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With normal receptacle at first device in circuit all works fine--all lights and both receptacles. (I inherited the circuit--didn't do it myself.)

I thought, "Why not install a GFCI as first device?" to provide protection to the two receptacles that are the 3rd and 4th devices in the circuit.

Well, neither of two NEW GFCIS even acknowledge that there is current being supplied to them. (I assure you that there is 120v there.)

A friend wasn't sure but guessed that the GFCIs are saying "I can't help you with lights; receptacles only."

I obviously didn't know that, but it makes sense. There's no way to provide GFCI protection for lights anyway (I assume).

I've Googled a fair amount and followed many links, but have yet to find someone saying "GFCI is wired to not let this situation work." Every one either "it's okay but it's against code so don't do it" or similar hedging.

Whatever, I'm going back to the normal receptacle where I was on Monday with everything working. BTW, a GFCI tester showed no red and two yellows, which means "CORRECT" for this particular tester.

My only question is: forget code for the moment--should the two GFCIs have worked?

Lights?

A GFCI can protect lights. You just usually don't need to protect lights. Lights that are installed out-of-reach in the ceiling are normally not required to be protected by GFCI simply because GFCI would not help. GFCI protects against current leaking through a person. If you can't touch the light, no current can flow through you. There are some exceptions: lights above a tub or shower and some outdoor lights, especially if near a pool or other water.

However, there is nothing wrong with GFCI protecting lights. Just keep in mind that:

• If your lights & receptacles in a bathroom are on the same circuit and the lights are protected by the same GFCI that protects the receptacles, then if the GFCI trips, the lights will go out. You might be holding a hair dryer or other device that, while at that point no longer an electric shock hazard, might still not be a good situation in the dark.


• If your lights use a smart switch that relies on leaking a little current to ground, that could cause nuisance trips of a GFCI.

Line vs. Load

With a regular (non-GFCI) receptacle, you typically will have "incoming" hot/neutral and "outgoing" hot/neutral, and it doesn't matter which wires go to which screws, as long as you get "hot" vs. "neutral" correct.

With a GFCI, it matters. A lot.

• Figure out which set of wires is "incoming" - i.e., hot/neutral coming from the circuit breaker. There are a number of ways to do this if the wiring isn't obvious. I would turn off the breaker, disconnect all the wires from the receptacle, cap them for safety, turn on the breaker and check with a non-contact tester.


• Connect the "incoming" wires to the LINE side of a GFCI receptacle.


• Test the receptacle - it should work fine with normal loads. TEST/RESET should work for testing the GFCI functions, as well as a "GFCI tester". If you have problems at this point then your wiring is really messed up or you have a bad GFCI receptacle.
  

Now that you have the LINE side working, connect the remaining hot & neutral wires to the LOAD side of the GFCI. If it trips immediately then you have ground fault somewhere in the existing LOAD-side wiring (the lights or other receptacles). If it does not trip then use a GFCI tester to test from each of the other receptacles to make sure everything is good.

FYI, the lights on the "GFCI tester" have absolutely nothing to do with GFCI. The tester is really two functions stuck in one convenient package:

• "Magic 8-ball" (Harper's term) tester for hot vs. neutral vs. ground connections. Not 100% reliable for diagnosis of a particular problem, but very useful for basic testing.


• GFCI tester - drains a small amount of current from hot to ground to test GFCI functionality.

Your idea is fine

Using a GFCI device in the first position to protect the entire circuit is a perfectly fine idea. It will work if the device is wired correctly and the rest of the circuit is (already) wired correctly.

Lights definitely can be placed on GFCI (it just doesn't buy you much if they are also grounded).

Both sidestep accidental "Line vs Load" swap and test the downline circuit

Where this usually goes wrong is the "For Wizards Only" warning tape. It covers up the LOAD terminals (though we have seen one that covered LINE by mistake).

My trick of hooking up GFCIs is to leave the warning tape in place and connect LINE first. Cap off everything else, and power up. The GFCI socket should be able to power an appliance, test, and reset.

If more than one wire needs to go to a LINE terminal, I recommend pigtailing rather than using the GFCI as a splice. That way you can test the circuit with the GFCI omitted altogether, and test the GFCI after that all checks out. (Most GFCIs support screw-to-clamp to allow 2 wires to be back-wired under each screw; those are fine but never use backstabs as they are unreliable and not made to be used twice).

What is the point of this? Am I worried about you confusing LINE vs LOAD? No, I'm worried about the downline circuit having an issue that trips GFCI. If you hook it all up at once, you won't be able to distinguish a bad GFCI from a bad downline circuit.

Once all that checks out, everything hooked to LINE is frozen. It will not be removed from LINE. Now you tear off the tape and add any hot-neutral pairs to LOAD. Then you power up and test again. If you have any problems, you know the LINE wires were not the problem, so you focus your troubleshooting efforts on LOAD. And it can be a pre-existing defect in downline wiring, e.g. A bootlegged ground or shared/borrowed neutral.

By not hooking up all 4 wires at once, you avert the common mistake of hooking LINE wires to LOAD and vice versa. A modern GFCI will not power up in those conditions. An old one will, but TEST/RESET won't work.

You can indeed install a GFCI as a first device, but you need to know which are the incoming "Hot" (usually black) and "Neutral" ( white).
As well and hopefully, there's a associated ground ( usually bare copper wire )

Lighting can be protected, but there would have to be a reason. And that would be " Can a person come in contact with a light fixture ". I do know in a couple cases where in very big / expensive homes I have seen enormous sized bathrooms with a table / chair and a table lamp wall outlet which was switched from a wall switch... "That" would be one scenario where lighting would be protected from a GFCI.
Anyways..
Note that on the GFCI Outlet connections are labeled "Line" and "Load".

All above being said you need to establish which wires are indeed your incoming power. Home Depot / Lowe's sells proximity / non contact testers as well as the meter types.

Always turn off the source power before you attempt any work.