Benefits of gfci and Afci redundancy in circuit

Question

I have read numerous times that having multiple GFCI/AFCI on the same circuit is a complete waste of money and really you just need the first outlet. But I have not seen any studies of redundancy of protection types in a circuit.

So my question is do false negatives not exist among GFCI/AFCI which might vary from GFCI/AFCI outlet to GFCI/AFCI outlet?

For instance increasing the number of outlets would decrease the possibility of a false negative in the complete circuit.

OR

Or do GFCI/AFCI not have false negatives in the sense I’m thinking but instead all only trip under the exact same thresholds/conditions which does not tend to vary from outlet to outlet through the position of upstream and downstream in the circuit?

Answer 1

Nuisance tripping or false tripping is a real thing in both devices for different reasons. nuisance tripping of GFCI’s is well documented and there are also issues with AFCI’s where they can’t tell it’s a dimmer or speed control and trip.

The reason you don’t see studies on redundant devices is because they affect each other and some devices self test will trip other devices and getting them all reset can be impossible.

I once was called to a home the owner tried to do exactly what you mention after hours of trying to rewire and get them to reset he called me. I told him he could have each receptacle as a line fed and not use the load but still may have some false tripping and finding the tripped receptacle would be easier but there would be no redundancy.

At that point with each point protected individually protected there would be more chance of failure because Electronic devices (both AFCI & GFCI) do fail. So in his case he went back to 1 per circuit.

This is the reason you won’t find studies on redundant devices and although I have not read the mfg instructions lately they used to identify this in there documentation that came with the device.