AFCI Breaker wont reset

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mxlplx00

mxlplx00

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Location
Watsonville, California
Occupation
Electrician
Hi,
I did a small service change and put in a 100 amp Square D Homeline and AFCI breakers. I've been using these a lot now and never had a problem but I may have messed this one up and want to check with someone.

I rang out the house really well and everything looked fine. I put AFCI for all living areas. The kitchen is still in rough in so I now have 2 - AFCI 20 amp Single pole (Receptacles), a double pole 20 amp (AFCI) for a 3 wire (receptacles) and 1 - 15 amp for lights. Everything was running fine for a few weeks but today they called me back to pull the service off the wall to add some plywood.

There is a main in another building and I had it off to work on my panel. Half way through they asked me to turn it on for 5 minutes. I did but forgot to re-connect the neutral feeder that I had removed to get to a screw. When I noticed I turned off the main again and then noticed that 2 AFCI (on the same phase of the buss) had tripped. I fixing the neutral but now the 2 breakers wont re-set. So I guess that I smoked them, right?

I mean, they weren't on opposite buses sharing a neutral. They are on the same phase with dedicated neutrals. Also one is a 15 amp for all the lighting (#14 wire) and the other a 20 amp for receptacles (#12) and in my inspection I did not see and lighting circuits in boxes with receptacles. So I'm saying I don't see how 240 volt could feed through when the neutral was missing like this. Are these thing this easy to smoke of did I make a fatal error (LOL)?

Thanks
Marc
 
Are you sure they are on the same leg/phase?
Are the breakers with a pigtail neutral or plug-on neutral?
If pigtail, is it connected to the neutral bus and circuit/load neutral to the breaker?
Did you try to take the load wire off the breaker and try to reset it then?

If answer is yes to the last 2 questions, I would try a new or different breaker that you know is working.

Why are you adding AFCI breakers if you're just doing a service change?
 
mxlplx00 said:
So I'm saying I don't see how 240 volt could feed through when the neutral was missing like this. ?
Click to expand...


The voltage on that phase probably wasn't 240 V but it probably was a bit more than 120 V ( say in the 150-160V range or higher).

I really don't know how much of a power surge an AFCI can stand but we can be sure it was subjected to a voltage over 120 V.

In a way you got lucky because a lot of valuable equipment could have been damaged.
 
mxlplx00 said:
forgot to re-connect the neutral feeder that I had removed to get to a screw. When I noticed I turned off the main again and then noticed that 2 AFCI (on the same phase of the buss) had tripped.
Click to expand...
Hi Marc,

With the feeder neutral disconnected, the neutral bar and connected branch circuit neutral conductors become "unstuck" to zero volts. Rather, depending upon the summed resistance of the running loads on one panel buss bar, compared to the summed resistance of the running loads on the other panel buss bar, the division of the 240 Volts, buss bar to neutral to buss bar, will shift proportionately. One side will go higher, while the other goes lower

The buss bar that the AFCIs (that won't reset) are connected to is the buss that had the higher voltage. Any solid state devices connected to that buss, devices that keep a portion of their electronics always on, will have experienced the higher voltage. An individual device's internal protective circuitry, that may, or may not, be there, determines whether there will be damage. Solid state devices, unprotected, can be damaged by voltages as low as 135 V.

You know which buss got the high voltage by the location of the damaged AFCIs.
 
Yes (L. Bill), I took the field wiring off the breakers and they still wont re-set and they are plug-on neutral not pig tail.

After sleeping on it I see now that even though the neutrals are not shared or crossed (hopefully) in the field that all the circuits share on the neutral bar and would find a complete path between the 2 hot legs through the field devices there. And though I didn't smell smoke I now believe I spiked them and they are dust.

I now rightfully deserve the electrical bonehead award. :)

Thanks for the help guys.
 
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