What's the difference between AC and MC Cable

chefwongApril 25, 2010

Always have used BX in my house...which seems to = AC.

Aside from the looks of MC not having a paper sheath on the wires an a separate ground.

Out here in NYC BX land...the casing has always served as the ground for me.

Just curious as I saw a spool of MC the other day

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Ron Natalie

BX is not a defined term in the NEC. People tend to call any armored cable BX so it's by and large a meaningless term. AC will have a provision that will allow the sheath to be used as the equipment ground. MC may or may not, but it will also have a grounding conductor as well inside the sheath.

Either is fine as long as it is installed properly.

Did you have a question?

    Bookmark   April 26, 2010 at 6:11AM
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The biggest difference is that MC has full size ground wire while AC uses a combination of the jacket and a thin, aluminum bonding strip to function as the equipment ground. MC is available in a wider range of configurations with stuff like multiple and over-sized neutrals but for most residential purposes the two are interchangeable.

    Bookmark   April 26, 2010 at 6:37AM
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BX is an old manufacturer's name, not the name of the product.
Basic armored cable was developed in the early 1900s by Edwin Greenfield and Gus Johnson, who called their product BX cable. It has become a generic term for all armored cable like Kleenex is used for facial tissue and all refrigerators used to be called Frigidaires, regardless of the manufacturer.

    Bookmark   April 26, 2010 at 11:33AM
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The original armored was shown to cause sparks and could even become a heating element and cause fires.

The cure was the introduction of the small bonding strip to make sure the fault current would be adequate to trip an over-current device.

MC has a run ground, so the bonding strip is not needed.

    Bookmark   April 26, 2010 at 5:01PM
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Hi Chef,

Also a NYC resident and I always use AC or what most of us think of as "BX". What Mike says is all true and correct however there is just one more thing I would like to add...AC is definitely easier to work with as the jacket is steel and will flex and bend much easier especialy in runs where turns are involved. MC jackets are aluminum and do not provide the same "flex back" that AC does and can make it difficult to handle. Also just as a reminder, do not use Romex (plastic coated cable) as it does not pass inspection here. My next door neighbor had finished his basement and used it. Two years ago he sold the house and the home inspector discovered it and he had to rip open all the walls and change it out to BX.

    Bookmark   April 28, 2010 at 7:37AM
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Off topic but understood on Romex.
HOWEVER, you got me slightly curious but I do believe I checked when I did this

In my kitchen, I have both wiremould outlets and LV lighting underneath my cabs. I DID run BX to the wiremould strips.

From my Q tran transformer which sits inside a corner kitchen cab, I ran 4 runs of Romex inside the walls to that fed my Juno Trac 12 LV undercab lighting. ROMEX in this application is acceptable///up to code right ?

    Bookmark   April 28, 2010 at 10:20AM
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MC is available with steel armor.

    Bookmark   April 28, 2010 at 12:19PM
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