Armored Cable (Type AC)

Old-timers call it BX. The armor plus its internal bonding strip forms the equipment ground, which is why the anti-short bushing — the red 'redhead' — matters so much at every cut.

In a remodel I like AC where I can fish it, because it brings its own protection into old plaster walls without me pulling a separate ground.

When it applies

Type AC cable gives you flexible metal armor around the conductors, so you get mechanical protection without pulling a raceway. It suits dry indoor spots, run exposed on structure or fished through finished walls where the armor guards the wire.

Common mistakes

• Skipping the anti-short bushing, the little red one, at the armor cut. That plastic sleeve keeps the sharp edge from nicking the insulation.
• Using AC cable in wet or damp locations where it does not belong.
• Bending it too tight and crushing the armor spiral.

In the field

Every apprentice I train learns the red bushing rule the hard way once. I had one leave it out on a whole apartment and the inspector caught a single missing bushing in a junction box. We pulled covers on every box to prove the rest were in. Now they never forget: cut the armor, slide the bushing, then terminate.