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drzap · Joined: 11 Jul 2005 Posts: 1

i'm helping someone update the branch circuit wiring in their older house. i successfully ran new wire to most circuits, but there were two knob-and-tube cicuits that i was unable to rewire as they move to the upper stories of the house and the owner doesn't want to open any walls.

my solution to make these circuits "safe" was to install GFI receptacles in the basement to ground fault protect these circuits. i cut the wires for each circuit and ran the wires for each into a junction box. i correctly wired each GFI receptacle in its junction box

everything went fine when i powered up the first circuit. when i powered the second circuit and reset the GFI it not only tripped itself but it tripped the other GFI which is a totally separate circuit.

thinking it was a faulty GFI i removed it and hard wired the circuit back together. when I replaced the fuse it tripped the other GFI again.

what gives?

one thing i noticed that may or may not be relevant is that the two circuits come together in one double gang switch box on the second floor--one switch on the first circuit operates an overhead light while the other switch on the other circuit operates a bathroom light. i didn't see wires touching inside this switch box, though.

any thoughts/solutions to this problem would be appreciated. i could return circuits to their original condition, but there is obviously a small ground leak somewhere that needs to be fixed in order to make the house safe.

b · Posted: Wed Aug 03, 2005 1:17 pm Post subject:

Knob and Tube frequently run in and out of circuits and is very hard to decifer. It could be that somewhere the second circuit is running nuetrals with the first circuit. It would be best to run new wire. Can you get to the attic and down the wall from there so as not to open the drywall? Sorry to not have a more concrete answer for you.
B