Old house, what is going on in this junction box?

[WallyWest]

I've done basic wiring, not a pro by any means. But I know enough to not electrocute myself, which is why I'm not touching this until I understand it. Pic below.

I want to replace that old black cable going from this box to an outlet over my workbench. It's the two wire, no ground type cable and everything else is modern. So just swap cables, replace the outlet with a grounded one, and we're good. Or so I thought. Then I saw that mess.

Here's where all those cables are going.

The black one, as I said is heading over to an outlet. That's it, end of the line.

The two cables coming in from the top of the box both go to the breaker box. One goes straight there, nothing else in between. This, I believe, is the line I'm actually working on. If I turn off the breaker my outlet goes dead. As expected.

But then it gets weird. The other cable also goes to the breaker box, but helpfully has a light outlet in the path. That cable, in the junction box pictured, I don't understand. The neutral wire is hanging, not connected to anything. The hot wire is spliced into the red wire heading out the left of the box. Ground is twisted together with all the other grounds.

The hot wire for the circuit I'm working on is twisted together with the hot from both the black cable and the cable going out the left of the box. Same for the neutral.

The cable going out the left of the box goes to another light socket, and then onto the other side of the basement, and ultimately up to my third floor for some reason. I know that because I have mapped out all the breakers and what they power.

If I turn the breaker that feeds the outlet I want to work on, at the other end of that black cable, it goes dead. The lights however, on both sides of the junction box stay on. I have to flip a different breaker to kill those lights. I took the twist caps off the main connections there, the two sticking down. If I kill the outlet and not the lights I get nothing on a multimeter when I check those wires. But the hot and neutral wire from the left cable, going to a light that is very much on, is twisted into those wires.

Anyone have the slightest idea what's going on here? The obvious answer is to kill both breakers, do what I need to do, and call it a day. But I'd also like to know if this is seriously messed up and I should be looking into it further. I don't understand the left cable. It's got four wires. The normal white, black, and green, and also a red that is spliced into the hot wire from the top that has a dangling neutral wire.

 

[Megawatt]

@Lucien I think that would be bad practice and help me understand that what you are saying the cable on the left is being used for one 120vac circuit and the red is carrying the other live on the top right cable which just has the neutral just floating and not hooked up

@Lucien I cannot go back to post # 7 it stops at #13

 

[Mike Johnson]

Page 1 should be available at the top or bottom of the thread.

 

[Megawatt]

Page 1 should be available at the top or bottom of the thread.

Thanks my friend for the info ?

 

[Megawatt]

The hot and neutral of your outlet circuit are both present in the cable to the left (black and white) along with the red switched hot returning to the light nearer the panel via the 3rd wirenut. But the switch is not taking its power from that black hot, because when you kill that breaker, the lights stay on. Another hot from the second breaker must arrive at the switch via a different route to power the lights.

If you ignore the red switched hot passing through the J-box to the light, everything seems normal, it's just power arriving straight from the panel and splitting to your outlet and the cable to the left. The light has its own neutral back to the panel, it's not sharing the neutral in this box as you point out the white wire is not connected. So far, there is no evidence that the two circuits are cross-connected in a way that would violate code. The pecularity is that the 4-wire cable contains hot and neutral of the outlet circuit heading away from the box, and a switched hot for the light circuit heading towards it. I am not sure if that is code-compliant if they are not part of one multi-wire branch circuit.

What would be interesting though, would be to look in the light between this box and the switch, and find out where it gets its neutral from. If it uses the neutral in this cable (which belongs to the outlet circuit) it's a cross-connection (aka borrowed neutral) and probably a violation. If a neutral belonging to the light circuit arrives from the direction of the switch or panel, again it could be OK.

Some pics of the light and switch would be revealing.

I have to agree with your post #7 and yes it is a violation of the NEC. The person that wired this was smoking some good stuff LOL. I’m like you I would like to see pictures of the OP’s light and or outlet

 

[WallyWest]

I think you guys are on the right track.

My confusion now is this. If we assume the light circuit is wired at least sort of ok, and the red wire is a switch leg for said lights, then what is the black/white pair going out the left of the box for? As far as I can tell it doesn't power anything. It certainly doesn't power the lights, because I can shut power to those wires off and the lights stay on.

I'm going to pull the light socket on the other end of that left cable and see what is going on there.

 

[WallyWest]

Ok, so this is what I have found so far. Hopefully you can read my poor attempt at a diagram.

Very top is the breaker box. The box directly below is the one from the pics I posted. So yes, I have a borrowed neutral for the light connected to that box. It gets power from 1, and neutral from 2.

Then there is 3. So when I cut the breaker to 3 ALL the lights go out, including the one up top coming out of the breaker box on 1. I suspect if I took the cover off the breaker box I would find that 1 and 3 are connected to the same breaker.

3 by the way goes on to power like half the house. This diagram is just the basement.

 

[Megawatt]

Ok, so this is what I have found so far. Hopefully you can read my poor attempt at a diagram.

Very top is the breaker box. The box directly below is the one from the pics I posted. So yes, I have a borrowed neutral for the light connected to that box. It gets power from 1, and neutral from 2.

Then there is 3. So when I cut the breaker to 3 ALL the lights go out, including the one up top coming out of the breaker box on 1. I suspect if I took the cover off the breaker box I would find that 1 and 3 are connected to the same breaker.

3 by the way goes on to power like half the house. This diagram is just the basement.

I bet you are right, I’ve opened many panels and seen many breakers double tapped which is a violation also

 

[Megawatt]

I think you guys are on the right track.

My confusion now is this. If we assume the light circuit is wired at least sort of ok, and the red wire is a switch leg for said lights, then what is the black/white pair going out the left of the box for? As far as I can tell it doesn't power anything. It certainly doesn't power the lights, because I can shut power to those wires off and the lights stay on.

I'm going to pull the light socket on the other end of that left cable and see what is going on there.

Keep in touch and let us know what’s going on. Good luck with your project

 

[Lucien Nunes]

OK, agreed, the light between the switch and the original box uses circuit 3's hot but borrows circuit 2's neutral. I was more or less expecting that.

Seems you have three choices: Pull some more cable in; make the whole shebang into one circuit (sounds like a bad idea if circuit 3 is heavily used); or change out that old cable, put the cover back on and walk away.

 

[WallyWest]

I'm going to finish what I started, and then continue mapping out how this whole mess is wired. I don't understand why they half assed it in the basement of all places. It's unfinished, exposed beams, so running a few extra cables to do it right is easy.

Considering rewiring the basement lights entirely. The circuit they're on is pretty big, quite a few upstairs rooms on it. The other basement circuit that I started working on in the first place has hardly anything on it, seems the solution is to put the basement lights on that.