Backfeed, 2 120 volt circuits tied together

[Eddie702]

I was testing unmarked 120 volt circuits in a panel to find the circuits/loads to transfer to a generator sub panel.

I clicked each circuit off waited for a "it's off" response and getting none turned it back on and moved on to the next circuit.

Found a circuit that would not go dead..

Finally found power on the load side of a breaker that was off.

Removed the breaker and ohmed it out and it was ok so I assumed it was a backfeed 2 hots from two different circuits tied together

We found the two offending circuits and luckley they went from the basement panel up inside the kitchen outside wall to the attic (1 story house). One circuit was the red wire of a multiwire cable (3 wire romex) & the other was a black in a two wire cable.


We lost where the two wire cable went, but followed the three wire to a 4 x 4 box that was a light in a closet. Found the red wire nutted to a black from a two wire cable. Removed the wire nut and the backfeed went away, everything in the house still worked.


We were lucky we had exposed cable in the attic to follow.

Funny thing is the house was built in 1969. The wires in that ceiling box had ceiling spray still on them didn't look like anyone had ever been into that box since the house was built so I guess the "backfeed" was always there. Luck or no luck that they were on the same phase, If they were not that would have been a short they could have found

 

[480sparky]

I usually find double-fed circuits in multi-gang switch boxes. IE, the general lighting circuit for the hallway & bedrooms and the circuit for the living room and kitchen lights both are in the 2-, 3- or 4-gang box at the end of the hall that feeds the wall 3-way, the living room light & fan and the can lights over the fireplace.

 

[ptonsparky]

The guys doing houses for one of the shops I worked for back in the last century, were fast. That’s about all I can say about them. Stuff happens occasionally, fortunately.