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I'm replacing a few 2-prong receptacles with GFCI ones in an old house. My understanding is that ideally we should identify head of circuit and only replace the head receptacle with GFCI one, while replacing downstream 2-prong receptacles with regular GFCI ones.

However since it is an old house and I might not be able to identify all head circuit correctly. I'm wondering if is it ok to replace all 2-prong receptacles with GFCI ones, is there any downside besides higher cost on GFCI receptacles?

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  • There is no reason you should have trouble figuring out what receptacles are on what circuit or in what order, although it is a fair bit of work. That said, a common solution is to mount boxes near the panel and run a wire with ground to each box so the GFCI is grounded and put each two wire circuit on the load terminals of those to keep your reset apparatus in one place. Or just use GFCI breakers. – K H May 11 at 5:47
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You can do it either way. You can...

Install GFCI receps everywhere you want them. Never use "Load".

In this case you spend $16 per outlet. Every outlet is responsible for its own GFCI protection. Therefore you do not use the "Load" terminals at all. Don't even remove the "For Wizards Only" warning tape.

Since the outlets are not grounded, you will need to use the "No Equipment Ground" stickers on each one.

The upside of this method is you never have to go hunting for the reset button, you know exactly where it is.

Or...

Install 1 GFCI recep at head of circuit. Use "Load" as intended.

The "Load" terminals have exactly one use: to extend GFCI protection to a circuit downline. They should never be used for anything else.

So having found the correct outlet, guess which wires come from the panel, and attach them to "Line". Cap off the others temporarily. Power up for testing and if the GFCI works, you guessed right.

Now attach the remaining wires to "Load".

Affix a "No Equipment Ground" sticker here.

All other plain receps that trip with this GFCI get "GFCI Protected" stickers and "NO Equipment Ground" stickers.

The upside of this is you only need 1 GFCI per circuit, so fewer GFCIs to test every month.

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If you want, you can certainly put GFCI outlets everywhere. Just be sure to not use the LOAD terminals on any of them. Instead, use pigtails to connect both incoming wires and outgoing wires to the LINE terminals. If you have any outlets where multiple hot and/or neutral wires connected (any the tabs are not broken), do not use the LOAD terminals to reproduce that.

Having said that, it's not that hard to eliminate the need for many GFCI outlets. Start with an outlet in a room. With the power off, remove it from the wall and disconnect all of the wires (make sure you note how they were connected if the colors are not obvious) and cover them with wire nuts. Turn the power back on and see which outlets are now dead: these are all downstream and can be replaced with normal 3-prong outlets, labeled "GFCI protected/no ground". After idntifying the incoming wires (with a voltmeter or non-contact tester), turn the power back off and replace the outlet you pulled with a GFCI outlet. Make sure to connect the incoming wires to LINE and outgoing to LOAD.

Now try another outlet, if it turns out that a new GFCI outlet is downstream, either make that an isolated GFCI or go back and replace the downstream GFCI with a normal 3-prong (labeled).

Don't forget to label all GFCI outlets "no ground".

One warning: if you try to use an outlet tester with a GFCI trip button to test your wiring, such as enter image description here be aware that this will not work without a ground. You can get around this by using a long wire with one end connected to a ground (a water faucet my work) and the other end connected to the tab on a 2-3 prong outlet converter enter image description here and plug the tester into that.

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