:23AM
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manchild

Petey, thats not exactly correct. There were quite a few ranges that were strictly 240v. They had mechanical timers and mechanical controls that did not need 120v. Therefore they only needed two hots and a ground making it quite possible that when this wire was originaly ran it was correct.

    Bookmark   March 31, 2010 at 5:06PM
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petey_racer

Manchild, re-read the original post. Here is the important part:
"The oven that I removed also had 4 wires (black, white, red, bare cooper) "
This is a 120/240v appliance.
The original 240v supply was not correct.
The only was it would have been correct is if it was SEU cable, and SEU does not fit the "black, white, bare CU" description.

Of course there are and were straight 240v appliances. It's just pretty much every free standing range I have ever seen has been 120/240v. Some ovens and cooktops I have seen have been straight 240v, but not many.

    Bookmark   March 31, 2010 at 6:23PM
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pharkus

And, I've said this before, but since it comes up again... even with electronic controls, straight 240V input is possible (and not any more difficult or expensive - the manufacturer just uses a slightly different transformer to obtain logic voltages). I fail to understand why we're keeping this stupid 120/240 thing around.

Same with clothes dryers. They do make 240V motors!

    Bookmark   March 31, 2010 at 10:23PM
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Billl

Just so the OP doesn't lose the forest through the trees.....

The bottom line is that if you have a stove with 4 wires, your outlet should have 4 wires. Whoever put in the last stove probably encountered the same dilemma you have. Their "fix" may or may not have been legal at the time, but it isn't considered the proper way to do it now.

You probably didn't plan on having to upgrade wiring, but you should just bite the bullet and do it right.

    Bookmark   April 1, 2010 at 9:53AM
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manchild

Bottom line the wire needs to be changed if you want to install that oven correctly.

Petey I'm not sure what you mean by not fitting the discription. If it was a straight 240v oven (which was a lot more common on older ovens) then what is wrong if they ran no neutral and a bare ground and two hot conductors? It was correct back then and certainly would be correct today.

    Bookmark   April 1, 2010 at 5:45PM
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manchild

Petey, to clarify I don't mean the old oven that is being replaced was installed correctly because that obviously wasn't. I'm talking about when the wire was originally installed it was to serve the purpose to feed only straight 240v ovens, which I'll say again was fairly common awhile back

    Bookmark   April 1, 2010 at 5:51PM
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spencer_electrician

I've found entire neighborhood subdivisions that were all wired with 10/2 with bare ground to dryers and 8/2 to ranges. It was illegal (for sure for the dryer) but as a lot things are, the inspectors did not notice. I think the detail of whether the grounded conductor was a neutral conductor or a grounding conductor often got overlooked. Or of course the scenarios of using straight 240 cooking equipment. Then again, all of these upscale houses/ condos had a modern version of a "kentucky 3-way" 3 way/ 4 way switch set up grabbing hot from one receptacle and neutral from a different receptacle (all wired with 14/2). Lots of major problems like that sly by when the inspectors just come in checking for staples and minimum outlet spacings. A lot of, not so good electricians probably figured that the 120/240 appliance only requiring 3 wires, meant they could run 2 conductor with ground, wrong of-course.

    Bookmark   April 1, 2010 at 5:55PM
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brickeyee

If the installation instructions for the new equipment allow a 3-wire installation just install the stove following those instructions.

While the type of cable may not be correct, it makes no difference in the installation.

    Bookmark   April 1, 2010 at 8:22PM
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petey_racer

Brick, if the new oven is 120/240v, which it is, then the existing cable is not correct, and yes, it matters.

    Bookmark   April 1, 2010 at 10:32PM
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pharkus

I'm anxiously awaiting the explanation of how the cable type makes any scientific/functional difference, or matters in any way beyond the exact wording of archaic and long-since-changed code.

    Bookmark   April 1, 2010 at 10:43PM
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spencer_electrician

An appliance using the grounding wire as a neutral would be a nasty surprise to an electrician moving bare grounds around in a panel. Remove it from the ground bar and have an energized bare wire in your hand. Also look at it as what if someone decided to change from 10/2 with ground to 1/2" EMT with 2 #10's using the pipe as ground? The pipe itself would be carrying the neutral current. I like to think of the act of using the bare wire in romex for carrying current is the same as the pipe scenario. Of-course it is unlikely anyone would do the scenario I described. The bare wire is just not made to carry current normally. Service cable is a different story.

    Bookmark   April 1, 2010 at 10:46PM
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petey_racer

Thank you Spencer. Good post.

So Pharkus, without a scientific explanation of why a bare ground in NM cable as a current carrying neutral is wrong, you'd have no problem leaving that wire in there and using it? Even though it is 100% wrong, and a very obvious and serious code violation??

    Bookmark   April 2, 2010 at 7:18AM
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brickeyee

"if the new oven is 120/240v, which it is, then the existing cable is not correct, and yes, it matters."

If the new oven is a 120/240 V load it will not have 3-wire installation instructions.

If you follow the instructions supplied with the unit you will install it correctly.

    Bookmark   April 2, 2010 at 8:46AM
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pharkus

So Pharkus, without a scientific explanation of why a bare ground in NM cable as a current carrying neutral is wrong, you'd have no problem leaving that wire in there and using it? Even though it is 100% wrong, and a very obvious and serious code violation??

I didn't say that.

Yes, it is illegal. Would I do it? Probably not. Would I plug a new appliance into an outlet that was already wired that way? Probably.

Your prior post implied that there may be some scientific/functional reason, beyond "code says so", and I'm quite inquisitive to know this reason. Let's not try to avoid my question (what is the reason?) by questioning my practice instead. I want to learn just as much as anyone else does here, and if there's something about electrical theory I don't know yet, I implore you to inform me.

    Bookmark   April 2, 2010 at 4:37PM
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brickeyee

"Your prior post implied that there may be some scientific/functional reason, beyond "code says so", and I'm quite inquisitive to know this reason. "

The only protection for the bare ground is the cable jacket.

It is not rated as an electrical insulator, and may even have been damaged during routine installation (especially if fished) leaving an exposed current carrying conductor.

I would be inclined to refuse to install the equipment for liability reasons (insurance companies like to find someone else to pay).

    Bookmark   April 3, 2010 at 11:56AM
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pharkus

It is not rated as an electrical insulator, and may even have been damaged during routine installation (especially if fished) leaving an exposed current carrying conductor.

Wow, I never even thought of that. Good point. Thank you.

I would be inclined to refuse to install the equipment for liability reasons

I definitely wouldn't hardwire something like that... but I have to be honest, if the appliance was cord-and-plug connected, and came with instructions for 3-wire connection (some 120/240 appliances still do), I probably would never be inclined to tear the receptacle apart to find out what kind of cable was used.

    Bookmark   April 3, 2010 at 8:33PM
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Decker1

I had lots of fun reading the squabble on here. I have installed about 5 wall ovens and have found no problem when I have just three wires going to the four from the new oven. I just put the white (oven) with neutral (wall) and red (oven) with white (wall), never a problem.

    Bookmark   March 30, 2013 at 3:20PM
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brickeyee

I have not seen an oven that did NOT come with the 3 wire option.

Most do not come with a cord at all.

It is up to the installer to provide a cord and wire it according to the installation instructions.

I am sure there are lots of illegal installations with the wrong type of cable feeding the stove receptacle.

It is not all that much of a risk though, since SE cable WAS allowed for 3-wire stove connections, and it has a bare ground just like NM.

    Bookmark   March 30, 2013 at 3:53PM
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petey_racer

"I had lots of fun reading the squabble on here. I have installed about 5 wall ovens and have found no problem when I have just three wires going to the four from the new oven. I just put the white (oven) with neutral (wall) and red (oven) with white (wall), never a problem."

Just because you have done a few illegal oven installs that work DOES NOT make it right. The bare wire in NM is NOT the same as the bare conductor in SEU cable.
And it's sad how you think potentially unsafe installations are funny, especially when some of them were done by you.

WHY do you think they changed the code many years ago???

Brick, SEU does NOT have a bare ground just like NM. The bare conductor in SEU cable is a concentric neutral.
This is why 3-wire range and dryer circuits MUST originate in the main panel. The bare wire is a NEUTRAL, not a ground.

    Bookmark   March 30, 2013 at 9:10PM
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bus_driver

This clown Decker1 (My Page) registers today and dredges up a thread that is 3 years old to tell us about the 5 ovens he installed.

    Bookmark   March 30, 2013 at 10:02PM
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Ron Natalie

It's kind of oddly worded in the code, but it is amplified in the handbook text, the requirement that the 3-wire range circuit terminate in the service equipment applies only the use of SE cable. As noted, using the bare NM ground is right out.

    Bookmark   March 31, 2013 at 11:46AM
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brickeyee

"SEU does NOT have a bare ground just like NM. The bare conductor in SEU cable is a concentric neutral. "

And that is mostly to allow it t\some function as armor.

Other than that, it is a bare neutral with nothing but jacket for protection.

The fact is is concentric has little to no impact on its electrical performance.

    Bookmark   March 31, 2013 at 4:09PM
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Ron Natalie

Type SE Style U may have a concentric neutral, but not all SE does an the code for this exception treats them all the same.

    Bookmark   April 1, 2013 at 9:17AM
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