The wall box is from the mid-1950's and my multimeter shows that it is grounded. There are a solid 120 volts when testing between live and ground. I noticed a bare copper wire coming from the cloth wiring in the back tied to a screw connected to the box. I looked around for usable screw holes in the box to screw a ground screw into but they were all way too large. Does this look okay? I get good continuity here between the green insulated copper ground wire I added and the rest of the box. The green wire will go to the grounding screw on the outlet. ground wires

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    Hey, making fixes and assembling new wires or other parts is strictly regulated in many countries. Inserting a new wire against the current technical rules or without having the needed license for the job (no matter how well the actual job is done) at least invalidates fire and accident insurances. If something happens or one gets caught from doing unlicensed job, the next episode can be in a court of law. This is true where I live. GET PRO HELP! Even in case the normal habit in your country is to pay the usual bribe and do the job as you like, think the safety first. – user287001 Jan 6 '20 at 8:31
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    (Continued) A wire under a screw is an unacceptable connection where I live. There should be parts which prevent the wire sliding sideways further from the screw. – user287001 Jan 6 '20 at 8:35
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    Please edit to include your country (USA, EU, etc.) because there are differences between wiring codes – MarkU Jan 6 '20 at 8:44
  • @MarkU looks pretty much like standard North American rework device box to me. There could be a green screw under that cable on the right. If not - replacing the box with new one is not that hard – Maple Jan 6 '20 at 9:44
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    OP please do not crosspost multiple copies of a question to multiple communities. They will all get migrated to the right community, where it makes a mess. – Harper - Reinstate Monica Jan 6 '20 at 16:51

Purely technically this is an unreliable connection. Think if your screw is a little conical, the wire can slide further from the screw and become loose.It can take weeks or months to be noticeable. There should be parts which prevent the the wire sliding between the surfaces. In developed countries there should be used certified connection boxes if one extends old wirings.

There should be parts which prevent the bending, rotating and pulling of the wire near the connection. Unprotected wires should be inside a closed space which is inaccessible without using tools.

Electrically acceptable grounding must be built to have low enough resistance. That can be true for the existing old grounding, but inserting wire length can be invalid due the maximum allowed resistance. A multimeter is useless for checking this.

Finally the job without license can be illegal even in case you can do it technically perfectly. Technically perfect is not purely reliable contacts, low enough resistance and good insulation & protection. There can be a regulation which states that old wirings aren't allowed to be continued, the whole branch should be rebuilt starting from the line breaker box and by using only currently valid parts.

  • You're kinda making this stuff up, aren't you? – Harper - Reinstate Monica Jan 6 '20 at 16:50
  • I do and have done electric works as a paid worker, I have no right to be a contractor , a single wire assembled by myself in any building as an independent builder or repairman will be illegal. – user287001 Jan 6 '20 at 17:46
  • That's true. However, many jurisdictions have an exception, which permits self-repair by homeowners. The general concept is the homeowner has personal stake in the quality of the repair. However, this has no effect on the requirement for permits for work of any scale. – Harper - Reinstate Monica Jan 6 '20 at 17:59

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