I may be over thinking this. Getting ready to have new breaker panel installed in my basement. The walls are concrete block and do get damp (the old box rusted).
I'm thinking about mounting the new box on unistrut to space it off the wall.
Any problem with doing this?
Is there any reason I might have a preference for running the unistrut horizontal or vertical? Or for having it extend below or to the side of the box?
Unistrut is perfectly acceptable, and UL listed for support of electrical equipment. Loadenters stay with a building for a long time, so if it's that wet and damp, wood is not a good choice, unless marine grade. The panels are required to have the 1/4' bump out for airspace circulation behind, but as you saw sometimes that's not enough.
The objective is to keep the enclosure the same temperature as the room or warmer to prevent condensation. Attached to the wall it more closely follows the temperature of the foundation and becomes wet with condensation along with the foundation walls. Use galvanized strut instead of the powder-coated variety for better rust prevention on the strut.
I use zinc Nail on anchors for HD permanent fastening to masonry surfaces.
http://www.strongtie.com/products/anchorsystems/mechanical/nailon/
I like to run them horizontally (less material, as strong) and cut them to the same width as the panel, keeps the wall space clear for other equipment or studs.
One other thing to watch out for is if you have an overhead service and use a cable wiring method (SE or SER cable) Sometimes a leak into the gooseneck or service cap at the top of the service riser, or UV damage to the outer covering, will allow water to get inside the jacket. It will follow the wires down and drip straight through the meter enclosure, into the the cable feeding the loadcenter in the basement.
This will usually follow the wires to the main breaker or neutral/ground buss and cause serious corrosion there too. I always caulk the bottom cable leaving the meter to prevent this from happening. Bend the conductor apart sufficiently to get a good seal around the wire. Seen it happen many times and always requires another panel or breaker replacement.
MTW Ω
