Can a dual function (AFCI+GFCI) work on a circuit which has only 2 wires in a cable - no bare ground wire

[Curiousv]

This is old house with newer panel (panel is installed in 2010 I think)
Most of the circuits have only 2 wires in the sheathed cable - no bare ground wire in it.

So someone has installed GFCI outlets - 1st in line in all circuits
Now we are thinking of replacing those std breakers to newer dual function breaker
What will happen - will it trip because it has no ground wire or it will work?

@jadnashua @Reach4 @Tuttles Revenge

 

[wwhitney]

Neither GFCI nor AFCI requires an EGC to function.

Cheers, Wayne

 

[Sponsor]

 

[Afjes]

Any circuit which is presently being protected by a GFCI receptacle really should not also have a GFCI breaker. Sometimes this causes phantom tripping which can be a bit of a pain.

What you can do is purchase only AFCI breakers. These will give you the arc fault protection of the dual function and since you have GFCI receptacles protecting your circuits then no need for the GFCI function on the breaker. You would just be spending more money.

You say:

"So someone has installed GFCI outlets - 1st in line in all circuits"

Since the present GFCI receptacles are wired "Load" to protect downstream then you are fine - however anything before that first receptacle is not protected such as the wiring back to the panel.

If you choose to use the dual function then I would highly suggest you replace the GFCI receptacles with regular receptacles. It really is no danger just may be an inconvenience in tripping and really should not be double protected.

 

[wwhitney]

Any circuit which is presently being protected by a GFCI receptacle really should not also have a GFCI breaker. Sometimes this causes phantom tripping which can be a bit of a pain.

Having GFCIs in series doesn't cause nuisance tripping to my understanding. It just means that in the case of excess leakage current downstream of both GFCIs, either or both GCFIs may trip, and the behavior may vary each time.

Cheers, Wayne

 

[Reach4]

An alternative to cascading the GFCIs is to use a GFCI at each outlet. This presumes the boxes are big enough. The advantage is that a fault in one place does not take all of the outlets out of action. You will be able to figure out which outlet has the fault that causes the tripping. If you are not getting troublesome tripping, I would just leave it as is.

This of course does not protect the wiring on the way to the outlets from arcing type faults.