Help with wiring - I'm stumped for the first time

I'm hoping the gurus can help me out. A little background:

- My house was built in the 50's and had non-grounded wiring. As I remodel rooms I upgrade to wire with a ground and new circuits.

- The previous home owner (or rouge electrician) made some upgrades but I replace them where I find them as they are not to code or just sloppy or dangerous.

I am currently working on my basement and ran across a strange issue. I had a junction box that was above a light. I flipped the breaker and all the lights on the circuit went off. When I went to disconnect the wires I got a zap.

Doing some trouble shooting I found that another circuit was giving wires in the box power so I shut that off.

I traced the wires back to the original circuit and disconnected everything up stream of the box.

I got as far as I could to another junction box but now the other circuit is not working.

Here's the strange part. When I test the hot and neutral I get no current. However, if I use a ground from a known grounded source (extension wire plugged into a grounded outlet) I get current on BOTH the hot and neutral.

Hot and neutral with the circuit on - no current (ground it not touching - just looks like that in the pic)


Hot wire showing current when I connect the ground to the ground on the extension cord from a grounded outlet.


Neutral wire showing current when I connect the ground to the ground on the extension cord from a grounded outlet.


When I flip the breaker off for the second circuit I get no current - it is only when the second circuit is on.

Did someone cross a hot and neutral in the circuit? Could it be caused by my Insteon light switches on that circuit? It appears from my testing that the ground on that wire is not working as it will not show current when I connect the hot and the ground to the tester.

Any help would be appreciated!

 

BTW - You are reading voltage, not current.

Do you get any voltage between the hot or neutral and ground in the box? What about from hot/neutral to the red wire?

 

Yes, voltage - sorry.

The red wire (the entire 3wire bundle) is now out of the picture - I disconnected it from everything. That red wire controlled a light from the switch.

I just tested with my multimeter and got about 6 volts each on the wire testing the hot and neutral to the ground in the box.

 

It seems these circuits are somehow connected. I gave power to the wires in question and both circuits lit up.

However, there was only one circuit that would respond to flipping the breaker (the second circuit). The first circuit did not turn off as it used to with the other breaker.

I'm throughly confused.

 

I have run in to cases where there were two circuits in one box where power was apparently bleeding through the insulation of a wire from one circuit to the other. Separating the insulated wires solved the problem. That was in a multi-gang switch box with lights on two different circuits. Also once found a box with two different circuits where all the neutrals had been connected together. I can't say if one of those is your problem, just offering possibilities.

 

Thanks for the ideas. To confirm, the neutrals of a different circuit should not be tired together? Makes sense just want to confirm.

I did more testing and was able to get it working again. What I did is hooked everything up the way it was except I replaced the groundless wire with one that had a ground. Eveything worked as it should with the old setup and now the circuit was grounded and I was able to get a voltage reading from the hot only with the ground on that wire.

Both circuits shut off what they were supposed to but I'm not convinced this is correct. When I rewire I like to take the long route and don't reassign neutrals to ground and run sets of wire back and forth to fixtures so it is easy to see what is controlling what.

This could be perfectly valid the way it is wired, but I want to make sure before I close anything up.

 

Was that a mistype? Grounds are never used as neutrals.

 

Two other things to watch for...

In a previous house, some dope used the hot from circuit 1 and the neutral from circuit 2 when adding a new outlet for something. I was working on circuit two and had the breaker off. Imagine my surprise when I disconnected the neutral and found it was hot because it was being backfed from the other circuit.

Another situation where odd things can happen is with shared neutral circuits, where two circuits share a neutral. The two circuits have to be from opposite legs of the feed so the neutral current cancels out and never exceeds ratings, and both circuits are supposed to be on a two pole breaker or two breakers with the handles tied. But a house I worked on had several of these circuits where the breaker handles weren't tied or the ties were removed. This can lead to situations similar to those OP describes.

 

Yes - not ground. Long day

 

Thanks carbide. I'll look out for those.

 

Carbide - that was the exactly the problem. I had an electrician come out to take a look and he figured out that the neutrals from two different circuits were tied together. This makes perfect sense as I got the same shock you did closer to the panel.

What annoys me is I paid the last (licensed) electrician a lot of money to put in these lights and he screwed it up.

All is working now - thanks again for your help!