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My house was built in 1893. I was recently doing some electrical work in the attic, adding some light fixtures. While doing that, I noticed that several of the upstairs outlets were wired with old, worn-looking metal clad wiring. Since I wanted to replace the outlets anyway for style reasons, I replaced this old wiring with new 14/2 NM w/G (Romex) wiring. I also used the same romex for the new lights and switches (fished into interior wall cavities).

In further exploration, I've found this house has a lot of metal-clad wiring. Not only in places where you might want some extra protection, like a long run alongside the chimney or in a crawlspace, but also in places that seem totally straightforward and safe, like first-floor outlets and light switches. And it seems relatively recent (within the last 30 years).

Is there something I'm missing that might require metal-clad wiring in this house?

Bonus question: what's a good way to recycle lots of old metal clad cabling? :)

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Take the old wire to your local scrap yard, metal prices are currently high so you should get a nice bit of cash for it. –  Tester101 Feb 1 '11 at 17:17
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up vote 11 down vote accepted

The flexible armored wire you are seeing is often referred to as AC or BX cable. (BX was a brand name like Romex is for NM) Bx was used extensively prior to 1960ish and is still used today. There are no current code requirements that require this kind of cable in residential construction and it has almost all but been replaced with NM. As you have probably already figured out, BX uses different box connectors, and many of the device boxes you have in place were probably made to terminate BX cable.

Although it is perfectly legal to use, and actually quite safe, it is rarely used because of it's higher cost and relative difficulty to install and terminate. The only caution I would emphasize is the ground conductor in older BX. it was very common not to use a separate ground conductor when using BX, and often when there was a separate ground wire, it was a smaller AWG that the black/white/red current carrying conductors. this was never a problem if the BX armor was properly attached to the metal junction boxes and again properly connected at the panel, thus making a substantial grounding path.

As far as the bonus question. BX is heavy and probably brings a good price at the metal recycling brokers. A couple of years ago when junk metal was really hot, a good load would have been worth hundreds of dollars. It was a popular find for junk dealers and the target of theft.

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Since your house was built in 1893, i'm surprised you haven't found some old knob and tube wiring. Keep in mind, most houses didn't have electricity until after the 1900's. AC/BX was widespread by the 30's and 40's. –  shirlock homes Jan 30 '11 at 21:02
    
Great answer, shirlock! There are some remnants of knob & tube here, but no live k&t thankfully. I also discovered remnant pipes for gas lights, also disconnected, in the attic. –  Shimon Rura Jan 31 '11 at 1:40
    
As for why, it could be that the person who wired up the house had access to it - either "free", or at low cost. –  chris Jan 31 '11 at 19:24
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In Chicago they are still stinging from the cow fire, or the greenlee lobby has a lot of influence. Way above NEC standards. –  shirlock homes Jan 31 '11 at 23:55
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Any way to distinguish between armored cable, metal-clad cable, and flexible metallic conduit after it's been installed? –  Jeremy W. Sherman Nov 2 '12 at 21:16
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If the wire you have discovered was smooth and not knobby (wound) then it is likely what was called flex or "Greenfield" (after the man the designed it) cable, widely used in the 1920-1940 era. The metal casing was actually used for grounding.

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If you live in the Chicago area, "Romex" or nonmetallic cable has never been permitted. I'm not sure, but there might be other areas in the country that have the same requirement. As an electrician I wired my entire house in conduit and where I was fishing in existing walls, Flexible conduit(Greenfield).

For openers if you need to split up or add circuits at a later date you can fish additional wires through the condiut without having to open up walls. A second plus is the fact that rodents can't chew through metal condiut. Rodents DO in fact chew through wiring insulation that could either lead to circuit failure or fires.

Eric Long Amherst, Ohio

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