Arc Fault trouble shooting

[Svndstin]

i work in california and we've just started installing arc fault breakers for bedrooms in compliance with new codes for our area..we've been having problems with the breakers tripping. whenever anything is plugged into any plug on the arc fault circuit, the the breaker instantly trips. each circuit has it's own neutral (i.e. we're not using 12/3), the grounds are seperated from the neutrals. if we replace the AFCI with a normal breaker, or a GFCI breaker, everthing works fine. do you have any advice?

 

[George Stolz]

Re: Arc Fault trouble shooting

I am dubious that a GFI breaker would work if an AFCI was tripping.

Generally, you have two problems causing an AFCI to trip (in an uninhabited, brand new house).

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• <font size="2" face="Verdana, Helvetica, sans-serif">Ground wire touching a neutral screw in a receptacle in the AFCI circuit</font>
• <font size="2" face="Verdana, Helvetica, sans-serif">Neutrals tied together in a multigang switchbox including a switch from a AFCI circuit</font>

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Generally, the reason the AFCI trips is because of the 50ma ground fault protection inside the device not getting back all the current on the neutral that it's putting out on the hot. So it trips.

Go to the panel. Turn off the circuit. Remove the load-side neutral (white wire of HR) from breaker. Test for continuity from this disconnected neutral and the neutral buss. I'll bet it confirms my theory.

 

[tonyi]

Let me add...

There are some older fixtures that have the housing strapped to the neutral rather than using a seperate gnd. If mounted in a metal box, these things are essentially a hardwired bootleg guaranteed to trip an AFCI or GFCI.