Wrapping Beams

[petersonra]

MC?

 

[Cow]

How wide are the beams?

It may be simpler to come into the back of a wide pull box than use multiple LB's and nipples..

 

[AKElectrician]

Without dimensions hard to help, but I’d shoot for this.

 

[PaulMmn]

Is that isometric diagram a real diagram of the actual installation? If so, that massive girder is holding up smaller girders that would provide a straight-thru path for conduit.

 

[hillbilly1]

Prices seem to vary widely, but what about using pulling ells? Would definetly be easier to pull wire through with that many turns.

 

[Eddie702]

How was it estimated and how was it shown on the drawings? If you didn't know before the bid it could be a bid adder

 

[Alwayslearningelec]

If you use 30° offsets each beam would be 120° of bend, 360/120=3 so after every third beam you would need a pull point. Use 45° offsets and you would need a pull point after every second beam. Multiple pull points like using many LB's make wire pulling more expensive.

So in a siutation like the attached. Just talking about one of pipes which id 3/4" emt with 8#10'w. What or at what points would the setup/breakdown of equipment be for a wire pull with so many LB's?

 

[Alwayslearningelec]

Yes but they increase labor over using offsets. Even pull boxes are easier that LBs be cause you can pull straight through

I don't quite follow. So instead of the LB's a box would be better and at the same locations?

 

[Alwayslearningelec]

What is distance between the conduit runs and how wide is the flange on the bottom of the beam ?

Conduit run is about 400'. Not sure about bottom of beam flange width.

 

[Alwayslearningelec]

Yes as MK stated and that was my point. A million LB's will make pulling wire much more expensive. With a straight-thru pull box every 360° you might even be able to pull through a few saving even more in labor cost.

As I stated above I understand what your saying but not the layout of the boxes in lieu of the LB's. Still need to get around the beam.

 

[Alwayslearningelec]

I was thinking the exact same thing. I have used used small 4x4" wireways before, not sure how short they come off hand.

I dont really like the LB idea. Although it may look the best, LB's are both expensive and generally a pia.

Ive done a lot of work in old mills with big timbers and we did offsets to get under all the beams, but this was mostly lighting and fire alarm so it seemed like we had boxes so frequently for devices that we never needed pull boxes.

Willie and felon, thank you very much. I can't picture what mean. So conduit would be run tight to slab then drop down( by the beam) and connect directly into a wireway under the beam, then exit the other end of the wireway with conduit back up to the slab?

 

[Alwayslearningelec]

Prices seem to vary widely, but what about using pulling ells? Would definetly be easier to pull wire through with that many turns.

Isnt pulling ell same as the LB?

 

[Alwayslearningelec]

The raceway was what I was thinking about when I inquired about dimensions. If the conduits are close to each other I think it would definitely be worth considering.

What is that?

 

[winnie]

Willie and felon, thank you very much. I can't picture what mean. So conduit would be run tight to slab then drop down( by the beam) and connect directly into a wireway under the beam, then exit the other end of the wireway with conduit back up to the slab?

That is what I was thinking as a possibility. If you want the conduit to drop down flush with the beam, you can't have a bend to transition to the bottom of the beam. So you could have 2 LBs at the base of the beam (for the conduit coming down and going up on the other side). Between the two you would need a short bit of conduit.

The problem is that you can't pull _through_ an LB, so the above approach requires 2 pulling operations per beam.

If you replace the pair of LBs with a wireway that goes across the bottom of the beam, then you can pull wire from beam 1 to beam 2, feed the wire into the 'up' conduit and pull to beam 3, and then snap the lid on to the wireway. 1 pull.

-Jon

 

[hillbilly1]

Isnt pulling ell same as the LB?

Not quite, they are much shorter.

 

[LarryFine]

To me, wrapping every beam for 400' is ridiculous. I repeat my previous suggestion to look for the nearest vertical surface or row of columns. Those beams can't be so long that an alternative to wrapping is out of the question.

 

[oldsparky52]

To me, wrapping every beam for 400' is ridiculous. I repeat my previous suggestion to look for the nearest vertical surface or row of columns. Those beams can't be so long that an alternative to wrapping is out of the question.

I would definitely be asking for more money to "wrap" the beams.

 

[AKElectrician]

Without dimensions hard to help, but I’d shoot for this.

Can you back to back 90 the beam?

Use a C condulet like I drew and then you would be 2 bends around the beam one bend at the ceiling dropping your last bend into a C. Repeat.
Lube the heck out of it and pull through 720 degree of pipe.

 

[AKElectrician]

Can you back to back 90 the beam?

Use a C condulet like I drew and then you would be 2 bends around the beam one bend at the ceiling dropping your last bend into a C. Repeat.
Lube the heck out of it and pull through 720 degree of pipe.

And if your scared of that put a c up high in the straight shot also.

 

[ActionDave]

To me, wrapping every beam for 400' is ridiculous. I repeat my previous suggestion to look for the nearest vertical surface or row of columns. Those beams can't be so long that an alternative to wrapping is out of the question.

I agree.