I defy anyone to bring power to a metal building, and fail to have it bonded. Your usuall construction methods pretty much guarantee that there is not only a bond, but a very good one.
That said, Greg refers to an oddball situation that I, with my primarily commercial background, just never would have imagined.
I can't imagine anything but steel boxes used with 'light steel framing' studs, but it seems someone did. Where that person got the idea that nail-mounted plastic boxes and romex were suitable for use with that construction method is beyond my understanding. The end result was that a fault made the entire frame 'live,' just waiting for comone to act the role of the ground wire.
Barns can be another thing completely, and that is where you can see the difference between 'legal' and 'good design.'
I would tend to treat everything above head level as a 'dry' location, but I would also give some serious thought to corrosion issues. Both animal waste and fertilizer can create some pretty severely corrosive locations.
MC has two strikes against it: the connectors are 'dry location' only, and most has an aluminum jacket. Aluminum readily corrodes when exposed to alkalies, such as fertilizer.
Romex actually might be a better choice ... assuming that critters can't chew it, and you can call the location 'dry.'
If you have to mount anything to sheet metal (as opposed to the structural pieces), only toggles will work.
Last edited by renosteinke; 07/19/12 04:39 PM.
