Oops, forgot to say:
If you get the same pattern of hot wires for either breaker, then the two circuits are joined in a junction box somewhere (or worse, buried in a wall.) You’ll need to go junction box hunting. They can be in curious locations.
I assume you have an AC voltage detector. If you do any wiring at all, you need one.
Here’s how it should be wired: http://www.act-remote.com/PCC/images/fig2_07.gif
Yes, of course, but I was asking about having two circuits in a single junction box, not tied together.
ETA: Yeah, that wasn’t worded correctly at all. Sorry. The sentence in this post above is what I meant. Two separate circuits not tied together.
this involves a 3-way switch and there are at least 5 ways to wire up a light this way. I would focus on the the light and the 3-way switch wiring.
All I can think of is that somebody used a junction box for more than one line and tied 2 live leads together thinking it was part of a chain.
That’s fine and is done all the time.
What does come into consideration is # of wires and the size of the box.
If I was working on this funky fixture I would flip the master breaker to the entire house to (hopefully) ensure the fixture has no power whatsoever.
I’ve always separated them and I routinely come across boxes next to each other in other houses. It keeps thing neat and avoids problems like this. Assumptions can’t be made. One box one circuit. It may be legal and at times necessary due to space but it’s not preferred.
Thanks for that!
Some of the options I get an immediate intuitive sense for, but others not so much. I’d love to see schematics rather than drawings; they’re a lot easier to understand. I may bother to draw them myself, just to shed some light on the subject.
Regardless of how they’re wired, following my method above will show whether the problem is in the 3-way wiring or in an external junction box. If the power always appears at the same locations (based on switch settings) regardless of which circuit is on, the problem is outside the 3-way wiring. You can optimize this with more understanding of how the 3-way is wired.
For example, if only one power cable attaches to one of the switches, it’s a tail-end, and you can ignore it. Well, sorta …
It certainly avoids problems for amateurs like me!
Some things I’ve learned about the difference between people who have an electronics background and practical workers who don’t (electricians and auto mechanics)…
Most electricians and mechanics can’t read a schematic to save their lives. They like point-to-point diagrams, if not pictorial representations of circuit boxes, connectors, etc.
DIYer’s are even worse and need photographic images.
DIYer’s are afraid of wiring. Very afraid. This is not an entirely bad thing.
Most mechanics are terrified of electrical systems, which is just plain weird. I’ve seen guys who would climb under a running dragster to reach up past glowing exhaust pipes and in between running pulley sheaves to tweak something… but treat a taillight circuit like something from the Necronomicon.
Would a circuit tester catch this problem? you could remove the bulb and screw in a socket adapter.
I’ve had a tester for about 15 years to check receptacles. Open neutrals, open grounds, it checks for several problems.
Not preferred? By whom? What are you talking about?
If we had a preference we wouldn’t use junction boxes at all.
a person should check all wires in a junction box, with a noncontact voltage tester, before touching bare wire or terminals. this will alert you to multiple circuits in a box or mislabeled circuits.
