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I opened up a junction box to reconfigure two switches.

I turned the breaker off and unscrewed one switch and all of its wires.

The hot, neutral and ground were separated so they wouldn't touch.
I turned on the breaker and I used a non-contact tested to touch the the hot wire. I somehow pushed it down and it touched the junction box and welded itself to the box. However, the breaker didn't trip. I had to turn it off myself.

I looked in the box and the box is not grounded. Is that the reason why the circuit breaker didn't trip?


This is what the box looks like. junction box not grounded


After grounding the box grounded box

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    That box is grounded somehow. A hot touching ungrounded stuff acts the same as being in the air. Some panels/breakers are known to be bad and do not trip. A picture of the panel and labels will help.
    – crip659
    Commented Apr 22 at 10:42
  • I think the box was loosely grounded because some of the loose ground wires are touching the box!
    – milesmeow
    Commented Apr 23 at 17:46
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    If that's the wiring and there are two switches in the box, there is no neutral - those would both be switch loops with hot whites. If they were done properly when switch loops were legal, anyway. If improperly wired the blacks might be hot. Grounding the box is required - join both of those wires and connect them to the box with a 10-32 screw.
    – Ecnerwal
    Commented Apr 23 at 17:52
  • @Ecnerwal Thank you. Didn't even occur to me that there's no neutral. I've grounded the box... I've updated the post.
    – milesmeow
    Commented Apr 23 at 18:02
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    Metal touching metal is usually enough to make contact, it might not be a good contact, but good enough the weld a wire. A screw holding a wire on is for very good contact that will work all the time.
    – crip659
    Commented Apr 23 at 19:24

1 Answer 1

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If the box was fully ungrounded, the hot would not have welded itself to the box. So there is (or at least was) some connection to ground or neutral there.

So, there's a weak connection somewhere that is limiting the current (or as speculated in a comment you have faulty breakers, but given the house didn't catch fire while you were managing to get the breaker turned off I'd bet on a faulty connection and a functioning breaker over a faulty breaker, without further information.)

Could be a loose wirenut. Could be loose grounding screw. Depending on wire type, could be stranded wire where only a few strands were actually connected and they burned through like a fuse.

Or there could be a GFCI on this circuit which tripped before the breaker did. It is not clear if you've tried to power it back on after clearing the fault. You might not notice the GFCI (or AFCI) being in play until you turn the breaker back on and find you still have no power.

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  • I added a photo of what the inside of the junction box looks like. The grounds from the romex cables are touching the box...so that's probably loosely grounding the box.
    – milesmeow
    Commented Apr 23 at 17:47
  • Do you think it was the loose ground wire that allowed the hot to weld itself to the box?
    – milesmeow
    Commented Apr 23 at 18:05
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    Would have to be, as per the first sentence (or 3 paragraphs) of my answer, unless there was some other ground connection, which seems unlikely.
    – Ecnerwal
    Commented Apr 23 at 18:16

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