New AFCI breaker tripping.

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  #1  
Old 12-15-15, 01:37 PM
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New AFCI breaker tripping.

So my wife wanted me to install new AFCI breakers in our bedrooms. A good idea to prevent a fire so I installed about 5 AFCI breakers for the outlets in each bedroom. All but one circuit (guest bedroom) is working great. On this circuit, if there is any load it instantly trips. If there is nothing plugged in it will trip after about 8 hours.

My Panel is Square D QO. The wiring has been there since the house was built in 1970. Panel is in a basement with drop down ceiling and the guest bedroom is on mainfloor. I followed the wire to where i believe it goes up into the wall to the first of 3 outlets on the circuit. There is only 3 feet of wire I cannot see between the panel and the first j-box outlet. Another wire follows this wire and goes up into the wall with it.

My troubleshooting so far:
1) I swapped an AFCI breaker on a good working circuit for the one on the guest bedroom circuit not working. I determined the breaker is fine.

2) I opened up the first junction box (outlet) on the circuit. I disconnected the wire going to the other outlets (capped them) and tried running a light on just that one outlet on the circuit. The breaker still tripped instantly like always.

3)I tried using the troubleshooting instructions in the manual and held down the test button in the breaker while turning the breaker on. It trips instantly telling me that it must be either a Arcing to Ground Fault, Shared Neutral, Grounded Neutral, or Ground Fault.

Any help would be appreciated. I have a fresh paint job and don't feel like cutting into drywall unless until i have made sure it is not something else. Thanks.
 
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  #2  
Old 12-15-15, 01:53 PM
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Sounds like a legitimate fault.

Make sure that you're really testing at the first device on the circuit. Sometimes a circuit goes through a light switch or light fixture box you might not be thinking of.

Do you have a multimeter to do some testing? You'll want to completely disconnect the wires on the receptacle side and the main panel side. Measure resistance between black-white, white-bare, and bare-black. You should have infinite resistance on these measurements. If you get a resistance measurement, you have a damaged cable somewhere.
 
  #3  
Old 12-15-15, 03:46 PM
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All it takes is one loose connection.
If the outlets are back stabbed change them to under the screws.
 
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Old 12-15-15, 04:02 PM
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hmm

I am 99% sure I have the first box in the circuit. If I do not then the electrician was an idiot for wasting that much wire. I have seen stupider stuff in my house though.

I just replaced the receptacles on this circuit as well, they are all properly using the screw terminals. No back-stabs. There is not a nick in a wire that I can see.

I do have a multimeter, although testing ohms is not my expertise. Let me rephrase what I think you want me to do. With only the first junction box connected, go to the panel and disconnect the wire on the faulty circuit at the breaker. Set the Multi-meter to 2000 Ohms and see if it reads 0?

I was able to easily do this to the wire going to the other receptacles and it read 77 Ohms. Will there be resistance from the receptacle? do I need to disconnect the wires at the receptacle and wire nut them together to test it right?
 
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Old 12-15-15, 05:02 PM
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On this circuit, if there is any load it instantly trips. If there is nothing plugged in it will trip after about 8 hours.
Ok.... that tells us you don't have a direct short.

My guess is you have a leak to ground from the neutral. With an arc fault breaker.... neutral cannot touch ground after the breaker.

You will need to remove the white wire from the breaker and check it to ground. There should be no continuity.... no reading.
You can also remove the black wire from the breaker. There should be no continuity from it to ground either. Most likely there won't be.

Leaving the wires out of the breaker and making sure there is no device plugged in or connected to the circuit..... check for white to ground and black to ground. There should be no continuity anywhere in the circuit.

If you have a settable meter..... make sure it's set to the highest ohms reading for this test.
 
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Old 12-15-15, 05:24 PM
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The wiring has been there since the house was built in 1970
I don't suppose this is aluminum wiring.....is it?
 
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Old 12-15-15, 05:52 PM
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No, it is copper wiring. Good ole 12-2. However it is old enough the outer sheathing isn't great. I'll post back after I have disconnected from breaker and checked resistance. Largest setting on my multimeter is 2000k Ohms.
 
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Old 12-15-15, 06:15 PM
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2000k is fine for this test.
 
  #9  
Old 12-15-15, 06:34 PM
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Is this a new dual purpose GFCI/AFCI breaker?
 
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Old 12-15-15, 08:00 PM
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I agree with PJ, sounds like a neutral to ground short.
 
  #11  
Old 12-15-15, 08:18 PM
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Solved

Thank you for the help. I disconnected the the wires at the first j-box and wire nutted them together. Then disconnected them at the panel and tested resistance to find that black and white had NO continuity. So, I checked white to ground, no continuity. I checked black to ground and no continuity. I then realized, the only possible explanation for this was I installed the wrong neutral. Turns out that was exactly the case. I followed the wire to in the panel to find the right one and now everything is working great. Thank you for all your help.
 
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Old 12-15-15, 08:21 PM
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This is actually just an AFCI breaker. However, from what I understand most AFCI breakers have a GFCI functionality except they don't prevent small enough ground faults to qualify to have a GFCI label.
 
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Old 12-16-15, 12:58 AM
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Glad you got the problem taken care of.
 
  #14  
Old 12-16-15, 05:15 AM
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Only some afci breakers contain the gfi component.
 
  #15  
Old 12-16-15, 12:32 PM
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This is actually just an AFCI breaker. However, from what I understand most AFCI breakers have a GFCI functionality except they don't prevent small enough ground faults to qualify to have a GFCI label.
I believe what you are referring to is 30 mA GFCI function which isn't adequate for personnel protection which is 4-6 mA.
 
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