A little BS on BX cables Armored or Metal Clad Cables used in exterior installations.Wenatchee and Chelan Real Estate Inspection Services.

To understand any cable, including BX, the first step is knowing what a cable is in the first place, and where better to look for definitions than a dictionary? To get a handle on all of this, it’s important to know that modern BX cable is a term used interchangeably with AC (armor-clad) cable. Older BX cable is substantially different from the new stuff, and is no longer allowed by code, and this is the source of yet more confusion — but we’ll get to that later. The NM (Non-metallic) naming refers to the out sheathing that covers individual wires being non-metallic. It is different from conduit wiring or metallic sheathed cables, which involve individual conductors being protected and surrounded by a metal conduit or metal coil.

As soon as the cut is complete, grab the cable jacket below and above the cut and then twist it sharply. It breaks the armor without the saw getting in touch with inside wires. It’s therefore essential to only buy bx wiring and use BX cables if either the task or the electrical codes require you to do so. If your old BX cable is in good condition and can still manage to carry higher power demands, you’ve no reason to replace it.

Pros and Cons of Romex Wiring

As you can see they do not have a protective PVC outer jacket that would allow the use on exterior applications. Where MC Cable may be used in exterior applications but must be suitable for exterior or direct burial. This type of MC Cable will have a continuous PVC outer jacket. There were originally two initial versions of armored cable. One was called “AX” and the other “BX,” with the “X” standing for “experimental.” The “BX” version became the one that eventually was produced, and hence the name “BX” became the common name. “BX cable” is the sort of term most homeowners will only hear about in passing.

@Armand I’d be surprised if there is a single instance of any connector securing any MC to any plastic box in the house. With the receptacle box I was working on today that prompted this question, the MC seems to just be floating in there, I can freely pull slack in any out of the box. Romex wires are also cheaper compared to metal-sheathed wiring such as BX wires.

BX WIRE 8-3 PLUS GROUND (price as per METER) (Final Sale)

The electrical codes require conduit installations in such instances. Another distinction is that some types of BX cable can be installed in exposed locations, either indoors or outdoors. NM cable and wiring must always be installed in an enclosed location . Always be sure to check with your local building and electrical codes as to whether BX cable may be left exposed. The biggest difference between the two cable systems is that MC has full size ground wire while AC uses a combination of the jacket and a thin bonding strip or wire to function as the equipment ground. The bonding wire is unique to AC cable and this allows the outer metal armor in conjunction with the bonding wire to be used as an equipment ground.

Because of the difficulty in making a fair apples-to-apples comparison, homeowners understandably struggle with unpuzzling cost comparisons when electrical cable is involved. At Home Depot, 250 feet of Southwire 12/2 solid copper, aluminum-armored BX cable costs $198, while the same MC cable costs $199. Wholesale prices aren’t readily available for Southwire BX and MC, but the Atkore pricing difference is less than $8 for MC versus BX cable.

What is Romex Wire & NM Cable?

Three prong outlets cannot be installed on BX wiring, unless a GFCI outlet is used. Since it is ungrounded, new wiring cannot be extended off of BX wiring. For example, if you want to add a new outlet in a room and there is a nearby BX outlet, this outlet cannot be used to power the new outlet. In addition, while home improvement stores still do carry BX cable, do-it-yourselfers will find a far greater selection of NM cables at retail outlets. But occasionally you might open up a wall or ceiling and encounter a type of ribbed metal-clad cable called BX.

In a number of cases, I have old AC/BX cable going in to plastic junction, receptacle, or switch boxes. There is also a copper grounding wire that is left bare and uncoated. There is also paper added within the cable to separate the conductors. This lock nut and connector had to be tight, otherwise the circuit would lose it’s ground path. Let’s say the circuit goes in and out of 10 different boxes before the circuit finishes.