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Is it okay to switch my range 3 prong outlet to a 4-prong outlet 50 amp as long as there is a ground wire in the 3-prong wiring? Instead of switching the plug to a 3 prong. new range has a 4-prong plug. Another question is currently the 3-prong outlet is just lying on the ground. Would be better to mount to the wall? Currently I have a 40-amp breaker and the new range will have 40-amp requirements.

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    Can you post a picture of the wiring for the outlet. Are you sure it is ground and not a bare neutral? On a three prong outlet for a stove the third wire is usually neutral, you want four wires.
    – crip659
    Aug 22, 2023 at 21:48
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    This may shed some light (yup it's a dryer. The basic ideas hold true, though.): diy.stackexchange.com/q/279386/18078
    – Ecnerwal
    Aug 22, 2023 at 23:03
  • Have you determined whether you have both an insulated neutral and a bare or green ground in your house cable? There will of course be two hots so four wires total. Aug 23, 2023 at 19:37
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    Jim, i have not taken apart my receptacle yet. When I do I hope there will be four wires. So i can go the safer route with a 4-prong receptacle. And I will also check to see if the wiring is copper or aluminum. Aug 23, 2023 at 22:25

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The 4-prong outlet is a big safety upgrade. All ungrounded appliances were banned in 1965, but dryers/ranges got a variance on demand of the manufacturers, claiming "grounding" to the neutral fine is safe. Subsequent experience showed it was killing quite a few people, because a loose neutral creates a "hot skin" condition. We get reports of that here several times a year. As such, these were banned in NEC 1996.

Still, builders or sellers often illegally downgrade a dryer or range outlet at request of a customer who has a pre-existing 3-wire dryer or range. (it's the builder's bailiwick to change a house socket, not an appliance cord).

If you have the ground wire available, I recommend upgrading the box. They make surface-mount boxes, and fun fact, if you look closely at the box, it has a particular "design language" - Leviton's extremely boxy shape, P&S's rounded corner with bottom bevel, or the Eaton Cooper round top with side bevel. If you make a point to get the same style, the old back plate might fit your new socket, in which case less work!

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If the wire is there and goes all the way back to your box, feel free to swap out for the modern 14-50 outlet. I did exactly the same thing at my last house when replacing the range, as I found out the previous owner had installed 6/3 wire but a 3-prong outlet. It wasn't the only electrical mistake they made.

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    Quite a few NEMA 10 circuits still out there. Some do not have ground available. Some also have a bare wire used for neutral, which can be mistaken for a ground wire. Hopefully OP has your problem instead.
    – crip659
    Aug 22, 2023 at 22:08
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From your question I understand that the electrical wiring from the house serving the range just comes out of the wall and goes into a (metal?) electrical box in which there is a "3-slot" receptacle. Is this right? If so, you do not have to go to the trouble and expense of fitting that into the wall. If you want to use a 4-slot receptacle (NEMA 14-50), you could just install that receptacle in the box at the end of the cable and have it lie on the floor behind the stove.

Alternatively you could not bother with a NEMA 14-50 receptacle and "hard wire" the cord from the stove to the house wire. To do that you would get a 50 A appliance whip. You could just cut the plug off the cord you have but I would hate to mutilate the cord in case you would later want to use it to plug into a NEMA 14-50 receptacle. This hard wired connection would be inside the box currently at the end of the house wire.

Evidently the old range had a 3-prong plug which plugged into this "3-slot" receptacle. Is that right? If so, turn off the breaker to this circuit, take the cover off the box and find out how many wires are in the house wiring to this circuit--there will be either 3 or 4. You also need to determine what size they are, and whether copper or aluminum. What are the colors of the insulation on the insulated wires?

EDIT

My 30+ year old GE range with cooktop and oven AFIK requires 240 V and 120 V so it needs a 4-wire cable (L1, L2, N, Gnd). Do more modern ranges only require 3-wire (L1, L2, Gnd)? You state that your range is fitted with a 4-wire cord and plug (which would be a NEMA 14-50p). I suppose this means your range requires both 240 V and 120 V.

You need to find out how many wires are in the house cable by looking in the box where the 3-wire receptacle is currently installed. If you do this, please report this information here so people can advise you how to proceed.

Also, report whether the conductor in the house wiring cable is copper or aluminum. If it is aluminum, and you want to install a NEMA14-50 receptacle, then you will have to get a receptacle which is approved for aluminum. Some NEMA 14-50r are copper only. It may be easier and cheaper to just hard wire aluminum to a copper cord or appliance whip using Polaris connectors which are approved for copper and aluminum.

I wish I had done that instead of converting my original hardwired connection to a NEMA 14-50R in the wall. The particular 14-50R I bought is labeled for Cu or Al, but it simply did not make as good a connection to the stranded aluminum conductor as I would like or feel comfortable with.

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    One cool thing about hard-wiring: if the appliance supports it, a 3-wire connection with two hots and a ground may be a perfectly safe way to use an existing 3-conductor cable or even a new three-wire circuit. I did exactly this for an install of a new cooktop recently. There's conduit, so if we ever need the fourth conductor it's no big deal. For now, though, two hots and a ground hardwired to the cooktop works perfectly.
    – KMJ
    Aug 23, 2023 at 17:05
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    In response to your edit: yup, some modern ranges have all 240v electronics. Now that switching power supplies are common the cost to make them work off 240v is trivial compared to having them be 120v only, and they can save on internal wiring. Mostly you see it in ovens and cooktops though. As an example, if you have a 4-wire circuit when installing this cooktop, you cap the neutral wire off: images.thdstatic.com/catalog/pdfImages/28/…
    – KMJ
    Aug 23, 2023 at 22:11
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    3-wire might only be cooktops and some wall ovens. I flipped through the installation manuals for a half dozen ranges and only saw four-wire hard wired installs.
    – KMJ
    Aug 23, 2023 at 22:21

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