Multi-circuit wiring mystery

Old 07-04-02, 07:57 AM
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Question Multi-circuit wiring mystery

While redoing a kitchen in a rental unit in a five floor townhouse (built 1882 - remodeled n times), I noticed the refrigerator outlet sparking when I unplugged it. When I opened it and investigated I found three different circuits in the box. Circuit 7 had a secure wire-nutted junction of a red hot and a black hot, with the neutral to the outlet. Circuit 9 was normal, hot and neutral to the outlet. Circuit 6 had the neutral to the outlet and the hot uncapped and unstripped but with the end sporadically touching the metal box. I capped off the loose hot, but when power was restored many downline outlets were without power. No wires fell out of the box, and I'm pretty sure the loose hot was loose before I opened the box up, and I found no copper ends in the box. Although I'm fairly experienced with ordinary electrical work, I don't know what to look for or how to think about solving this one. Grateful for any suggestions.
Old 07-04-02, 10:19 AM
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REmove each wire nut separately and replace with a new one to ensure a good connection. When the wire nut is taken off look for a little piece of wire that is connected to nothing. Chances are your loose wire was shorted and burnt in two causing your flash. IF you find that little piece of wire I suspect you will have found where that loose wire is supposed to have been connected to.

I would be concerned with what you are discribing that you may have a device box that is way over full with conductors. Is this the case?

Old 07-04-02, 10:40 AM
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I looked closely for traces of a broken/vaporized wire in both the wire-nut junction and the outlet but found nothing. In frustration,I tried to guess at the connection and connected the Circuit 6 hot to the Circuit 7 wire-nut, and the downstream outlets worked but with something like 190v. With power off, I tested for continuity between the hots in the troubled outlet box and the downstream outlets, and found continuity between both Circuit 6 hot and Circuit 7 hot to one side of the downstream box. The box is indeed too full - hopefully I can correct all the faults when I figure out the problem. Mike
Old 07-04-02, 12:11 PM
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Never guess. Worst case, your guess might work. But not everything that works is safe by a long stretch. You might guess at something that works correctly, but then will burn your house down six months later.

And never connect a wire from one circuit to a wire from another circuit. When you do this, you can get pseudorandom voltages anywhere between 0 and 240 volts. This means that you will either ruin appliances in your house, kill yourself, or burn your house down. None are good choices.

Continuity test are not usually very useful, unless conducted in very controlled conditions, usually by disconnecting all wires and shutting off all breakers before conducting the test. You'd be surprised how many wires in your house will show continuity with each other.

When diagnosing jumbles such as yours, it usually takes a quaified person on site to make any sense out of it. There are too many unknowns in the facts that you are presenting to us. We don't know how you are making your judgements, or the exact conditions of the tests you are performing. Tests can be quite misleading when not conducted under just the right set of circumstances. You are also likely making assumptions without even realizing that you are making them (e.g., how are you sure you know which one of those wires is really the circuit 9 neutral?).

Good luck.

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