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AFCI Breakers & Old Wiring

EdCY's picture

I know this topic has been discussed here before but I am looking for your current experience and opinion on the use of AFCI or combo AFCI/GFCI breakers with old wiring. My son bought a 1959 built house a couple of years ago. It has the NM 2 wire with thin ground wire that was in common use at that time. Previouse home owner installed a 100 amp Siemans panel but the old NM wire remains. Previouse owner(s) also did some ad-hoc remodeling, including some shaky electrical work. We have corrected junction box nightmares where visible and accessable. Most outlets are two prong but some have been changed to 3 prong grounded by using that thin ground wire.. My son has his first baby on the way! He has become paranoid about hidden wiring problems and wants to move to AFCI breakers for safety. I know this is code in new construction so there must be value in AFCI breakers. However, my reacent reading on AFCI doesn't inspire confidence in reliability or real protection. I would rather see time and resources spent on a qualified electrician checking the houses wiring for faults and installing GFCI outlets in the kitchen and baths where none exist today. But I don't want to be that guy who talked him out of AFCI breakers only to have some hidden junction in a wall cause a problem with my new grandchildren in the house.

Are AFCI breakers compatible and functional with this type of wiring? Do they really offer the level of protection as advertised? Can AFCI breakers be retrofitted in most existing electrical panels?

Your input is appreciated, thanks!


Both AFCIs and GFCIs can be (post #214998, reply #1 of 2)

Both AFCIs and GFCIs can be fitted to old wiring and will be effective at their primary tasks.  What can't be determined from this distance is how bad the existing wiring and to what extent it may need replacement.

I've seen a few claims that the advantages of AFCIs are oversold (especially in new, soundly-wired homes), though with old, flaky wiring they may be good insurance.

Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

There is nothing inherently (post #214998, reply #2 of 2)

There is nothing inherently wrong with the old NM and the 16ga grounding conductor. That is plenty of wire to trip a breaker in a fault. In fact with larger circuits the ground wire is downsized by the same proportion to the ungrounded conductors. It may be worthshile insuring any homeowner wiring was done in a professional manner and you should be adding the GFCI protections required in current code. That is a very mature technology and demonstrates a real safety benefit. AFCIs are getting better and will add additional protection also adding ground fault protection to the rest of your circuits at the 30ma level. The only question will be if there were some wiring practices that will trip an GFCI/AFCI (regrounded neutrals, shared neutrals etc). You might also find that old refrigerators trip GFCIs but that is usually pointing out small shorts inside the compressor.