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Our house was built in 1905 and while a lot of the electric has been replaced throughout the its 115 year life, a lot of the old BX cable (likely original or close to it) is still in use; mostly for lamps, lights, general use outlets (non-heavy duty).

The panel has been upgraded with modern breakers but I am still concerned about the longterm safety and risks of this old wiring.

I am wondering if there is anything (short of replacing all the wiring) to help alleviate concerns.

Specifically, would replacing all the breakers on this old wiring with arc fault breakers be something that would significantly (or totally) avoid any problems?

Or, am I overreacting?

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  • How hard would it be for you to run wires from the old boxes back to suitable grounding points? (i.e. your panel, your grounding electrode conductor system, or existing properly grounded circuits?) Jul 20 '20 at 3:02
  • @ThreePhaseEel anything can be done but it is especially challenging as the house is quite large (over 5,000 sq. ft.). I've traced all the runs and know which ones to use and which ones to not (for anything other than a lamp or a cell phone charger). But I will probably replace everything eventually. But in the meantime, I am wondering what can be done to alleviate a potential fire hazard. FWIW, the cloth/rubber jackets inside the electrical boxes does appear to be in good shape.
    – masedesign
    Jul 20 '20 at 3:11
  • Since the panel has been upgraded, has it been properly grounded? Are the gounds properly attached to the BX and the boxes? Are the fixtures properly grounded to the boxes? If so, you're probably miles ahead of most older homes that still have wiring from the early 20th century. Simply updating ungrounded outlets to grounded ones where possible would probably add more protection than most old houses have.
    – FreeMan
    Jul 20 '20 at 12:59
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I think you are over reacting With what you have provided original would be knob and tube it is still legal. BX is much safer If there is an issue it is inside the flexible conduit and that metal conduit is quite a bit of protection. Replacing breakers may or may not be possible with your existing panel and again your wiring is in conduit so I would not be concerned.

Depending when and Or the type of panel You have we may suggest getting it updated (especially if FPE™, StabLock™, Federal Pacific™ & Zinsco™ are the leading panels that have problems). Some obsolete panels do not have arc fault breakers available but are still good panels.

Note I have seen more problems with skinned NMB than with BX, MC or AC.

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  • "Depending when and Or the type of panel" something's not quite right there...
    – FreeMan
    Jul 20 '20 at 12:56
  • Most homes built in 05 have been reworked at least 1x if not more. I don’t see anything wrong with the possibility of the above as I have seen knob and tube that was updated in the 40’s with cloth (in wall K&T left in) and a new panel installed in the 60’s-70’s I was replacing that panel. In the late 90’s As the latest owner was updating everything to nmb and pulling the pushmatic panel. It may be possible that BX was used originally but I have not seen a Victorian with it as original. The overcurrent protection was originally fuses.
    – Ed Beal
    Jul 20 '20 at 13:46
  • I agree and understand, Ed, my house is 1890's and has gone through a couple of iterations, too. It was that particular sentence that seemed to have been auto-cowrecked or lost its train of thought that I was addressing in particular.
    – FreeMan
    Jul 20 '20 at 14:15
  • The panel is at least semi-modern (within the last 40 years) - all of the old BX circuits are junctioned above the panel and then 'converted' (so to speak) to NMB which enters the panel (that has traditional modern breakers).
    – masedesign
    Jul 20 '20 at 15:06
  • The biggie with an older panel is the limited number of spaces, and possibly a rule of 6 ) 6 double pole locations in the top of the panel , one of the 6 feeds the lower section. No single main. I recently removed a rule of 6 because of lack of breaker spaces. A new panel has more space or room to make splices (yours is fine. still code compliant with a gutter above the panel) the new panel being taller and wider I had to remove some blocking that was added to make the panel fit the owner liked that idea doubling their spaces in the panel. The main in the dining room so looks were important
    – Ed Beal
    Jul 20 '20 at 16:23
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Agree with Ed Beal's answer about your BX installation likely being safe. Especially so if you don't mess with it and start bending/cracking the brittle old insulation. But answering yr specific question, YES, using AFI breakers will significantly increase the fire safety of any electrical installation, so do it if it gives you peace of mind. Make sure you're attentive to which areas will require a combo GFI/AFI breakers under current code. Adding GFIs will also have the benefit of allowing you to replace 2prong outlets with (suitably labeled) 3 prong. GFIs will sometimes have difficulty holding on old wiring though due to minimal but nonzero leakage current.

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