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PittsburghClint 07-03-2011 01:59 PM

Installing an electrical recepticle on a basement structural support post
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I am going to install a new 20 amp circuit in my unfinished basement to supply some much needed outlets to one side of the room. I'd also like to have recepticles in the center of the basement, but don't want to install up in the ceiling. Given that there is no wall in the center, and there is a steel structural support, I'd like to install the outlets on to it, but am unsure if that's a gross violation of best wiring practices.

The house itself was built in 1930, and I know (or think) that the way the wires are run at weird angles across and around the ceiling joists in the basement, rather than parallel or perpendicular with guards, is not correct, but that's pretty standard with older homes around here. I don't ever see this basement having a finished ceiling - to cover the hot water pipes (for the radiators) would make the ceiling ridiculously low.

I don't want to build a floor to ceiling encasement of the pole, although if that's the best way to do this I guess I would. I'd prefer to just run some armored cable down about halfway to a supported box (maybe built from wood and steel and attached to the pole with large hose clamps). If I did that, would it be a bad idea to use some conduit to give the metal clad cable running down the pole some added protection and to affix that to the pole as well?

Any insight would be appreciated - thanks!

kbsparky 07-03-2011 03:16 PM

A metal outlet box welded or bolted to the column would be fine. You could feed it with either a metal conduit, or piece of MC cable.

PittsburghClint 07-03-2011 07:07 PM

Great, thanks for the tip KB!

WillK 07-03-2011 10:38 PM


Originally Posted by kbsparky (Post 679130)
A metal outlet box welded or bolted to the column would be fine. You could feed it with either a metal conduit, or piece of MC cable.

I might be overcautious on this, and often in residential structure things are overdesigned, but I generally am inclined to point out that either welding or drilling or cutting a steel support column creates stress concentrations that will reduce the strength of the column.

A method that would not alter the structural integrity of the column would be to treat it as if the column was a pipe being mounted to a wall with a conduit clamp or something similar, and use that to mount a board to the steel column and that board could be used for mounting the junction box. The wire could be brought in with conduit. Or secure a board to the column with a u-bolt.

PittsburghClint 12-18-2011 04:30 PM

This post is old and the project is long done but wanted to follow up. I used two 9" adjustable hose clamps and attached the box directly to the post via running the clamps through rear knock out holes of the junction box. I then wrapped black rubberized foam around the sides of the box and the pole to give some protection/sealant and give it a better appearance. Looks good and no hazards as far as I can tell.

joed 12-18-2011 05:41 PM

Hose clamps through the box knockouts is in no code compliant. Hose clamps to hold a piece of wood then fasten the box to the wood would have been a better choice.

PittsburghClint 12-18-2011 06:39 PM

Good point. Easy enough to fix. Thanks for the insight!

Missouri Bound 12-18-2011 07:17 PM

A beam clamp is a U-shaped device which has the sole purposeof mounting electrical fittings to a steel beam. A good hardware store, big box store or an electrical supply house will have what you need. It's commonly tapped with 1/4-20 holes to fasten the fitting or in your case the box directly to the clamp.

Red Squirrel 12-18-2011 07:58 PM

What I would have done is built a square "box" around the post out of wood and mounted the box that way. Though this would increase the size of the post, which may not be desirable depending on the situation.

Looking at the way that post is mounted I'm even wondering if it serves any purpose from a structural standpoint. I would expect the perpendicular "beam" to be much bigger. Don't take my word for it though, I'm no expert.

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