trouble shooting a short, i am confused.

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Old 03-29-18, 01:10 AM
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trouble shooting a short, i am confused.

the short version of the story leading up to my current problem.
a circuit in my house has old style BX ,(without the ground wire) , ungrounded outlets, at the end closest to the breaker panel and romex with grounded outlets at the end of the circuit. three rooms are on the circuit.

breaker tripped, would not reset. decided to replace the old BX with romex and grounded outlets.

first outlet i put in was a GFCI so it would protect the rest of the circuit.

i did one thing at a time, tested new work, then went on to the next one. this was in case i screwed something up,i would know it was the last thing i worked on.

i get to the existing romex, connect the new romex, and when i reset the breaker, the GFCI trips.

all of the wring in the existing room is connected together at the ceiling light fixture. i disconnect all of the wires, GFCI resets.
i reconnect each wire one at a time to the wire that feeds the power in to the junction box. two of the three , the GFCI would not reset. the third, the wire to the light switch, the GFCI reset, but tripped when i turned the light on.

before i assume a squirrel got in my attic, chewed through all three wires so they are touching and causing a short, does anyone have any idea as to what could be wrong?

what would someone, who knows what they are doing, check at this point?

is it possible to have too many light fixtures and outlets on one GFCI?
 
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Old 03-29-18, 01:46 AM
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before i assume a squirrel got in my attic, chewed through all three wires so they are touching and causing a short,

Shorts trip breakers not GFCIs. GFCOs are tripped by an imbalance of current between hot and neutral.

the wire that feeds the power in to the junction box. two of the three , the GFCI would not reset. the third, the wire to the light switch, the GFCI reset, but tripped when i turned the light on.

(Those are cables not wires.) Are all the cables at the ceiling new or is the cable to the switch original.
 
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Old 03-29-18, 02:49 AM
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all of the cables that are tripping the GFCI are about 10 years old.

I had a circuit with old style BX in one room, and 10 year old ROMEX in another room.
i removed the BX and now have new ROMEX connected to 10 year old ROMEX.
i also added a GFCI
 
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Old 03-29-18, 02:56 AM
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Originally Posted by ray2047 View Post
Shorts trip breakers not GFCIs. GFCOs are tripped by an imbalance of current between hot and neutral.




(Those are cables not wires.) Are all the cables at the ceiling new or is the cable to the switch original.
wait. imbalance of current.

i tested these cables by disconnecting all of the hots and leaving the neutrals and grounds connected. i then connected the hot, one cable at a time.
would leaving all of the neutrals and grounds connected trip the GFCI?
should i try again with only one hot, neutral and ground connected at a time?
 
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Old 03-29-18, 03:02 AM
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should i try again with only one hot, neutral and ground connected at a time?
Yes, that is the most accurate way.
 
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Old 03-29-18, 10:12 AM
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Since you aren't tripping a breaker.... your problem is most likely a white neutral wire touching ground.
 
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Old 03-29-18, 05:07 PM
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i got it.
disconnected everything in the ceiling box, connected one at a time, GFCI only tripped on one cable, so now i know where the problem is.
i didnt realize the GFCI did that good of a job.

thanks everyone.
 
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