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What is BX or Armored Cable?


BX or Type AC Wire

Older BX Wire on Top, New Type AC Wire on Bottom

Copyright 1986 McGraw-Hill, Inc
When performing electrical renovations on your home, you have the choice of using either NM wiring (non-metallic sheathing, also known as Romex) or with BX wiring (also known as metallic sheathed cable, type AC, or armored cable).

What is BX Wiring or Type AC?

Bundles of insulated wires sheathed in a very sturdy metallic "armor."

When was BX Wiring or Type AC Developed?

BX or Type AC is one of the earliest types of electrical cable developed for both residental and commercial uses in the early part of the 20th century. Early forms of BX can still be found by homeowners renovating their homes. "BX" is the older term for this type of cable. It's not certain how this term came about, but it may have something to do with the cable first being produced in the Bronx, New York.

Because it's Old, is BX Wiring or Type AC Wiring Bad?

No. It is very good wiring. Romex or NM wiring is not necessarily "better" because it is newer.

Are There Instances in Which the Physical Condition of BX Wiring or Type AC Wiring is Bad?

Yes. If the armor is nicked, cut, or shredded. Also, if the wires within display degrading of their rubber insulation. If old BX wiring is in good condition, though, and can carry today's higher power demands, there is usually no reason to replace it.

Should I Use BX Wiring or Type AC Wiring Over Romex?

There are no inherent plusses or minuses associated with armored cable. As a do-it-yourself electrician, you may find it easier to handle and cut Romex, though.

How Do You Cut BX or Type AC Wiring?

Very carefully. You can cut it with a hacksaw, assisted with a very strong pair of wire snippers or pliers. With this method, though, it's very easy to nick the insulation on the inner wires--not to mention lacerating your fingers on the sharp metal armoring. If you think you will be doing a lot of cutting, invest in cutter, such as the Roto-Split.

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