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I have read through a lot of discussions on GFCI protection for old 2-wire circuits that don't have a ground wire; most discuss installing a GFCI outlet when replacing an original 2-prong outlet, and labeling it "not grounded."

However, I wanted to make sure that another method is acceptable under NEC 2017/2020: Using a GFCI (or combination GFCI/AFCI) breaker on the whole circuit, and upgrading the old 2-prong outlets to modern 3-prong (tamper resistant) outlets.

  1. Is the GFCI (or GFCI/AFCI) breaker and 3-prong non-GFCI outlet combination valid?

  2. Since most of these situation will occur in homes with metal outlet boxes, should the grounding screw on the 3-prong outlet be tied to the metal box with a green grounding screw? My hunch tells me "no" as this wouldn't be the case with a GFCI outlet scenario, but please correct me if I'm mistaken.

  3. If the entire circuit is verifiably composed of AC wire that has the thin metal strip inside, and is properly pulled/connected through those same metal boxes, does it change the answer to question 2), whether the replacement outlet is GFCI or a regular non-GFCI 3-prong?

Many thanks,

sil80

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    #3 if the circuit has a confirmed ground path, then should not need the no-ground label and attaching ground to new outlets is good. Should only have one GFCI protection device(breaker or a GFCI outlet) on a circuit.
    – crip659
    Oct 13, 2022 at 12:48

2 Answers 2

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NEC 2020 section is 406.4(D)(2) and gives 3 options:

(a) replace a non-grounding receptacle with another non-grounding receptacle.

(b) "A non-grounding-type receptacle(s) shall be permitted to be replaced with a ground-fault circuit interrupter-type of receptacle(s) ... An equipment grounding conductor shall not be connected from the ground-fault circuit-interrupter-type receptacle to any outlet supplied from the ground-fault circuit-interrupter receptacle"

(c) "A non-grounding-type receptacle(s) shall be permitted to be replaced with a grounding-type receptacle(s) where supplied through a ground-fault circuit interrupter ... An equipment grounding conductor shall not be connected between the grounding-type receptacles."

So, your (1) is allowed under 406.4(D)(2)(c) since the GFCI breaker is a ground-fault circuit interrupter.

For (2), if you don't know what might be connected to the metal outlet box, well, don't risk accidentally connecting grounds between outlets which is not allowed ("shall not").

For (3), there are requirements on the size of a grounding conductor, so you would need to check the size of that "thin" conductor.

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  • Much appreciate the input!
    – sil80
    Oct 14, 2022 at 16:09
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Is the GFCI (or GFCI/AFCI) breaker and 3-prong non-GFCI outlet combination valid?

Yes, IF the receptacles are labeled "GFCI Protected" and "No Equipment Ground".

If you find the provided blue labels to be unsightly, feel free to laser etch your own receptacle covers, use Brother/P-Touch labels that match the white cover, or whatever floats your boat. It must not be hand-written.

Since most of these situation will occur in homes with metal outlet boxes, should the grounding screw on the 3-prong outlet be tied to the metal box with a green grounding screw? My hunch tells me "no" as this wouldn't be the case with a GFCI outlet scenario, but please correct me if I'm mistaken.

Forget the green ground wire. The GFCI receptacle is labeled "Self-Grounding", which means it will electrically connect its ground to the box's ground automagically via the mounting screws. There is never a need for ground wire to the receptacle, unless the box is plastic.

Metal boxes are awesome.

Let's get clear on the grounding rules with metal boxes.

  • Rule #1: Ground wires from the panel/cables must go to the metal box FIRST. This grounding must remain functional even if the device is removed.
  • Rule #2: Switches automagically pick up ground via mounting screws. Receptacles labeled "Self-Grounding" do the same. Receptacles with hard, flush bottomed-out clean metal contact between box and yoke pick up ground that way. Only cheapo receptacles suspended above the box via drywall ears need a ground wire run.

If the entire circuit is verifiably composed of AC cable that has the thin metal strip inside, and is properly pulled/connected through those same metal boxes, does it change the answer to question 2), whether the replacement outlet is GFCI or a regular non-GFCI 3-prong?

If AC cable is used which has the grounding strip, AND correct fittings/connectors are used to adapt it into the metal box, then that constitutes a valid grounding path and serves as the ground. This ground is equal to the kind with wires.

The metal strip interacts with the correct connector, causing the grounding. Don't use it like a ground wire from Romex.

Some might say superior, since it reduces clutter inside the box.

Turns out those old people did know a trick or two lol.

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  • Harper, thank you so much, as always. Just wanted to clarify, if a switch, or a GFCI (or a "Self grounding" labeled-receptacle is mounted while offset by drywall, it is NOT grounded properly, correct? One would have to use the green screw on the side of the switch/receptacle?
    – sil80
    Oct 15, 2022 at 16:01
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    @sil90 actually it is grounded correctly, since those things are allowed to pick up ground via the mounting screws which screw into the metal box. That is a feature of those better receptacles (and switches are always allowed to do it). Oct 15, 2022 at 19:58

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