Series Fault

[marissa2]

Can someone explane to me what a series and a parallel fault is in respect to the AFCI requirement. Both myself and my coworker have a idea about it, but we are not sure if we are correct and would like to here from someone else about they think it is. Our idea about is a ground fault is a series fault, and a phase-to-phase is a parallel fault, or are we putting too much theory into it.

 

[winnie]

A series fault is one that is electrically in series with the normal load. For example, if you have a heavy load on a circuit, and a splice fails, you can still have current flowing to the load via an arcing connection at the splice.

A parallel fault is one that is electrically in parallel with the normal load, eg. a line-to-line or a line-to-ground fault is a parallel fault.

The danger of series faults is that the current through the fault is limited by the resistance of the load. The current through a series fault will never trip the OCPD on the circuit.

-Jon

 

[marissa2]

Thanks for that quick answer, it helps us alot.

 

[charlie b]

Good answer, Jon. That's one "attaboy" for you.

 

[don_resqcapt19]

The current through a series fault will never trip the OCPD on the circuit.

And AFCIs do not directly see series faults. They respond to this type of fault when the heat of the fault causes the "series fault" to become a parallel arcing fault, or a ground fault. If the cirucit has an EGC, the series fault will often soon become a ground fault and the GFP part of the AFCI will open the circuit.
Don