Requirements for protection of MC cable?

[toller]

I have put off installing a new circuit because I dread the thought of drilling through 40 floor joists.

I saw some MC cable in HD that is only slightly more expensive than romex. My recollection is that MC can be fastened to the bottom of floor joists as long as they are at least 7' from the floor below.

Is that correct, or am I misunderstanding something?

I have never used the stuff before. Since I am only using one length, I suppose I can handle the 2 cuts with a hacksaw. Is there anything else to be concerned about? Thanks.

[Chris Lewis]

According to toller :

It's effectively considered conduit.

Be extremely paranoid about nicking the conductor insulation. Theoretically, you're supposed to use a special tool for it. But with care, a hacksaw will work and not take long. You don't have to cut all the way around. Just cut one turn of the wrap. Sometimes a pair of angle cutting pliers carefully wielded will shorten the struggle.

Once you've cut it, you need to put a bushing on the conductors to protect them from the edge of the armor.

The sheath has to be carefully clamped at both ends. Don't cinch it down so far that you crush the bushings and puncture the insulation.

IIRC, MC has a real ground conductor (equivalent to the only type of BX available here). Terminate it properly just as if it was romex.

Frankly, I still prefer drilling the joists and using Romex. With a 7/8" auger bit (and especially if you can beg, rent, or borrow a 1/2" angle drill to get the holes straight) it goes pretty fast.

[DanG]

Bend the MC cable back on itself, full 180. The metal sheath will pop open, cut with diagonal cutters or hacksaw, reshape the MC, done deal.

I, too, would drill the joists. Speedbore, good drill, 30 seconds per hole. Romex or MC through the holes.

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