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[John Roberts {JR}]

However, you have to look at the whole circuit-all the way back to the existing transformer that supplies the GFCI.  Properly installed, it has a neutral/grounded conductor (as opposed to grounding conductor) so if you touch the "hot" conductor electricity flows through you to ground-ultimately getting back to the transformer albeit through an alternate path.

If you install a true isolation transformer, there is no neutral/grounded conductor, so if you touch a hot there is no alternate path back to the transformer.  On the surface this is "safer" and some have argued that, but there are several disadvantages to this scheme.  One of the main ones being what happens if there is a short creating an unintentional ground connection.  With an intentional connection, safeguards (gfcis, breakrs, fuses) can work reliably.

I do not advise ever touching an energized conductor (transformer isolated or not). I doubt UL would either.

Inside commercial products line and neutral are both insulated, so humans cannot touch them.

JR

PS: I have killed a lot of brain cells debating with myself about the pros and cons of opening a ground path (not exactly the same thing but similar).  I had a relay inside my super-duper artist saver power drop that lifted safety ground if it detected too much ground current flowing from elsewhere (the ground lift was coincident with the GFCI disconnecting mains power.) FWIW I wouldn't even try to persuade UL to bless this while I believe it could be useful in the context of talent exposed to multiple power drops in a single performance space. UL loves their safety ground.

[Lyle Williams]

Defeating a safety mechanism is generally not a good idea.  Upstream GFCI/RCD defeat is required for testing portable GFCI/RCD.

A GFCI/RCD protected arc welder is an interesting example to think about.

[David Buckley]

A simple 1:1 transformer should just extend the GFCI current loop....

If leakage current returns to the transformer isolated neutral, that is the same as using no transformer with current leakage to the real neutral.

The difference is that the leaking neutral current back to the transformer secondary does not cause an imbalance in the primary winding oir the wire back to the source and its GFCI.

[John Roberts {JR}]

The difference is that the leaking neutral current back to the transformer secondary does not cause an imbalance in the primary winding oir the wire back to the source and its GFCI.

For that to happen chassis ground (leakage return path) is connected to the transformer isolated version of neutral.

That isn't allowed for non iso versions for obvious reasons (defeats the GFCI), same thing with transformer iso.... Connect chassis back to real safety ground and the GFCI will still trip.

JR

[John Roberts {JR}]

Had a new different outlet/GFCI failure.

Last night I plugged in my vacuum cleaner downstream from the GFCI outlet and everything plugged into the outlet went dark. The fuse for that branch was good and GFCI LED did not light. Wiggling a plug in the GFCI caused some intermittent operation but it dropped out again from a decent current load, hot water kettle.

I waited until today to swap out the gfci outlet... The screws holding the hot and neutral wires did not appear loose, but i I see obvious evidence of heating at the black (hot) screw and the screw head is discolored presumably from heating.

It seems pretty apparent this is operator error on the part of the installer (me).  But I repeat the screw did not appear loose when I removed it.

Long story shorter, I replaced with a GFCI outlet I had laying around and this is very tight fit (I need to look at sourcing a few skinny GFCI outlets for my old small junction boxes.)

After removing, replacing, and getting my kitchen back online, I wired a line cord to the suspect GFCI outlet to bench test it...

The test and reset functions work fine, but the trip LED does not light up when tripped by test button...

====
as long as I have the attention of this community, any thoughts on poking wires into the outlet clamps, or wrapping around screws. I am old (school) so wrap wires, but any thoughts on relative robustness?

I made sure the screws were tight, but like i said I thought I did that last time, and they didn't feel loose.

JR

[Stephen Swaffer]

Leviton makes some of the more compact GFCI's-cost a little more but worth it IMO.

Most GFCIs have clamps designed to have wire inserted and clamped-if that is their design, you really shouldn't wrap around the screws.  Wrapping rounf the screws with those is technically a listing violation-practically it makes them more likely to short out in metal boxes.

The trickiest part of these clamps is that the wire that is inserted needs to be straight.  It is easy to twist the wire and work it loose while installing-especially if the wire is not straight.

Also, make sure the wire is actually under the clamps.  I have a pic somewhere of a breaker where the wire was not under the clamp-never figured out how it ran as long as it did!

[John Roberts {JR}]

Leviton makes some of the more compact GFCI's-cost a little more but worth it IMO.

I just ordered a couple skinny Levitons, notably thinner and shallower than cheap GFCIs. My old house has small junction boxes and when I put a fat GFCI in my bathroom the narrow box became energized, and energized the safety ground.    (My outlet tester that I stopped pursuing detected the hot safety ground.)

Most GFCIs have clamps designed to have wire inserted and clamped-if that is their design, you really shouldn't wrap around the screws.  Wrapping rounf the screws with those is technically a listing violation-practically it makes them more likely to short out in metal boxes.

These appear designed to be used both ways... I did retighten the screws twice, but i thought they were tight the last time. 

The trickiest part of these clamps is that the wire that is inserted needs to be straight.  It is easy to twist the wire and work it loose while installing-especially if the wire is not straight.

These several decades old wires will never be perfectly straight, and aren't long enough to comfortably re-strip. 

Also, make sure the wire is actually under the clamps.  I have a pic somewhere of a breaker where the wire was not under the clamp-never figured out how it ran as long as it did!

Any thoughts about the red status LED not working? The clearly overheated GFCI outlet is in the trash already, but curious. Perhaps an internal solder connection opened up from the heating. Not sure I am curious enough to take it apart.

JR 

[Stephen Swaffer]

Any thoughts about the red status LED not working? The clearly overheated GFCI outlet is in the trash already, but curious. Perhaps an internal solder connection opened up from the heating. Not sure I am curious enough to take it apart.

Any number things perhaps-but one things is clear:  a safety device has an obvious malfunction, it needs to be replaced.  Just passing electricity doesn't make it usable!

[John Roberts {JR}]

Any number things perhaps-but one things is clear:  a safety device has an obvious malfunction, it needs to be replaced.  Just passing electricity doesn't make it usable!

Just to be crystal clear I already replaced it.... and will have better (Leviton) replacements waiting on hand JIC.

I only have 3 GFCI outfitted outlets in my entire house (kitchen, bathroom, laundry room). That is three more than many of my neighbors.

JR

[Stephen Swaffer]

I assumed you had-just a blanket principle (carry over fromo my day job in industrial maintenance).  I'd rather have a plain receptacle than a non functioning GFCI giving a false sesne of protection.

[ProSoundWeb Community]