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One of my circuit breaker trips instantly.

I try to reset it but it trips immediately and trips the breaker under it too.

I can reset the break next to it and it is fine until I try to reset the problem breaker again.

Could the breaker itself be bad? and if so could I swap it out myself?

How would I find which outlets, light, fans are powered by this possibly bad breaker?

Update: I added a video showing the exact issue.


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Did you make any changes to the electrical system that caused the breaker to trip? If you follow the wire terminated at each breaker (the "bad" one and the one below), are the wires part of the same cable (you may have to remove the panel cover to determine this, do so with care)? Do the two breakers look like they are somehow connected? –  Tester101 Oct 3 '13 at 16:50
The breaker might be bad, and you might be able to change it yourself. As for figuring out which receptacles, lights and fans are fed through the breaker. That's easy. It's all the things that stop working when the breaker is OFF. –  Tester101 Oct 3 '13 at 16:53
Do the wires connected to both of those breakers go out to the same cable/conduit? –  BlueRaja - Danny Pflughoeft Oct 3 '13 at 18:11
Spending way too much time in my attic this summer redoing some electric I noticed a junction box that had three different circuits in it. One dead-ended there, one was for some lighting and traveled on, and another for kitchen stuff that traveled on. The hots for two of the circuits were laying on top of each other. They were in a proper nut but if they came out we have your situation. –  DMoore Oct 7 '13 at 15:19
Assuming that B1 is the top breaker and B2 is the bottom breaker, what happens when B2 is off and B1 is turned on. You've shown what happens when B1 is turned on when B2 is on, but not when it is off. –  2 Left Thumbs Nov 7 '13 at 13:36
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4 Answers

Somewhere in the circuit there is likely a low resistance connection between the two legs. The most likely culprit would be a split duplex receptacle that was replaced, and the tab between the upper and lower sections were not removed. Another likely cause would be a staple, nail, screw, etc., that penetrates both cables.

With both breakers off, check continuity between the ungrounded (hot) conductors of each circuit.

  • Turn off both breakers.
  • Set your multimeter to continuity mode, or the lowest resistance setting.
  • Touch one probe to the lug of one breaker, and the other probe to the lug of the other breaker.

With the breakers in the off position, you should read infinity (or open). If you get a reading, it means that these two conductors are connected somewhere. If the reading in not close to 0, there could be a 240 volt load connected between the legs. If the reading is near 0, you have a low resistance short between the legs.

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You have a back feed from one circuit to the other. It would appear power is leaving from one circuit breaker and somehow finding its way back to the panel on a different circuit. Consider back tracking any areas where electrical work was done. Maybe a junction box where both circuits meet for some reason. If all wires tied together, that would create a back feed. Again, if any work has been performed recently, I would look there first. Separate the wires and attempt to turn both circuits on. If the circuit stays on, you would more than likely have both hots there and have 240 volts as well.

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Can you pop the cover of the main panel? It is impossible to tell without more info, but what could be happening is someone wired a 240V appliance (requiring a double breaker) to two individual breakers. If there is a problem in one of the circuits, it could be tripping both breakers. Alternatively, as others have mentioned, black wires from both breakers are touching somewhere (either in the panel or somewhere else). In either case, removing the panel cover should give you more info

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The video shows clearly that B1 and B2 are somehow interconnected. Figuring out how is the trick.

Step one is to determine what exactly B1 and B2 control. You could gain some help from a tracer tool such as the Klein ET300, but really a lamp works just as well.

  • Make a list of every outlet and light affected by these breakers, post this data. Unplug everything.
  • Turn off the main, remove the panel cover and post some pictures.
  • Now turn the main on, and B1 off. Measure the voltage on the black terminal? Hot or not?
  • Now turn the main on, and B2 off. Measure the voltage on the black terminal? Hot or not?
  • You can swap the two breakers if you like to eliminate the chance that B2 is defective.

An electrician would likely brute force finding the problem. The only other tool I can think of that would help is a line length tester, which can give you a reading in meters for the length of a cable to a resistance point. But the tool is too exotic and might not even work in your case.

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