Two wire circuit

If a GFCI is added to a two wire circuit, will the GFCI trip if there is a fault on another receptacle on that circuit?

If it’s wired properly and the fault is downsteam of the GFCI it will.

Absolutely. The ground is irrelevant for GFCI operation.

But your 3 lite tester won’t work in any downstream outlets that are 3 wire becaue the tester requires a ground to function.


and as stated above it must be wired for downstream protection…not all are

Not sure what you mean James but as long as the downstream outlets are wired to the load side of the GFCI all should be fine.

thanks exactly what I meant …I’ve seen them all wired to the line side for single outlet protection…the downstream outlets must be wired to the load side for protection…

That is was I meant, a electrician was telling one of my customers who has a two wire system she needed GFCI’s installed at all the receptacles to protect them all at a cost of $89.00 per receptacle. She probably could have gotten the entire house rewired at that cost per receptacle to just install GFCI’s.

I told her yesterday the guy was trying to rip her off, but I wanted to make sure I wasn’t loosing my mind.


I think You did your customer a good service Dale …as far as your mind goes well…that could be another thread altogether…


Tread very carefully, Dale.

There have been many instances were in order to GFCI protect an existing 2-wire circuit with a GFCI receptacle, I had to put a GFCI at each and every receptacle location. With K&T, in particular, each receptacle is tapped off the main run of K&T. No conductors exist at any receptacle location that “feed through” to the next one in the chain. Indeed, there were installers back in the day that favored this wiring methodology for 2-wire romex also. They’d run the wire into the lighting box, and drop a single romex down to each receptacle. There’s no single place to put a GFCI in such an installation to protect everything downstream. Nothing’s downstream in certain wiring arrangements; all the receptacles are essentially dead end spurs.

When you have an original two-wire system that needs this type of upgrade, it’s usually easier, and less expensive to install GFCI breakers for the branch circuit(s) at the panel.

Yah, but in the land of basements resetting them is a pain.:wink:

This is true, but if the main goal is enhanced ground fault safety, and a fusepanel exists, the requisite service upgrade/panel change required might often exceed the cost of GFCI receptacles in the right places.


I told the lady to get a couple more electricians to give her quotes, she wants to add three prong receptacles, but wanted them protected by means of a GFCI at one of the receptacles, not all of them if it was possible so the circuit is essentially protected if a fault occurred. There was no K&T in the house, just old cloth covered two wire conductors.

Right, and quite possibly all the receptacles were dead ends. It was quite popular to feed each receptacle with a drop from the light box in the room, or up from the basement lighting boxes. All I’m trying to say is that it is quite possible the sparky was not trying to rip her off.

There are no basements in Arizona----:lol:

And this house did not have any ceiling lighting except one in the living room and kitchen, the bedrooms didn’t even have ceiling lights, built in the 50’s I think.

I have to admit I never thought of that possibility…

There are multitudes of ways to wire a home no 2 electricians wire the same, some times close if they are doing track haomes or condos/apartments, you did the right thing in advising to get 2nd opinons but not to say the electrician was ripping her off.

With fuse panels up here, GFCI breakers are installed in 1104 device boxes beside the panel. Each two wire circuit feed from the panel is run through the external GFCI and protected that way without having to change out the panel.

That’s one method, but if the panel is flush in the wall in a finished area, for instance, that can get a little pricey too. There’s a way to make anything happen you want or need to happen. Some options are more costly than others.

I had been just been reading this discussion, then just Friday I inspected a house where apparently some homeowner ‘upgrading’ had been done. All of the receptacle were nice new 3 prong. A few of the newer circuits were ok but many had the 3 prong receptacles connected to the old (1970) two wire romex - even one in the garage directly below the main distribution panel! I caught it when I plugged my tester into the first front porch receptacle and took that one apart to make certain the situation was as I thought. Worse yet, a receptacle on the back outside wall was loose and had its ground terminal connected to a nearby hose bib (photo). Of course I wrote it all up recommending evaluation, etc. My question - (if I am asked) are there any locations in the home where installing a GFCI receptacle or breaker would not be ok as a solution?