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1970 home in Colorado - I’m pretty good with copper but still learning the do’s and dont’s of aluminum.

I noticed the dryer was wired with 12/2 cu and a 3 prong outlet which seemed just bad so wanted to update.

Traced the 12-2 to a junction, where “8/3” aluminum was taped to the 12/2cu (incredibly charred I will add).

The 8/3 is two hots (30 amp double pole breaker) and the stranded loose ground (or is this neutral?).

That said - what’s the best solution here?

I don’t love shortcuts especially with big appliances, but it’s also a long run from box that’s going to be really hard to re run.

I’d like to switch dryer to 4 prong at dryer. Thank you!

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    That's 8/2, not 8/3 - grounds are not counted in numbering the cable.
    – Ecnerwal
    Jan 24, 2023 at 21:06

2 Answers 2

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That #8 aluminum with the spiral outer jacket is type SEU cable dating back to the 1960s-70s. There is absolutely nothing wrong with it if it's terminated at terminals or splices rated for aluminum and torqued to the proper specification.

There is no doubt it was there to support a 240V/30A Non-Grounded circuit for an electric dryer. For all appliances except ranges and dryers, this type of connection was outlawed in 1966, but dryers and ranges were allowed to continue, "grounding" the machine chassis to the neutral wire (what on earth were they thinking????) This too was banned in 1996 due to continuing fatalities due to lack of ground.

It sounds like you were indeed powering an electric dryer with this rig. This was inherently unsafe due to the ungrounded connection. But also had 4 code violations:

  • Improper splice from aluminum to copper
  • Too-small wire (#12 copper) handling 30A
  • Improper use of the 12/2 NM ground for neutral
  • Extension of a 3-wire dryer circuit after 1996.

Use of the bare wire in SEU cable as neutral is legal, since it's designed to be neutral and is insulated for that. SEU stands for Service Entrance Unarmored, and "service entrance" refers to the non-grounded wires between weatherhead and main panel.

Option 0: Rollback to 1973

You can shave yourself into bare code compliance by obtaining a 3-prong NEMA 10-30 socket which is certified for aluminum wire, and a torque setting tool, and reinstalling the NEMA 10-30 to the original aluminum wires in presumably the original location. This would be legal because it is "grandfathered". Replace the dryer cord with one long enough to reach the original receptacle, assuming the route is legal for a cord. Extending the dryer circuit is illegal due to lack of ground.

However, for your safety, I would recommend a different option.

Option 1: Entirely new home run using copper 10/3 w/gnd or aluminum SER

First, on the dryer, remove the neutral-ground bonding strap according to instructions. Second, fit a 4-prong cord on the dryer.

Third, run the 10/3 w/gnd to an appropriate location for a NEMA 14-30 dryer socket. Torque all screws to spec per NEC 110.14. (they figured out the torque issue on copper wires, actually.)

If you want to use aluminum wire, 4-wire SER is legal, but insurers don't like aluminum smaller than #6, and #6 is not cost competitive with copper right now. A few municipalities don't like it either.

While you're wiring a brand new 30A circuit, FYI, there is no limit to the number of receptacles on a general-purpose 30A circuit. So if you have anywhere else that a 30A circuit might be useful, like I don't know, the garage for welder, compressor or EV charging, by all means install it at this time.

By the way, home sellers report getting higher offers on houses pre-wired for EV charging. And 30A provides absolutely ample EV charging, replacing 200 miles in 13 hours on most cars. Hardly anyone needs more.

Option 2: Use the original location and retrofit a #10 ground wire.

Continue the aluminum wire in service, this time on a 4-prong NEMA 14-30 socket certified for aluminum wire.

And then, retrofit a #10 ground wire. This does not need to follow the route of the original cable, and only needs to reach any junction box with a #10 wire back to the panel, or non-flexible metal conduit back to the panel, or the Grounding Electrode System wires (which you clamp using a split bolt; never cut it).

Once this is done, the circuit could be extended by installing a junction box here and continuing; however unless you can find ILSCO Mac Block Connectors, you'll need three Polaris splice blocks at $20 a pop. Probably not worth it.

Option 3: Don't retrofit ground. Use GFCI instead.

Same as option 2, except you do not retrofit the ground wire. Instead, you install a GFCI circuit breaker. You cannot extend the circuit.

With this option it is absolutely vital that you use a 4-prong receptacle, remove the neutral-ground bonding strap on the dryer, and convert the dryer to a 4-prong cord according to instructions.

Option 4: Install a dryer that doesn't need neutral

Some of the newest e.g. heat pump dryers don't actually need the neutral wire. In that case, you can make the SEU bare wire a ground, and wire it to a 3-wire NEMA 6-30 type receptacle. At the panel move it to the ground bar (if there are separate neutral and ground bars in that panel).

This option would also work with a 3-wire 120V hot-neutral-ground connection.

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  • Thanks so much. Reevaluating options - might be worth the sanity/risk to figure out update!
    – Jimbo
    Jan 24, 2023 at 5:34
  • I'd be careful with a non-neutral dryer. Finding one that is a true 240v is surprisingly hard (because they're all listed as 240v, neutral or not)
    – Machavity
    Jan 24, 2023 at 17:32
  • @Machavity it would have to be a non-standard technology like heat pump. Ordinary heating-element dryers would all need neutral because of this. Jan 24, 2023 at 20:22
  • @Harper-ReinstateMonica, could you summarize for those of us who don't want to sit through a 25-minute video?
    – Mark
    Jan 25, 2023 at 3:19
  • @Mark what happened when you clicked the video? It is cued up to 12:36. Jan 25, 2023 at 8:07
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There is no great/easy solution here.

The old aluminum is hot/hot/neutral, which was correct at the time. Neutral is not usually bare except in service feed, but some older pre-ground cables had it that way.

4-wire is much safer than 3-wire, but only if wired correctly - i.e., separate neutral and ground.

Wire size must be 10 AWG for copper, 8 AWG for aluminum. So at a minimum the 12/2 has to be replaced with either 8/3 aluminum or 10/3 copper. If you do that, probably best would be 8 AWG aluminum so that you don't have a copper/aluminum splice, but only if you can find a matching (3-wire, ugh) aluminum compatible receptacle. Many larger receptacles are aluminum compatible but it may be more of a problem with a 30A 3-wire receptacle.

The three best solutions are:

  • Replace everything with 10/3 copper and a 4-wire receptacle. That brings it up to current code 100%. Of course, that's easy for me to say because my 4-wire receptacle is on a nipple connected directly to the panel. You don't have it quite so easy.

  • Route a ground wire by itself. I believe it has to be 10 AWG for a 30A circuit. With larger circuits you get to have a ground wire that is smaller than the hots & neutral. The ground wire does not have to follow the same path as the cable, plus it is a lot smaller than the cable, so maybe that is a workable option. Extend the 8/3 aluminum to a 4-wire 14-30 CU/AL receptacle and attach the ground wire there as well. This brings you up to current code, though it relies on that separate ground wire - which is legitimate but will look strange to those unfamiliar with it.

  • GFCI. Install a double-pole 30A GFCI breaker to replace the regular 30A breaker. Install the 4-wire receptacle but don't attach anything to the ground pin. Extend the 8/3 aluminum to the receptacle but only for hot/hot/neutral. This does not provide a true ground path for regular circuit trip, but provides the effective alternative of the GFCI for life safety. Put a label on the receptacle to indicate that it is GFCI protected but does not have a ground wire.

With any fix that includes a 4-wire receptacle, you must remove the dryer neutral/ground bond. If you don't do that then the safety features (except for increasing wire size to avoid overloads) will have no effect and in fact provide a false sense of security.

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  • Oof thanks so much. At this point I’ll evaluate running an exterior line to basement and then in with new copper. Might be cheaper / easier / safer at this point.
    – Jimbo
    Jan 24, 2023 at 5:33
  • 2
    Somewhat conveniently, at least the commonly available Leviton 10-30R is aluminum and copper compatible.
    – KMJ
    Jan 24, 2023 at 6:35

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