Why has one circuit lost power?

Question

About 2 days ago we noticed that a 20 amp (single pole) circuit breaker was tripped. Ok not a big deal, it's doing it's job. Then I noticed that the breaker was tripping even with a single light on. Then it finally came to an end, I was unable to get the breaker to stay in the "on" position at all it would immediately trip.

At this point I thought ok the breaker was pretty old, had never tripped itself before now it's constantly being tripped. I do have some experience with home electrical systems. I have installed several breakers in existing boxes before when I had a job working HVAC. Anyway I thought that there was a possibility that the breaker had went bad, so off I go to get a replacement.

Now here's where I am getting into my real problems--the wire that was and still needs to be connected to the new breaker to finish the circuit and say yay it's been fixed now and possibly is the main cause of all of the issues has no power!! It is essentially a dead line. I found this out when everything was connected back together and honestly better than it was flip the breaker on and immediate trip!!!

How do I find where the dead wire goes and what are possibilities of why it has zero power coming through it.

Answer 1

Simply put, you have a true short in the cabling someplace. To solve your problem: First of all be sure you are working with the affected outlets and fixtures and don't accidentally pull something out that is still powered up. Then you should pull out all the affected outlets and fixtures and look for any shorts. If none found, take pictures of each one BEFORE. Then disconnect everything including the connection to the breaker. Be sure that you aren't testing anything live by testing for voltage first. Then start testing with a DMM on the ohm setting. You should have near infinite resistance across the white and black in every case. If you find a short (very little resistance), you should be able to find the "other end" of the cable because there should be another pair with low resistance. Then, hooray, you found the cable with the short. What you do from there depends completely on where that cable runs, hopefully not to difficult a replacement. It would be good though, to identify the cause of the short. It's very unusual for the cable itself to be compromised.

But rodent damage can do it: I had a similar situation in my previous house. Some outlets and lights stopped working and another circuit started tripping breakers with nothing plugged into it. The affected outlets were on a wall shared with an attached garage. So I started pulling off sheetrock and this is what I found!