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Range died (maybe) and I bought a new one. It's on a 40A breaker, so I just assumed it was a 40A outlet. The only question they asked me for installation was "3-prong or 4-prong?", not anything else about the outlet. Looks like the new range (GE CHS900P2MS1) needs 40A. I told them I have 3-prong.

But I unplugged the old one and the receptacle says 30A. I pulled it out to check the wires and there appears to be a bare wire into the box. (I haven't yet tested if it's really ground, but I'm hoping it is). Since it'll be a few days before delivery, I have the opportunity to swap out the receptacle if useful.

I'm confused if my old range was on a 30A socket and the new range requires 40A, but no one asked any questions about that yet.

Assuming that's ground in there, what receptacle do I want to have?

enter image description here enter image description here Conductor photo closer photo of box

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  • 1
    Can you get us a better look into the back of the box please? Commented Apr 30, 2023 at 4:14
  • That isn't ground. 3-prong range and dryer ranges lack ground, and they're even more dangerous than that sounds. Commented Apr 30, 2023 at 4:37
  • What is the bare wire in the cable?
    – BowlOfRed
    Commented Apr 30, 2023 at 4:38
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    That would be a rather strong frame challenge. I don't want a gas stove.
    – BowlOfRed
    Commented Apr 30, 2023 at 5:02
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    @Harper-ReinstateMonica That is very clearly a ground wire in the box. So the incoming cable has ground and a 4-wire conversion (or hardwired with ground) is easy. Commented Apr 30, 2023 at 15:12

2 Answers 2

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There are three separate issues here:

3-wire vs. 4-wire

In the old days, ranges (and clothes dryers) were connected with three wires: hot, hot, neutral. Then ground wires came along and things were, in general, switched to four wires: hot, hot, neutral, ground.

There is a long history behind it, but eventually (1996 is a key date) 3-wire connections were banned, but technically old 3-wire connections are still allowed as long as nothing else is changed. What should happen is that as people replace there ranges (and clothes dryers) they should upgrade from 3-wire to 4-wire. But it rarely happens, because the appliances don't come with a cord attached and the dealers can just as easily attach a 3-wire cord/plug as a 4-wire cord/plug. So 27 years later, they're still selling 3-wire cords/plugs.

In some older houses it truly is hard to add that "missing" ground wire. But you have that wire, as should anyone with a house from 1996 or newer (and a lot of older ones as well). So that really answers that - 4 wire. Which means replacing the receptacle (not a big deal). But wait, there's more...

30A vs. 40A vs. 50A

30A uses one type of receptacle (10-30 for the old 3-wire, 14-30 for the new 4-wire). 40A and 50A use a different type of receptacle (10-50 vs. 14-50).

But in addition to the breaker and receptacle matching, the breaker and the wires need to match. The minimum size for 30A is 10 AWG, so it is a pretty safe bet you have at least 10 AWG wires. But the minimum size for 40A is 8 AWG. You can use 8 AWG on a 30A circuit, but you can't use 10 AWG on a 40A circuit.

So you need to figure out what size your wires are. There are a number of different possibilities for your existing 40A breaker, including:

  • 10 AWG wire, 30A range - not suitable for your new 40A range
  • 10 AWG wire, 40A range - not suitable for your new 40A range and wasn't suitable for your old one either!
  • 8 AWG wire, 30A range - replace the receptacle with a 14-50 and get a matching 4-wire cord/plug. Your old range had a larger breaker than it should have, but not a big deal.
  • 8 AWG wire, 40A range - replace the receptacle with a 14-50 and get a matching 4-wire cord/plug. Your old range had the wrong cord/plug/receptacle, which could have caused problems, but you'll be fine with the new range.

So the first step is to determine what size wire you have. If it is 8 AWG then replace the receptacle, etc. and you're all set. If it is 10 AWG then you need to replace the wires, which could be anything from a small task yo a huge ordeal.

Hardwired vs plug/receptacle

I generally recommend hardwired connections for ovens/ranges. Most can be installed hardwired on plug/receptacle. The wire size/breaker/etc. issues are identical, but with hardwired connections there is simply no receptacle in the middle of it all.

The instructions for your range included hardwired connection as well as cord/plug connections. They call it "conduit", but it doesn't matter whether you have conduit in your house or not, as you will in any case just use a short flexible conduit from the existing receptacle box (but without a receptacle - i.e., add a cover with a place to connect the conduit) to the range.

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  • Outer diameter of the insulation appears to be very close to .25inch. That seems to be 6. I can't imagine why that would be run, but seems very unlikely that it's 10.
    – BowlOfRed
    Commented Apr 30, 2023 at 4:00
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    The way to tell for sure is to measure the wire, not the insulation, or find printing on the wire. But if the wires are in a cable (common in most places outside New York and Chicago) then the printing is often only on the cable sheath, which is not accessible from inside the box. Depending on your breaker panel location, you may be able to get to the cable sheath easily there. Or not. Depends. Commented Apr 30, 2023 at 4:02
  • Added a photo. Sheath is cut so only a scrap is in the box. No markings on the individual wires that I see. Conductor is not much smaller than .25inch (added photo). Looks like whoever cut the insulation nicked the conductors. Not a huge amount of slack in the box, but maybe I can trim it back more properly.
    – BowlOfRed
    Commented Apr 30, 2023 at 4:33
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    It's likely cable, since it has a bare ground wire. So wouldn't it being stranded indicate that it's at least 8 AWG? IDK that I've ever seen 10 AWG and smaller stranded in a cable format, only 8 and larger.
    – Huesmann
    Commented May 2, 2023 at 14:11
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    @Huesmann Correct. I didn't notice the strands originally. Commented May 2, 2023 at 14:12
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3-wire connections are dangerous. If the neutral comes loose, it guarantees the chassis of the equipment will be energized, due to the bonding strap on the equipment tying chassis to neutral.

Replace that with a 4-wire socket and Bob's your uncle

Go ahead and wire the 2 hots and neutral to the new 4-wire socket. Do not touch ground. Use a torque screwdriver.

When converting the range cord to 4-prong, follow the instructions, because they will show you how to disconnect (isolate) neutral from chassis.

Wait... NOT wire ground???

Yes. Code requires with metal boxes, ground go to the metal box first. Once that's done, when you bolt the receptacle to the box, it will pick up ground via hard/flush metal on metal contact between box flange and receptacle yoke (frame). This requires the yoke bottom out, and not be floating above the box on drywall ears.*

* Ignore this sentence if the receptacle is marked "Self-Grounding", that means it has a wiper to pick up ground off the mounting screws.

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