Smoke is bad.

I have a juction box in the ceiling. There are four 2/12 wires comming in.
#1 comes from the electrical panel
#2 goes to a light switch
#3 goes to a wall outlet
#4 goes to track lighting 5 feet away.

Everything was working as expected. The switch, lights and the outlet showed proper wiring when tested.

When making the connections in the juction box, I matched up the colors of wire #1 and #3 with a jumper from each. I used a wire nut to make the connections.
When I turned the circut on at the panel everything seemed fine. Then the black wire started smoking at the connection I made in the junction box. I immediately turned the breaker off! When I looked at the wires the nut was melted. The breaker seemed OK although it did not trip.

What might have caused this?
Everything had been working for days.
Should I try it again?
What, if anything, do I need to replace?

Thanks

 

Any chance you have a Federal Pacific panel? What is the size of the breaker on this circuit? Were cables #2 and #4 still disconnected when you made this test? If not, how were those connections made? What do you mean by a jumper and what was its purpose? Was there anything plugged into the breaker? Are you 100% sure about where each cable goes, and how can you tell? What does "showed proper wiring when tested" mean exactly?

We need details.

 

>>Any chance you have a Federal Pacific panel?
Cutler-Hammer

>>What is the size of the breaker on this circuit?
20 Amp

>>Were cables #2 and #4 still disconnected when you made this test?
Yes

>>What do you mean by a jumper and what was its purpose?
The correct term is pigtail. Sorry.

>>Was there anything plugged into the breaker?
A small radio

>>Are you 100% sure about where each cable goes, and how can you tell?
Yes. 100%. I have been in the crawl space. Followed each cable to it's destination.

>>What does "showed proper wiring when tested" mean exactly?
I used my handy circut tester.

I hope this helps.

 

I would replace everything that looks damaged, melted, or scorched. Perhaps you just made a very bad connection with the wire nut, and this connection generated a lot of heat (although it doesn't seem that a radio would pull enough amps to cause much heat even with a very bad connection). Are you sure you understand the proper way to make a wire nut connection? If in doubt, read another book, or post back describing your technique. Or perhaps something was accidentally touching -- the bare wires are not exposed outside the wire nut I hope.

I still don't know why you had to use a pigtail. A simple wire nut is sufficient to connect two wires.

I also don't know what you mean when you say that the switch showed proper wiring when tested. If cable #2 was disconnected, there's not much to test at the switch. Are you talking about voltage tests, continuity tests, resistance tests, or amperage tests?

 

I went back and started over from the begining.
I tested the connections as I went. (making sure things worked as I connected them.)
Everything seems to be fine now. I think I made a bad connection or something was touching. Either way. It is fine now.

THe reason I used a pigtail is because there are 8 wires, not including the grounds, in this box. Without the pigtails, I would not have been able to fit everything. That is the way the instructions showed the fixture connected.

Thanks