running conduit from basement to attic


Old 08-24-11, 07:14 PM
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running conduit from basement to attic

Howdy folks!
My house is a classic rancher from '67, unfinished (for now) basement.
I need to install a ceiling fan 9run new circuit), and I know in the near future I also run at least 2 20A & 1 220v to the garage, only route there is up through attic then drop back down.

Of course the panel is in the basement.
So i'm thinking about going ahead and running a big conduit (or 2) from the basement to the attic, to serve not only my needs now but with enough space to run circuits later.
I figure I'll find a spot that is inside a wall & between joists, drill a hole from the basement, then go in the attic and drill a corresponding hole (and pray they match up)
so here are my questions..
1 - w/ only 7'9" height in the basement, is it feasible to get say a 8'6"(?) long conduit (assuming PVC) up there? Does it flex enough for that?
2 - any magic tricks to getting the conduit to "find" the hole up top? maybe drop a guide wire from above?
3 - I know there are NEC fill limits. However - what are the practical limits for being able to push wire up later into an already-occupied conduit? I see this as a "those who have done it" thing... i'm thinking about teh headache 5 years from now ;-). should i just go all out for say 1.5" conduit? maybe do 2 while at it?
4 - How do you hold the conduit in place once it's in there? rely on a junction box at the base for that?

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Old 08-25-11, 06:31 AM
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I would be just as easy to fish cables into place instead of the conduit sleeve.

A string with a small piece of chain as a weight works well to get the string between floors. You can also drill two holes at the bottom. You can look in one while you fish the wire into the other hole.
Old 08-25-11, 08:31 AM
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An open conduit used as a duct to run cable between floors needs to be firestopped to preclude it being a means for fire to pass between the floors. That kind of defeats the purpose of using the duct in the first place. Further, if this was an outside wall then you have thermal insulation to contend with and running the duct (conduit) would be all but impossible.
Old 08-25-11, 05:29 PM
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If you really want to run conduits to your attic, I'd run several smaller conduits such as maybe 2 or 3 - 3/4" conduits through an interior wall (I prefer EMT with steel setscrew or compression fittings). 90 each conduit with an LB and run them at least 8 to 10 feet further, but horizontally and preferably to a gable wall where you can mount a junction box at a comfortable working height. I'd use a junction box such as a 4" square deep box with blank cover on each conduit, top and bottom, and use a riser clamp to keep the conduits from sliding back into the basement. Fireseal all openings. One day when you do decide to pull a few new circuits, the LBs and the horizontal runs in the attic will keep the wires from falling out of the conduits on to the basement floor.
Old 12-04-11, 08:28 AM
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Well I ended up doing it. The hardest part really was finding the right spot that I could ID from both under the floor and in the attic, and know the holes would line up - and not have a chance of an AC wire running across the joists to worry about hitting.
Found an interior closet wall where I could tell exactly where it was from below b/c of a phone wire.
Drilled 2 1.5" holes, above and below. Pushed 9' of PVC conduit up from below, the longest I could b/c of the floor getting in the e way (even that only b/c I could bend it). ran 2 pipes, first was easy b/c the 2nd hole provided viewing. 2nd took more work and a buddy ;-)
Clamped in place on both ends, caulked in firestop insulation spray and put a junction at the top. Ran the few lines I needed for now, then packed in insulation from bottom and top. Should be good to go now.
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