Metal-Clad Cable (Type MC)

The key difference from AC is that MC has an actual green-or-bare grounding conductor inside, so it does not rely on the armor as the ground path. That makes it the workhorse for commercial fit-outs.

Watch the listing, though — standard MC is not for wet locations or direct burial unless it is the specific type rated for it. Grab the wrong roll and you have a corrosion problem in a year.

When it applies

Type MC is your workhorse when you want a jacketed cable with a real, dedicated equipment grounding conductor inside. Unlike old AC cable that relied on the armor and bond strip, standard MC carries a green wire, so the interlocked armor is mechanical protection, not the ground path. That earns it a much wider list of permitted locations.

Common mistakes

• Treating the aluminum interlock armor as the equipment ground, it is not, land the internal EGC.
• Skipping anti-short bushings, the red heads, at the fittings where the cut armor edge can nick insulation.
• Using standard MC in a wet location when only the listed wet-rated or hospital versions belong there.

In the field

I keep a bag of anti-shorts taped to my strippers. Every armor cut gets one before the connector goes on. It is a two-second habit that has kept my grounds clean through more than one megger test.