Can MC cable be tied to ceiling grid support wires?

No. NEC 300.11(B) prohibits supporting cables from the ceiling grid or its support wires. Install independent support wires, secured at both ends and distinguishable from the ceiling wires, and clip the MC to those.

How often does MC cable need support above a drop ceiling?

Every 6 feet and within 12 inches of every termination, per NEC 330.30. Fished runs in concealed accessible spaces are exempt where securing is impracticable, but new open runs are not considered fished.

Can I Support MC Cable With Ceiling Grid Tie Wire, or Do I Shoot My Own?

A user asked the app whether MC cable can hang from the ceiling grid support wires or whether they need to shoot their own. Shoot your own. NEC 2023 300.11(B) prohibits using the ceiling support wires or the grid assembly of a fire rated or nonfire rated suspended ceiling as the support for raceways, cables, or boxes. The grid wires hold the ceiling; your wiring gets its own independent support wires, secured at both ends, and those added wires must be distinguishable from the ceiling wires by color, tagging, or other effective means.

What an inspector wants to see

The clean setup is dedicated support wires shot to the deck, marked with paint, colored jacket, or tags, with MC cable tied to them using listed clips or tie wraps suitable for the purpose. Battery clips that snap on independent wires, or caddy style MC clips on the wires, both work. Tying MC to the same wire that carries a grid main runner is the classic red tag, even if the wire looks beefy enough, because a fire rated ceiling assembly depends on those wires doing only their listed job.

Spacing still follows Article 330

Independent support does not change the intervals. 330.30 requires MC cable secured at intervals not exceeding 6 feet and within 12 inches of every box, cabinet, fitting, or other termination. Fished cable in accessible ceilings gets the 330.30(D)(2) allowance where support is impracticable, but a new open plenum run laid in by hand is not fished, so plan supports every 6 feet. Cables smaller than 10 AWG have additional securing language, and bundles need a look at derating once more than about 20 current carrying conductors ride together.

Above the tiles is not a shelf

300.11 also means MC cannot lie on the tiles or rest on the grid tees, and 300.22(C) governs what wiring methods live in that plenum space at all. Standard MC is fine in most plenums; the support method is what fails jobs. A few boxes of pre cut colored support wire and a powder actuated tool save the whole punch list.

Every job has one odd code question. Ask BONBON answers it with the NEC section cited, right from your pocket.