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This is not the "normal" problem of a bootlegged ground.

We have a standard old outlet box with some cloth wires, but also some bare (I think) aluminium wire hooked up to the neutral.

See photos below of the outlet (one screw removed to get a closer look at the weird ground wire) and the box with the outlet removed. Neutral is the side closest to the camera.

Outlet, one screw removed empty box

  • Does anyone have an explanation for this?
  • The bare metal wire looks rather thin. I'm not sure if it would safely carry 15A without heating up. Is it dangerous?

This aluminium wire vanishes through the back of the (metal) outlet box so I have no idea where it goes. All the wires in this box have less than 1cm of slack; it's a very weird install.

The house is ~1930s but this outlet is close to a 1990 extension and the wall may have been opened to run wires for that extension (ie. some opportunity to kludge a ground into a pre-60's system)

I'm leaning towards replacing with a gcfi outlet and leaving that weird metal tape wire alone.

Edit: here is the requested head-on shot for @ThreePhaseEel head-on shot of junction box

PS. re: electrical codes this is NE USA.

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    That might be the bonding wire included in type AC or MC cable - it should be connected to the box (which then grounds the device) - definitely not joined to the neutral. See diy.stackexchange.com/questions/223574/… for an image.
    – nobody
    Commented Sep 6, 2023 at 1:18
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    Two wire is hot and neutral. Three wire should be hot/neutral and ground. If it is ground, it should not touch neutral. A good ground should read 120v between hot and ground and 0v between ground and neutral. It could be an added ground in a bad case of making that outlet safer.
    – crip659
    Commented Sep 6, 2023 at 1:31
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    Can you post a photo looking squarely into the back of the box please? Commented Sep 6, 2023 at 2:28
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    @kreemoweet -- when a bonding strip is present, it needs to be cut back, yes, but the bonding strip in conjunction with the cable armor forms an approved grounding means, so the outlet can be safely grounded to the box provided the armored cable is terminated to the box using a suitable fitting Commented Sep 6, 2023 at 11:37
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    @ThreePhaseEel probably wants to see how the cable is connected into the junction box and if the "bonding" strip is part of the group.
    – JACK
    Commented Sep 6, 2023 at 13:17

1 Answer 1

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You asked two questions:

  1. Explanation

Rather than aluminum, I suspect the the mystery wire may be a tinned copper conductor from the knob and tube era, when wires were often joined by soldering. If so, it would have been insulated. However, the old insulation becomes brittle with time and sometimes abrades off when the wire is manipulated, e.g., when pulling it into boxes and moving it from old to new outlets.

  1. Is it dangerous?

I would not say it is safe. What you are seeing could be the tip of the iceberg. It looks bad and what's behind the walls could be worse.

If it were my house, I would replace the wiring from the last sound point in the system (or run a new home run to the breaker box) with 2+g cable to current code. I would also replace whatever this box feeds in the same way.

(I am not an electrician, but I have studied the code and best practices in order to update and add circuits in old houses from 1890 to 1950, particularly with regard to knob and tube.)

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