ELA
Senior Member
- Occupation
- Electrical Test Engineer
The hot wire run without the neutral increases its inductance more than if run with the neutral together.
The higher freq. signals of interest to an AFCI require more inductance to filter effectively. Capacitance is more effective as a filter as the freq. gets much higher.
Running a longer romex (conductors together) is likely to be less effective, to a point. As the romex length increases it increases both inductance and capacitance. At some point it will attenuate and mask the offender (whether that be a tread mill, or a true arc).
Has anyone ever seen a specification for the maximum amount of cable run that can be used on a AFCI circuit? I think there should be one. Of course there are numerous other variables including the type of loads used on the circuit.
The reason I recommend an EMI filter at the offending load is because it is most likely to prevent a false trip but still leave the remainder of the circuit run mostly "unmasked".
Adding a coil(filter) at the head of the circuit is more likely to mask the entire circuit.
A good EMI filter will have an inductance much higher that a simple 6ft run of a single conductor.
I feel it is totally unfair for an electrician to have to explain to a customer why an AFCI is such a good thing, even though they may false trip and be a nuisance some of the time.
While the GFCI was more nuisance trip prone in its infancy, and evolved, the AFCI is attempting a much more complex function.
If they want AFCIs to totally succeed there would have to be standards applied to all possible loads to assure compatibility with AFCIs. Not sure how or when that could/should ever happen?
How unjust to force their use without addressing all the legacy appliances and equipment that may (look like an arc under normal operating conditions).
