Exposed BX cable

[John Gromkoski]

What is your opinion or the requirement regarding Armored Cable (BX) exposed outside of a wall at the interior of a home? Is it required that it be "in wall" or in an approved conduit? Can it be exposed? I see it often and always call it out as being improper. Just wanted other thoughts.

[Robert Meier]

It is permitted by the NEC to be run exposed unless subject to physical damage, which is a completely subjective requirement. IMO unless there's a chance of being easily damaged then it's fine if run exposed. The NEC specifically permits AC cable to be run on the underside of floor joists if stapled to every joist.

320.10 Uses Permitted.
Type AC cable shall be permitted as follows:
(1) For feeders and branch circuits in both exposed and concealed work
(2) In cable trays
(3) In dry locations
(4) Embedded in plaster finish on brick or other masonry, except in damp or wet locations
(5) To be run or fished in the air voids of masonry block or tile walls where such walls are not exposed or subject to excessive moisture or dampness
FPN: The “Uses Permitted” is not an all-inclusive list.
320.12 Uses Not Permitted.
Type AC cable shall not be used as follows:
(1) Where subject to physical damage
(2) In damp or wet locations
(3) In air voids of masonry block or tile walls where such walls are exposed or subject to excessive moisture or dampness
(4) Where exposed to corrosive fumes or vapors
(5) Embedded in plaster finish on brick or other masonry in damp or wet locations

320.15 Exposed Work.
Exposed runs of cable, except as provided in 300.11(A), shall closely follow the surface of the building finish or of running boards. Exposed runs shall also be permitted to be installed on the underside of joists where supported at each joist and located so as not to be subject to physical damage.

[Jim Thompson]

what about inside a basement in a residential home? would this be considered a damp or wet location? I want to run AC cable from an existing junction box fed by conduit on the ceiling to tun another service/fixture. can i use exposed ac cable?
if this is permitted, can i clamp the ac cable outside the ceiling / finished drywall?

[Jim Port]

I doubt the basement would meet the NEC definition of Location, wet. If it does you have other issues like serious waterproofing deficiencies.

If the basement were conditioned I don't think it would be a damp location either. This is a case by case basis. The NEC says "moderate degrees of moisture". What that is depends on the person judging the install.