Arc fault breaker

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Albuquerque nm
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I installed a new subpanel and the arcfault trips with out a load connected.
I turned off everything in main panel and tried it and again it instantly trips with no load

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LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Welcome to the forum.

If it even trips with no wires attached to the breaker, it must be defective.

The incoming voltages are correct, right?
 

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
With the load neutral disconnected, and the breaker off, check for continuity between the load neutral and ground. I believe you will find that it will show continuity. Probably a ground wire touching the neutral terminal in an outlet somewhere. Divide and conquer. Break the circuit in the middle, check for continuity again. Keep dividing until you locate the fault.
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
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Semi-Retired Electrician
It doesn't make sense since grounds and neutrals are together in main panel

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That's before the Arc fault breaker. On some brands there is a form of GFCI protection in them and you can't have neutrals and grounds touching past/downstream of the breaker or it will not set. In other words, treat it like they are GFCI and wire accordingly.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Have you checked both L-N voltages yet? Try it with loads on standard breakers.

Try the tripping AFCI breakers in the main panel temporarily, if they'll fit.
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
I installed a new subpanel and the arcfault trips with out a load connected.

You mean it trips with your wiring removed from it? Breaker sitting in the panel all by itself disconnected? It trips as soon as you apply power to the sub-panel by turning on the breaker in the main panel that feeds it? Two of the same breakers in the sub-panel, only one does this?

What happens if you swap the breakers or move the one that trips to another slot?

Does anyone know if the service neutral from
Co op could cause thus its a 200 amp underground service .

Never heard of that. Can't see how.

thought it was the breaker and tried a new one.

Beginning to think you got a couple of bad breakers. Were they both from the same supply house at the same time?


-Hal
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Semi-Retired Electrician
I turned everything off on main panel leaving only the subpanel on .there are only 2 breakers in sub both arcfaults it still trips Instantly

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All though possible, I don't think both breakers are bad. You say there is only two AFCI breakers in the sub with no other breakers. You're going to have to go to each circuit and look at each device (receptacle, switch, lights, etc.) and see if there are any ground to neutral faults. With both breakers tripping, it sounds like the neutrals may be crossed or mixed up somewhere along the line. This most often happens in a multigang switch box.
You can take a short cut on test by doing as was said and replace the breakers with GFCI temporarily. If they trip, it shows that it is a ground to neutral fault. Then proceed in taking things apart.
 
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