Knob and tube with AFCI

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dm9289

Industrial Maintenance Electrician
Location
Pennsylvania
Occupation
Industrial process repair/ maintenance Electrician
I recently worked on a 3 story very old towne house, the owner did it backwards having the walls over hung with new drywall and then painted it before calling an electrician. The house was almost exclusively knob and tube, I was able to run new receptacle circuits for the first floor and some of the second or third with minimal damage. Hoever changing the lighting circuits would involve substancial damage to his new drywall and the old knob and tube plugs on the 2nd & 3rd flr I did not eliminate due to the small amount of total receptacles on these floors and damage that would be caused by rewire. So I was going to try a couple safety measures and I wandered if anyone had any good or bad experience with these techniques.

1. Replace the remaining knob and tube receptacles with GFCI receptacles.

2. Place an AFCI breaker on the remaing lighting circuits just incase during the over walling or due to age of the wire there is any safety hazards.

Thanks for your input
Dave
 
Dave, I'm not a res. guy, but I don't think an AFCI could harm anything. By the way, I just

painted my car, do you do body work ? :)
 
hurk27 said:
the only problem with the K&T is if there is any shared neutrals, or bootlegged neutrals from other circuits, if so AFCI's will most likely trip.
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and in my experience, there could well be trouble from that or from some other partially abandoned wire.

Just finished a fire job The 80 yr old K&T wire insulation failed b/c the home was remodeled and additional insulation was added to the attic. This caused the wire to heat up in places where for years it was run in free air, granted, sometimes hot attic air. And I also think that those who added the insulation were not as careful as they could have been--I found places where pressures had been placed on the wiring, stressing it and compressing it, even shorting it out where it entered very old ceiling fixtures. It was in one of these fixtures that the homeowner first noticed the fire after having lived in the house for fifty years. For what it's worth, you are the one with the experience to inform your customer that this is a good time to take the safe option. Fires are never good to anyone.
 
Thanks for your advice and I loved the body work analagy , I am just looking for ways to keep this home as safe as possible given the circumstances
 
The AFCI device relies on its ground fault detection circuit for some it its work. You lose some of that when protecting knob and tube circuit because of the lack of an EGC.
 
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