Does MC cable require an anti-short bushing?

The NEC requires it by name only for Type AC in 320.40. For Type MC, the connector or cable listing usually calls for it, and NEC 110.3(B) makes that listing instruction enforceable. When in doubt, install it.

How often does MC cable need to be supported?

Every 6 feet per NEC 330.30(B), and within 12 inches of every box, cabinet, or termination per 330.30(C).

Can I cut MC cable with a hacksaw?

Use a rotary armored cable cutter. A hacksaw leaves burrs and metal filings that damage conductor insulation, which violates NEC 110.12(B).

How do you connect an MC connector to MC cable?

Score and snap one convolution of armor, pull the waste off, trim the paper and mylar back, slide the connector on, and tighten the set screw or squeeze the snap-in body until the cable will not pull out by hand. Section 330.40 requires the fitting to be listed and identified for use with the cable, so the connector on the shelf must say Type MC on the carton.

Step by step

Set a rotary armored cable cutter about 8 to 10 inches back from the end and turn the crank until the wheel scores through one rib of the interlocked armor. Flex the cable at the score and the waste piece twists free. Do not use side cutters or a hacksaw. A hacksaw cut leaves a burr that will slice conductor insulation, which is a violation of 110.12(B) for damaged conductors and creates the exact ground fault the armor is supposed to prevent.

Peel back the kraft paper and the mylar wrap, and cut them flush at the armor. Leave them in the cable body, since the wrap protects the conductors along the run. Inspect the cut edge of the armor. If it is sharp, dress it with a file or a deburring tool.

Install the anti-short bushing, the red plastic insert, if the cable and connector listing calls for one. This is where crews get confused. Article 320.40 explicitly requires the insulating bushing for Type AC cable. Article 330 has no equivalent sentence for Type MC, so the NEC does not name it. The connector listing usually does, and 110.3(B) makes the listing instructions enforceable. Interlocked armor MC with a smooth-throat listed connector often does not require the bushing. When the carton is silent, put the bushing in. It costs nothing and no inspector has ever failed a job for having one.

Push the cable in until the armor is fully seated against the stop inside the connector, then tighten. On a set screw connector, snug the screw against the armor valley, not the crest. On a snap-in connector, listen for the click and pull test it. Section 300.15 still requires a box or listed fitting at every splice or termination point, and the connector must be secured to the box with its locknut so the metal path is continuous for 250.118 grounding purposes.

Support and bending

Section 330.30(B) requires Type MC to be secured at intervals not exceeding 1.8 m, or 6 feet. Section 330.30(C) requires it to be secured within 300 mm, or 12 inches, of every box, cabinet, fitting, or other cable termination. Section 330.24(B) sets the minimum bending radius for interlocked or corrugated sheath MC at seven times the external diameter for cables 19 mm, or 3/4 inch, or less. Kinking the armor to get into a tight ceiling is a failure waiting for the next inspection.

Field takeaway

Rotary cutter only, trim the wrap, bushing in unless the listing says otherwise, seat the armor fully, and strap within 12 inches of the box. Verify the connector carton says Type MC, because AC and MC connectors are not always interchangeable and 330.40 requires the fitting to be identified for the cable you are actually installing.