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While widely used in the past, BX cable is hardly relegated to the past.
With most electrical projects, it’s possible for you to use either metal-armored BX cable or plastic-sheathedNM cable.
BX Cable
BX is a name for metal-armored electrical cable for indoor or outdoor use.
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BX’s metal sheathing looks like a single, ribbed metal tube.
However, the sheathing is a metal strand that runs in a helix-like or twisted manneraround the wires.
BX is contrasted with a newer cable, NM, which stands for “non-metallic.”
Romex is one popular brand of NM electrical cable.
Where to Use BX Cable
BX cable can achieve grounding through the outer metal casing.
This casing needs to be attached to metal boxes.
Check with your local building and electrical codes to see if BX cable may be left exposed.
Wires within the armor may display degradation of their rubber insulation.
But this may just be at the exposed ends.
If you rip back the metal sheathing, you may find that the insulation is still good.
Unless the job specifies BX cable, use NM plastic-sheathed wiring.
NM wire is lightweight, easy to handle, and inexpensive.
It’s simple to cut, rip, and strip, plus it pulls effortlessly through holes in studs.
BX cable’s metal sheathing can be hard to cut without nicking or severing the inner wire.
NM cable presents the danger of nicking inner wires.
So, NM cable always needs to be protected.
Running NM cable through holes drilled in the center of wall studs is one way to protect the cable.
Home improvement stores usually carry BX cable, though you’ll find more choices of NM or Romex cable.
The tool is calibrated to cut the metal but stops short of touching the inner wires.
Early forms of BX can still be found by homeowners renovating their homes.
It is not certain how the term “BX” came to represent metal-armored cable.
Early accounts of BX cable being used date back to 1910.
Shapiro, David E.Old Electrical Wiring.
2nd ed., Mcgraw-Hill, 2010.
