circuit breaker tripping

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  #1  
Old 01-27-06, 08:55 AM
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circuit breaker tripping

I have a circuit breaker that has tripped. There are 2 switches? on one breaker, only 1 tripped off. Anyway, replaced the breaker no help. Unplugged all appliances and turned off all light swithes on circuit, no help still tripped as soon as I turned on the main breaker. How do I find where the problem lies? Not really an electrian so in laymans terms please.
 

Last edited by richirene; 01-27-06 at 09:16 AM.
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  #2  
Old 01-27-06, 09:19 AM
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Rich, since you have everything off the circuit and switches off and the breaker is still tripping on reset you most likely have a hot wire touching ground or neutral in one of the receptacle or switch boxes. You need to identify every outlet or switch box on the circuit and start looking in them for any bare wires touching each other or wires that have come out of a wirenut and are touching a bare ground wire etc...

The breaker is called a tandem breaker where two breakers are designed into one case and are used in many situations to increase the number of circuits one can operate out of a crowded panel.
 
  #3  
Old 01-27-06, 10:04 AM
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Could I just start by unhooking all wires that connect to one unworking recepticle (would this break the circuit loop?) and then try resetting the breaker to see if it stays on if not, go on to another unworking recepticle and so on to find out which one is bad. Maybe this will save time and I will get lucky and find the bad one on the first or second try? If so, should I start with one that is closest to the breaker box?
 
  #4  
Old 01-27-06, 10:20 AM
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You've got the right idea. First, "Map out" everything on the circuit - see what's not working with that breaker off. The circuit will normally be wired from the panel out, so you can assume that the devices closest to the panel will be the first ones wired. Go to a receptacle that's about halfway out on the circuit and disconnect one of the black wires from the receptacle (I'm assuming that you have two 3-wire cables with black / white / bare ground(one feed in and one feed out). You only need to disconnect one of the wires, becuase that will effectively "break" the "live" wire in the circuit. Try turning on the breaker. If it holds, you know your problem is in the second "half" of the circuit. If not, the problem is closer to the panel. Go halfway into the offending section and repeat the procedure. Examine all wiring and devices carefully. When you find the problem, there should be sign of a short circuit (arc marks, discoloration, smell, etc.)

If possible, trace the circuit wiring where it is exposed (i.e. under the house). You may be able to see it running under the house and disappearing up into the walls where the devices are. That will help you to see exactly how the circuit wiring has been run. Also, it's always possible that there could be a short circuit in the wiring or a junction box under the house or in an attic.
 
  #5  
Old 01-27-06, 10:34 AM
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Things to think about

What about switched receptacles?

What about pigtails?

Might also be switch loops where power is in the light fixture.
 

Last edited by Roger; 01-27-06 at 04:13 PM.
  #6  
Old 01-27-06, 10:41 AM
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Thanks, I will try this and get back to you. One question though How do I know which one is feeding in and which one is feeding out? Or does it matter just unhook one of the black wires?
 
  #7  
Old 01-27-06, 11:00 AM
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Roger, I answered your questions in my earlier post. Halfway out is halfway along the circuit between the panel and the last device on the circuit. The hypothetical I described doesn't involve pigtails or switched receptacles - I described the most common situation that's encountered which is one cable coming in to a box and one leaving. If he happens to open a box with one cable coming in and two leaving, then I suggest he examine the contents of the box for signs of a short circuit, and then if everything looks good, move on to an adjacent box with only two cables instead of breaking the joint in the three cable box.

Richirene, it doesn't matter which is the hot wire in the situation I described earlier. If you want to know, measure for voltage between the two blacks and the ground. One will be live. Of course, it you do find one to be live, it means that the breaker didn't trip, and the problem lies farther out on the circuit. And to address Roger's point, farther out doesn't necessarily mean farther away from the panel. If the circuit runs down one side of the house, away from the panel, and then returns down the other side of the house back towards the panel, the receptacle "farthest out" could conceivably be closest to the panel. That is why I suggested you try and visually locate the circuit wiring under the house or in the attic if at all possible. Most of the time, however, the farther you get from the panel, the farther along the circuit the device will be (relatively).
 
  #8  
Old 01-27-06, 11:21 AM
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I did not mean to sound disrepectful.
 

Last edited by Roger; 01-27-06 at 04:14 PM.
  #9  
Old 01-27-06, 12:15 PM
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Some mechanics are "parts changers" and some are troubleshooters. Parts changers start changing parts and continue doing so until they "fix" the problem. Blindly pulling devices is akin to parts changing. If you're lucky, the problem will be in first device you pull out of the wall. If not, it will be the last. If you can eliminate half or more of the devices from the equation, your odds of successly finding the fault are increased.

I was a service call electrician for 10 years and I used the "scientific" method that I described earlier. I've wired and rewired 50-100 houses in my day. As a general rule, the closest device to the panel is the first on the circuit. Reasonable inferences about how the circuit wiring runs can reasonably be made by looking at the physical location of the devices. There are always exceptions - I'm not denying that, but since the problem owner is going to have pull devices to locate the short, what's the harm of making an educated assumption to figure out where to start.

Say you go to a device located halfway between the closest and farthest device and break the circuit at that point. The breaker holds and you know the problem is farther down the line. What I failed to mention earlier is that with the breaker on, all devices should be checked for power. Any that are live can be eliminated from consideration, which might be half the circuit. The next step is to repeat the procedure using the remaining devices that were not live - find the halfway point and repeat the test. If the breaker holds, determine what devices are left and the possibilities are reduced further.

The other option is to just start closest to the panel and start removing and inspecting devices and just hope you find something before you get to the last device. Of course, if the problem is underneath the house, in the attic, or in a wire that has a picture hanger nailed through it you'll never find the problem with that method.
 
  #10  
Old 01-27-06, 12:37 PM
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I did not mean to cause argument.

Sorry I created the problem, my mistake.
 

Last edited by Roger; 01-27-06 at 04:09 PM.
  #11  
Old 01-27-06, 01:11 PM
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O.k. I disconnected the negative power to one device half way down. I now have power to the first half. My question is do I RECONNECT the negative before going to the next device in question?
Also, I want to thank you this has been very helpful.
 
  #12  
Old 01-27-06, 01:16 PM
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Yes, but before you do, check to see which devices (lights and receptacles) can be eliminated from consideration. Then turn the breaker off and replace the black wire. Move down halfway through the devices that were off when your breaker held, and repeat. You know the problem isn't between the panel and the device you pulled.
 
  #13  
Old 01-27-06, 01:42 PM
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The term "negative power" means nothing. There is no positive and negative when discussing alternating current, as the hot lead is both positive AND negative.

If you have determined that the problem is in the second half of your circuit then you need to remake the connection you broke and then break the connection in somewhere in the second half of the circuit for your next test.
 
  #14  
Old 01-27-06, 02:13 PM
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Originally Posted by richirene
I disconnected the negative power
With automotive (direct current) you have negative voltage which is grounded and positive which is ungrounded.

But don't mix up black and white when working on house wiring!

With properly installed 120 VAC, in the USA white is grounded (unless otherwise marked), black is always ungrounded -- the opposite of automotive.

60 Hz alternating current means that it alternates from positive to negative and back 60 times per second.
 
  #15  
Old 01-27-06, 02:53 PM
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Originally Posted by bolide
With automotive (direct current) you have negative voltage which is grounded and positive which is ungrounded.
Careful bolide, there are direct current setups that have negative voltages. Computers, for example, have positive 12 volts, positive 5 volts, negative 5 volts and negative 12 volts. Laptops have other voltages.
 
  #16  
Old 01-27-06, 04:39 PM
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Originally Posted by racraft
Careful, bolide
About what?


there are direct current setups that have negative voltages. Computers, for example, have positive 12 volts, positive 5 volts, negative 5 volts and negative 12 volts. Laptops have other voltages.
I didn't say a word about them.

There are numerous direct current applications.

There are ungrounded AC applications.

I was contrasting exactly two electrical systems (modern 12VDC automotive and USA 120VAC household) with which the poster might be familiar.
My remarks cannot be extended to any other of the thousands of electrical systems that exist in the world.

richirene's wording "I disconnected the negative power" is not something that we say when talking about computers. That terminology suggests (but does not prove) that the speaker is familiar with 12VDC automotive electrical systems.

My caution to him is that he not bring preconceived notions from automotive electrical systems over to household 120/240VAC systems.

Of course automobiles also have AC electrical.
So I specified that I was talking about only the direct current portion of automotive electrical systems.

I assure you that the author never intended that the reader would construe his remark to mean that automotive is the only direct current electrical system in the universe. The remark inside parentheses can be deleted without altering the meaning of the statement.
 
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