I am upgrading a handful of breakers - a couple of circuits with lighting need CAFCI and two with outlets need GFCI (I am going with dual function breakers rather than GFCI outlets).

I have two lighting circuits that by code require arc fault protection but do not require GFCI. Would it be a problem to use a dual function breaker instead of a CAFCI breaker for those circuits?

It seems that DF are usually more expensive than CAFCI, which is a reason one wouldn't normally do what I am asking, but I happen to have a couple of extra DF breakers sitting around, and I would rather use them than have to purchase new CAFCIs.

  • Remember, code is typically the minimum acceptable safety level... nothing wrong with going above and beyond! Harper's answer does raise a great point though--keep convenience in mind! If your breaker panel is easily accessible (mine is on the kitchen wall, for example), it may not be a big deal. If you're in a long ranch-style house and it's in the garage at one end of the house, and you're in the other end doing something that causes the GFCI part to trip, that's gonna get old fast.
    – TylerH
    Oct 4 at 21:10

There's no downside to over-protecting a circuit beyond cost. So having GFCI on a circuit that isn't required to have it isn't an issue. You're more likely to have an arc fault on a lighting circuit anyways (halogen flood blew on one I had installed and the CAFCI registered it as an arc fault).

The only place an unneeded GFCI does become an issue would be some types of mission-critical circuits, like for a refrigerator.

  • Or, IIRC, a fire alarm control panel. Oct 4 at 14:02
  • 3
    Your mission, should you choose to accept it, is to find something tasty in the fridge to eat...
    – TylerH
    Oct 4 at 21:11
  • 1
    Are nuisance trips that common? I'm in NL where all circuits MUST be protected a (30mA) CFCI breaker, the only exception is for hard-wired appliances on a single circuit. In the 10 years I live in my place I have never had any breaker trip on me.
    – Pelle
    Oct 5 at 7:21
  • @pelle in north america, GFCIs are usually designed to trip at 6mA fault current. So it can happen more easily. They also sometimes cause false trips as they age, though that doesn't seem to be as much of a problem in more modern ones so far. It's not an every day occurrence, but false trips do happen sometimes.
    – Grant
    Oct 5 at 15:19
  • Incidentally, it used to be the case that the circuit hosting smoke detectors was debatable whether it should be detected or not, but now the debate is meaningless because smoke detectors have long-term batteries.
    – Joshua
    Oct 5 at 19:07

It would give you more protection than maybe you want.

The trouble with installing safety systems, is the darn things go off on you. And then, you have to deal with the problem. Safety is always better if you do that, but it holds your feet to the fire and makes you fix any problems on its timetable, not yours. Because the circuit will not work until you do.

  • How likely do you think it is that lighting circuits will nuisance trip with a DF where they wouldn't do so with arc fault breaker alone? Is this just theoretically possible, or is it something that is actually common? Oct 5 at 12:41

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