Bootleg ground means a scenario equivalent to (deliberately) bridging the ground wire and the neutral wire.
How it was physically done (e.g. bridged screws on a receptacle, deliberately bridged wires in the wall without a junction box, or otherwise) is hard to find in a home one moves into. This DIY.SE post shows the dangers of bootleg ground: one fault can energize everything, including metal chassis. Does replacing the example’s regular receptacle with a GFCI receptacle alleviate the problem at all? This 05/30/2017, 09:39 Wikipedia entry implies it won’t, but doesn’t cite a source, so I’m not sure about its correctness.
This other DIY.SE post implies any GFCI with bootleg ground can’t be tripped by external testers but can be tripped by its own test button, but given that Wikipedia entry, I’m not sure which one is correct. If Wikipedia is correct, does that mean such GFCI can’t be tripped with either method?
I tested 2 GFCI receptacles and they’re on different circuits. I used the Amprobe INSP-3 wiring inspector circuit tester. One GFCI can be tripped by both its own test button and my circuit tester. The other can’t be tripped by either way. I measured .45 ohm ground impedance on the latter. Does that mean bootleg ground? This video says properly wired receptacles should have 1 ohm impedance. The video’s bootleg ground receptacle tested with .03 ohms impedance using the same tester. Amprobe throws a warning if it’s ≤.04 ohms.
How can I make such GFCI receptacle extend protection downstream and function properly without adversely affecting any other receptacles (on the same or different circuits), breakers, or main panel?
Is it as simple as disconnecting the GFCI's ground wire on the line side? Must I also disconnect the ground wire on the load side? Could this adversely affect bootleg-ground upstream receptacles?
Must I also disconnect all ground wires on the line and load sides of all downstream receptacles, too? Is it safe to leave said disconnected wires in the box or wall? Or, is the only solution to tear the walls apart?
Which does any GFCI disconnect upon tripping: ground, line hot, line neutral, load hot, load neutral? If tripping doesn’t disconnect ground, then wouldn’t a disconnected upstream neutral be dangerous if there's a load elsewhere on the circuit?
I’m in a guest house that has a (sub?)panel that likely sources from the old main house. The main house likely has bootleg ground receptacles and I don’t know what’s inside its panel other than it doesn’t have GFCI breakers.
The .45 ohms ground impedance was measured in the main house’s GFCI receptacle. The guest house has all non-GFCI breakers & non-GFCI receptacles, the latter of which measures .04-.07 ohms ground impedance. Are these bootleg ground? I see 3-conductor Romex when opening some of guest house's outlet covers but can’t search everything. I don’t know if guest house’s Romex is correctly wired or if it matters given main house’s condition.
Would installing GFCI breakers in the guest panel be safe or can the main house’s condition energize the guest panel?
If it’s safe, would these breakers protect everything downstream if some or all downstream receptacles or unmarked junctions have bootleg ground? Must I disconnect all downstream ground?
For the guest house, I have the same question if opting for a GFCI receptacle instead. What are the dangers of replacing a regular receptacle (that has 3-conductor Romex which might be compromised upstream with bootleg ground) with a GFCI receptacle in the middle of a circuit and connecting the GFCI receptacle’s ground?