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I know that properly working and regularly tested AFCI breakers are great for safety. But do they mitigate all safety risks imposed by knob-and-tube? If not, what safety risks remain?

For reference: our bedrooms and bathrooms have K&T. We don't use any high amperage devices in those rooms (absolutely no vacuums, gaming PCs, hair dryers, etc.) We're also not ready to chuck the money for a full rewiring quite yet.

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"othering" is fun. That's where you identify a group as "Bad", and pretend all others are "not bad".

It's a little too easy to say "Knob & Tube = bad". They require AFCI on new construction, which isn't Knob & Tube, and isn't aluminum wires improperly placed on copper-only terminals and mistorqued. It's mandated because brand new wiring - the stuff you plan to replace the K&T with - is on the same footing as K&T, really. It fails too.

So yes -- AFCI breakers help, and will protect against arcing on any wiring. (The only place I don't see AFCI as useful is inside metal conduit, and it's always useful in bedrooms due to electric blankets.)

I would say GFCI helps more, because knob-n-tube usually means "no grounding". GFCI removes the human-safety risks from lack of grounding.

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  • I'd use "dufies" (dual function) breakers. Actually do 4 things: They have both types of arc fault protection, ground fault protection and over-current protection. Not all K&T wiring is bad, some of it was real craftsmanship. But for the most part, it's best to be rid of it eventually. Commented Dec 18, 2021 at 18:16
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    So, with a properly rated, properly functioning "dual function" breaker, I should be good? My electrician is saying the "wires could still overheat" and wants to do a full rewire, but I don't necessarily buy that if the breaker is rated correctly for the wire gauge.
    – Saustin
    Commented Dec 18, 2021 at 19:37

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