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I removed an electric cooktop and installed a gas one. The gas cooktop needed a 15 amp receptacle for the igniter. The electric cooktop was hardwired but had a double gang box.

I installed a 20amp 240 in the double gang then jumped 1 leg over for a 15amp/120 receptacle.

The house was built in the 60s and the wire is #6AL. To be code legal can I just pull the 30amp breaker and buy a 15amp double pole? Also is it code legal to have different voltages in a double gang box?

If not, can I just remove the 20amp/240 receptacle and put a wire nut on the leg I don’t need and pigtail a #12/14Cu to the 6AL?

I thought using the 20amp/240 receptacle would be more professional to utilize to switch to copper for the 120 receptacle than just twisting wires together, but I am selling the house and can’t find a faceplate for them.

6AL seems kinda heavy to stuff directly into a 120. What is the best way to accomplish it?

Another problem I found going to paint a room was a receptacle with black tape on the white wire and the black wire used as neutral and then jumped to a ground wire.

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  • Very confused. "AU" means Gold. I am sure you don't have gold wires. So it could be you meant AWG (the US wiring size), in which case 10 and 12 and 14 make sense. Or it could be you meant AL for Aluminum, in which case the reference to Copper makes sense. So please clarify: If AU = AWG, change to AWG. And do you have any aluminum wires? Also sounds like you have a 240V 30A receptacle currently, is that correct? If so, is it 3 wire or 4 wire? Or more specifically, what wires do you actually have? Because while 10 AWG is larger than needed for 20A it is OK. But depending on what wires you have Commented Feb 29 at 17:20
  • What is "#10AU"? Should "AU" be "AL" for "Aluminum"? What do you mean by "jumped 1 leg over for a 15amp/120 receptacle"? What jumped from what to where? If "AU" means "AL", then yes, #10 AL is the equivalent of #12 CU and is acceptable for a 20a circuit. Many receptacles can be had with CU/AL ready terminals, so you wouldn't even need to pig tail them.
    – FreeMan
    Commented Feb 29 at 17:21
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    there may be other concerns. A picture of the existing wires and receptacle would help. As far as faceplate, assuming it is a standard size box it is no problem getting faceplates - e.g., one side standard receptacles and the other side blank. Commented Feb 29 at 17:21
  • Sorry, I did mean AL not AU. It is a house in the USA, the original cooktop was a 3 wire hot/hot/neutral. It could be a number 8 or 10 I can’t remember and need to double check. I remember it wouldn’t fit a CU 15 amp receptacle, with out trimming the wire down. I used a 240/20amp receptacle to connect the AL wire, then daisy chained a 120 receptacle next to it with a piece of copper wire. Commented Feb 29 at 17:39
  • If it's Aluminum and was breakered 30A it had better be 8AWG. If you are putting 20A receptacles on it, it needs to be re-breakered at 20A. Do you have a ground wire here, or just two hots and a neutral? That's a most likely problem from that particular era. Edit in pictures of the opened box (breaker off, of course.) A NEMA 6-20 or 6-15 (240V, 20 or 15A) uses the same faceplates as a NEMA 5-20 or 5-15 (120V, 20 or 15A) so that part is not making sense with no picture.
    – Ecnerwal
    Commented Feb 29 at 17:45

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Likely issues (but we don't know yet) - you may not have a ground wire, if the electric stove supply wiring from the era when this was all the rage has only hot, hot, and neutral wires, with no 4th ground wire or a metallic conduit as a ground path.

Your aluminum wire should be 8 AWG if it was breakered at 30A. But it was actually 40A per the picture, so...

Your breaker must be changed to a 20A (or 15A, but 20A is fine if the 15A outlet is a duplex) so you are not supplying 40A to a 15/20A outlet (whether 240V or 120V)

120V and 240V in the same box is fine. Your main panel is one example of such a box. If devices are on the same yoke (120V/240V outlets like that are made) the breakers must be handle-tied (so if being fed from the same dual-pole breaker as described, you'd be set.) If devices are on different yokes the breakers don't need to be tied, but a clear label of the applicable breakers is highly reccomended.

120/240V outlets sharing a yoke

Top is 120V-20A bottom is 240V-20A Image source is this somewhat related answer

Joining aluminum to copper is non-trivial and must be done with care and the proper parts. Since a 240V 20A outlet has no place for the neutral wire, there's no way to do this correctly using a Cu/ALR 20A receptacle for the thing that connects to both, and that raises my suspicion that you are misconstruing a Neutral wire as a Ground wire. Mac-Blocks (which may top out at 10AWG) and Polaris connectors are both examples of connectors that can do the job (copper wire in one port at one torque value, aluminum wire in a different port at a different torque value.)

Since NEC2014 you can run a ground wire to any suitable ground without having to follow the path of the existing cable, if you don't actually have one here.

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  • Thank you for the replies, I did this 10+ years ago and wanted to get a faceplate before selling it, and then thought I need a smaller breaker, and was unsure about separate voltages. Commented Feb 29 at 18:35
  • Definitely easier to correct it before some buyer's inspector finds your past improprieties...just be sure to take care of it correctly this time.
    – Ecnerwal
    Commented Feb 29 at 18:43
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First, splicing CU to AL is no joke. I'm happy for you that you got lucky so far, but for your liability protection, it must be done correctly. I personally observe the "purple wire nuts" are not reliable, and wouldn't use them, but they are UL listed, so you can point to the UL Listing as your "get out of court free" card. Please tighten them to spec, i.e. Very Hard. When I want it to actually not melt, I recommend the Alumiconns, which are aluminum-bodied insulated connectors. Note the ground does not need an insulated connector. It might save you an Alumiconn to use a CO-ALR rated receptacle, which takes #10AL just fine. Sadly they don't make them for 240V AFAIK. If you need more space in the box, try a 2-gang Legrand Wiremold surface conduit starter box, will give you a 1" or 2" lift depending on model.

The 120V and 240V outlets sharing a circuit is called a MWBC and is fine. However, if you are trying to serve 120V and 240V sockets, you must have a 4-wire feed with separate neutral and ground. This is not optional. Honestly given the "caliber" of DIY work I see here, I would be extremely reluctant to sell without a licensed electrician giving it a makeover. This is a liability time bomb for you.

Now that you've posted photos, that really looks like SEU cable that is just poked through a 1/2" knockout and not using a proper cable clamp. That box should be dismounted from the wall, a cable clamp for that size SEU cable installed (breaking out the 3/4" knockout if needed) and remounted.

Now converting the 3-wire SEU into /2+ground is tricky. The bare mesh is neutral already, and it would be legal to strip insulation off a hot to make it ground. But even though that's Code, I think a better solution is go off Code a tiny bit, see if any wire has white stripes or simply mark it white with spiraled tape or shrink tube, and convert the bare to ground (legal per 338.10). That way you have a genuinely insulated neutral.

Neutral is not ground!!! Given that the installation is old enough to use aluminum, it may also be old enough to have a 3-wire supply from the panel with no ground. "I thought that was ground!" Nope, on a range circuit, the 3rd wire is neutral, for the oven light. Now if the neutral is a bare mesh, that's SEU cable and you can declare it to be ground per NEC 338.10.

On the 15A breaker, you can't put a 15A breaker on 20A sockets per NEC 210.23, and you have a NEMA 6-20 socket there. You can, however, have a 20A breaker on 15A sockets as long as there are 2 or more on the circuit, e.g. using the common duplex receptacle on the left.

On that cover plate, it's because you're doing it the hard way. It's harder to find a "duplex + simplex" cover plate than it is dual simplex or dual duplex. So either change the 120V outlet to a simplex, or change the 240V outlet to a duplex. Haha, bet you didn't realize those existed!

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  • I can’t remember why I put the 6-20 in there. I will pull it out. I swapped the 40Amp to a 15 amp breaker. I don’t think there is a ground, just hot/hot/neutral. Would it be acceptable to just mark the receptacle as ungrounded, I think the house was built before grounds were required. Or should I just pull one of the hots from the breaker and ground it since I don’t need two hots there anymore? Commented Feb 29 at 22:31
  • @OpieTaylor Can you pull the outlets out and get us a clear shot looking into the back of the box please? Commented Mar 1 at 4:48
  • Is the gas range staying with the house? All it needs is a single 120 V 15 A or 20 A circuit? Why can' t he use the uninsulated conductor for ground and one of the insulated conductors as the neural with whitle heat shrink (or tape?) on both ends? Pigtail with #12 or #14 copper (on the panel end too if necessary)? Commented Mar 1 at 17:39
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    @Opie You can't add a non-grounded receptacle. You can convert the 3-wire connection to hot-neutral-ground, so do that. Look closely at the SEU for white wire or white stripes on the black wire, and then wrap it with white electrical tape or shrink tubing (possibly not code depending on markings). Convert the bare to ground per NEC 338.10. Commented Mar 4 at 3:38
  • Thank you, that’s what I did, and found some aluminum 12/2 to pigtail to avoid the tricky switch to copper. Commented Mar 6 at 13:23

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