Mounting electrical box to lally column?

There are metal epoxies that would mount a plate to the column.

Hilti powder actuated nail gun and Hilti threaded studs (1/2" long, for steel). Shoot in two studs to line up with the holes in the back of the electrical box, then secure with nuts and lockwashers. In the event the box needs to be removed, you can readily grind off the studs with an angle grinder and touch up paint it.

All sorts of masonry anchors out there, I've used tons to mount various electrical boxes to concrete and block walls. I used to work in one of the first poured concrete buildings, made about 1917, the support columns were round and all electrical boxes were mounted that way with conduit running up to the ceiling to junction boxes. The column diameters were about 4' on the the floor we had the warehouse on, would have taken a hell of a hose clamp to span that.

Stan

Weld a piece of 1/8 x 1 across the column & screw to it. Bob

The problem is that these columns (I call them lally columns in Northeast USA) are steel tubes around 4 inches in diameter, filled with concrete. Will a hammer drill with a masonary bit drill though steel? I will have to experiment.

Thanks, Andy

Piece of 1" plywood U-bolted to the column.

On Mon, 17 Aug 2009 11:15:54 -0700, the infamous "Calif Bill" scrawled the following:

I don't know if it's to code, so check with an electricaltician (Bruce Bergman, a Sparky here on RCM), but drilling the column with a masonry bit is simple, and various methods of fastening through it are to code. The simplest is a plastic insert in an oversized hole for that particular screw. It's an additional 5 minutes over the 5 minutes with the Hilti, but not if you have the masonry bit and don't have a Hiltiwhammer.

-- If you are distressed by anything external, the pain is not due to the thing itself, but to your estimate of it; and this you have the power to revoke at any moment. -- Marcus Aurelius Antoninus

rangerssuck fired this volley in news: snipped-for-privacy@26g2000yqk.googlegroups.com:

The common way here is to power-nail a mounting plate to the column.

LLoyd

I kind of like the hose clamp. Might look better if the hose clamp was silver brazed to the box and the box painted to match the column.

The obvious solution that would likely be used by an electrician is cable ties. Quick, Easy, and Cheap. Would look better if some clips were screwed to the box, instead of running them thru the box.

Dan

Dan

=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 Dan

=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 Dan

Thanks for all the replies. So far, the ramset (Hilti) solution is out in front. I will post to the dropbox with my solution.

Best Regards, Andy

Years ago I had to tap many 1/4 20 holes in steel angle that had concrete poured directly behind it. My solution was to have a bunch of #7 drills to get through the steel and then I cleared out a space in the concrete with a punch so the tap would not get destroyed. The drills were good for about one hole before needing to go back to the sharpener.

You could start with a metal drill to get your hole location and not go through to the concrete. Then use a sharp carbide drill for concrete to finish going through the steel and into the concrete. Don't use a hammer drill while drilling in steel, just rotary. Then use concrete anchors to hold your box.

Hey Andy,

Metalworking group or not, the easiest thing to do is "box in" the Lally column, with 2 X ?? or even "thinner". "Pin it" through the top adjust hole of the Lally to keep it in place.

Brian Laws>Hi Folks. I am in the process of wiring a basement workshop. I hope

I would not use a Ramset powder actuated tool on filled structural steel lally columns like that, part of their strength is the concrete inside, and if you fracture it the strength is reduced.

Myself, I'd stay with the hose clamps to attach a chunk of Unistrut vertically on the pole, or tack-weld a piece of Unistrut to the column for the conduit risers and some flat plate to mount the boxes - that won't affect the concrete filling, and small tack beads shouldn't hurt the steel column strength enough to matter.

If you attach the Unistrut to a floor bracket and anchor the top off to the beam, you only need one hose clamp in the middle around the column or a few short tack welds, mainly to keep it from bending when you trip over an extension cord.

If these were open internally reinforced concrete columns (Sonotube cardboard forms) I'd still be wary of using a Ramset on them, for the same reason - fracture the concrete and you are counting on the rebar alone to carry the entire load.

(This is why they are reinforcing freeway bridge columns with steel bents on the outside - if the concrete fractures in an earthquake, the steel outer skin will hold all the pieces in place and keep it from failing.)

You can put a 1/4" hole with a carbide impact drill fairly safely and use a plastic anchor or a zinc sleeve and pin fastener, but a Ramset can cause a lot of damage with a single shot.

(Not to mention the fun of a "Come-backer" nail bouncing off ultra hard old concrete and moving at ballistic speeds. Been there, Done that, sweating my butt off in a heavy jacket for padding...)

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Not an issue. The concrete provides only compressive strength and that is not compromised even if it has some cracks in it. The 1/2" long pins won't fracture the concrete either.

If you're going to weld, just plug weld the box to the column via the normal box mounting holes and be done with it. It will be a much cleaner looking job, and again can be ground off with an angle grinder if the box needs to be removed. I've plug welded several electrical boxes to frames made of square steel tube and it works fine.

Good grief, $20 in materials to do the job of $0.50 worth of Hilti pins and loads, or $0.10 of weld?

You need to understand that concrete provides compressive strength only, it could be dry stacked concrete blocks and provide the same strength. The rebar is always what provides strength against flexing loads.

Which is exactly why fractures in the concrete inside a lally column are irrelevant and why shooting the boxes on with Hilti pins is fine.

A Ramset or Hilti can cause a lot of damage if used on the web sections of a non-filled block wall, they will do no harm at all to a concrete filled steel column.

Also not an issue when shooting the proper 1/2" pins into the steel column.

Besides, the Hilti is kind of like a firearm, and the second amendment ramifications of this job are huge. Sorry, I just couldn't resist.

Seriously, my initial thought was similar to Bruce's - that you could really screw up the concrete and compromize the strength of the column. But Pete's explanation sounds pretty good. The concrete is only providing compressive strength, a fracture is not removing any material (assuming that there arent any huge voids), so this should work fine, and take all of couple of minutes, start to finish. And, it will smell like gunpowder, which is always good for the folks in this group.

You can't attach the box with cable ties. We used saddle strap which is a cut to fit type of hose clamp. If you can find large enough hose clamps most inspectors would probably be OK - use two so the box can't twist. If the box is below six feet feet from the ground you may need to protect the cables with plastic conduit to that height.

One can mig weld an electrical box up in less than 15 seconds. Works great, less filling.

Gunner

Whenever a Liberal utters the term "Common Sense approach"....grab your wallet, your ass, and your guns because the sombitch is about to do something damned nasty to all three of them.

On Fri, 21 Aug 2009 04:06:55 -0700, the infamous Gunner Asch scrawled the following:

What filler rod do you use to fasten them to concrete columns, sir? (This I -gotta- hear. ;)

Doesn't the galvanizing f*ck up the weld? I think I'd drill the mounting hole just a touch bigger (to drill off the galvy) & plug weld.

Bob