2 interfering circuits-a mystery

[Aaron1877]

I have a lot of previous experience wiring my own houses and for friends and have always passed inspections etc. This time I roughed the wiring in a small house for a friend from the outset. On completion of the rough in I turned the breakers on to check for any shorts and obvious problems, found none, I cant remember if I turned each one on, and off one at a time or turned them all on and then turned them all off.
SO now the house has had drywall panelling installed and painted so I have filled the boxes and installed lights etc All the circuits are fine except two. There is no load yet on any of these two circuits. Circuit number two and number four which are on opposite legs will not stay on at the same time. Circuit 2 is a bedroom, plugs and lights and circuit 4 is plugs and lights for the adjoining living room. The two circuits share some holes drilled in the studs for a distance as the rooms are off in the same direction from the distribution center. If I turn on number 2 it powers all the things connected to both circuit 2 and circuit 4. If I turn circuit 2 off and then turn on the breaker for circuit 4, it also powers all the things on circuit 2 and 4. When I try to turn on the breakers for both circuits, they blow. Not sure what is happening here but I suspect a screw or nail piercing both wires or a staple.What else could it be??? I have checked every box for a mistake in connections and find no errors. the two circuits do not mistakenly join in any box or fixture. So how do I trouble shoot this and how do I locate the location of the problem??????

 

[Idmason60]

It sounds like your bucking phases, tying to connect two opposite buss from the panel and tied together in a box someplace . You would know the two circuits are tied someplace because they would trip when you turn on the both breakers.
Your going to need to test every circuit on both breaker for place where two black wires from both phases are tied together.
You need to be careful with this. Your hazard is that you will have 220 volts in that box. Be careful if dealing with
the box hot.

.

Larry
S.Florida

 

[Don Farrell]

I hope you have a meter. If not get one.

First, check the voltage for each outlet that is affected by this problem. If you find any with 240Vac then you have either lost your neutrals or cross connected them somehow (which I doubt since you say the branch circuits don't meet in any of the outlets)
If you find no voltage issues, go to the panelboard, turn it off and pull breaker 4 off the panelboard. Turn the panelboard back on and re test the circuits. If they are all still on you have two choices, use the Ohm's on the meter and see if you can find any place where the line meet up or get an electrician to do the work.