It was recommended by the inspector to replace the current 2-prong outlets with GFCI outlets (grounded 3 prong was the top recommendation, but that is a bit out of budget for renovations at the moment). During the installation today, I ran into the wiring below and had a rough time getting it into the outlet (ended up doing a back wire install as outlined in the guide[0]). All seemed to be working fine and tested with the multimeter, but have been a bit paranoid about the age of the wiring...


  • What kind of sheath is around this wire? They are both black from dirt now, the wiring inside was fragile (the gentlest touch with the pliers broke off wiring tips)--is this old enough that a professional should be called to work with it?
  • Is a really tight fit generally safe? I ended up pushing the receptacle back into the box pretty forcefully to have it stay in place.


  • Leviton Smartlock Pro GFCI (20amp/125v)


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[0] https://www.leviton.com/en/docs/guidelight.pdf

2 Answers 2


All GFCI devices are able to protect portions of a circuit downline. GFCIs simply look for differences in hot and neutral current; they don't even need ground for that. Because of this, putting two GFCIs on a circuit is usually wasteful. *Connecting them nose-to-tail, elephant style, is playing a "Yo Dawg" trick on yourself! It will drive you crazy if you ever trip one of them, because they'll all trip, and they won't reset except in a particular sequence.

Install it elsewhere

Because of the above, if a GFCI will not physically fit, then you have the option of installing the GFCI protection somewhere else. You can use a GFCI breaker if they're made for your panel. If it's it's not a kitchen or bathroom outlet, you can install a GFCI receptacle somewhere, and route the circuit via that point. If it is a kitchen or bathroom outlet, you can use a GFCI deadfront near the panel.

A bigger box

Don't downgrade from a metal box to a plastic one. While the old "handy-boxes" were small and sized for their time, modern joists-and-drywall metal boxes are perfectly large. Stay with metal, not least for fire resistance (better heat dissipation) but also because some older grounding schemes depend on them. Also, plastic boxes are incapable of providing standard knockouts, and many older wiring schemes depend on them. It's not Code legal to try to cram an AC cable into a plastic box intended for NM, and that won't ground anyway! Metal boxes can be had with either knockouts or internal cable clamps, or both.

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Note that if you're changing the box, you should consider moving the box too. The wires in that box are entirely too short - they must stick out at least 3" beyond the wall surface and 6" of length past the clamp. If both cables come from the same direction, you can move the box that direction and regain some critical length.

Use a box extension

You can buy yourself some additional space in a too-small box with a surface conduit starter box, which sits about 1" proud of the wall surface. If you don't actually connect any surface conduit to it, I won't tell :)

Retrofit ground, instead

(This harmonizes well with metal boxes.)

As of NEC 2014, which California adopted, you are allowed to retrofit just a ground wire. (You are not allowed to do that for any other kind of wire, for very good reasons; but grounds only carry current during fault conditions). There are some rules.

  • The ground wire must be #14 for a 15A circuit, #12 for 20A, and #10 for 30-60A.
  • The ground wire can be bare, and routed independently from the other wires.
  • It needs to reach any of these points:
    • the panel itself, obviously
    • any other point with a large enough ground going back to the same panel
    • Any non-flexible metal conduit that goes back to the same panel (at a junction box)
    • a Grounding Electrode: bared copper wires that tie to water pipes or ground rods

Retrofitting grounds like this is often much simpler than pulling whole new cables, especially when you strategize. Start by laying a backbone of #8 or #10 ground wire to service large 30A+ appliances. Then connect up the 20A circuits with #12, etc.

Be careful not to "island" grounds, i.e. Don't hook several devices' grounds to each other but not back to the main panel. This will not ground any of them, but will simply cause them to share ground faults, so the light switch would shock you if the lamp had a ground fault. If it doesn't go back to the main panel, it's not grounded.


This is cable has a cloth sheath. These old metal boxes weren't designed for today's devices. One option is to change the breaker feeding this circuit to a GFCI breaker although these can be costly. I don't know where you live, but in our jurisdiction here in Michigan, you aren't required to replace every outlet with a GFCI, only the first one on the circuit. If you have an old fuse box, not a panel with breakers you can also replace that metal outlet box with a deep plastic rework box. This box will give you more room for the larger device. At some point, you will want to upgrade the wiring.Part #B120R

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    "the first one on the circuit". If the wiring is accessible anywhere else, even if near the fuse/breaker panel, then you could intercept it there and install a modern box and GFCI outlet. Even if you never use the outlet itself, it will provide the GFCI protection to everything on the circuit. So your old boxes can be fitted with small outlets that will easily fit. Sep 3, 2019 at 12:46
  • The GFCI protected outlets with out a ground and are updated to 3 prong receptacles need to be labeled GFCI protected , no equipment ground. The labels come in the box with the GFCI outlet & or breaker.
    – Ed Beal
    Sep 3, 2019 at 13:39
  • Thanks -- to be clear, does this mean that I could GFCI the first outlet on the circuit and replace the other 2-prong outlets on the same circuit with standard 3-prong outlets ungrounded? (I can check code later this morning, in SF Bay Area California). Sep 3, 2019 at 15:22
  • (also, I have updated the outlet with the proper stickers as you mention "GFCI Protected, No Equipment Ground", two blue stickers were placed on the lower right hand corner on the wall plate so that future inspectors will be able to see) Sep 3, 2019 at 15:23
  • You can use grounded outlets but they must include the blue sticker as Ed suggested. If any of these outlets will be powering electronics it is strongly suggested you rewire those so they are grounded, or add grounded receptacles where you need them.
    – Ray
    Sep 3, 2019 at 15:35

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