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-   -   What conduit should I use? (http://www.diychatroom.com/f18/what-conduit-should-i-use-110429/)

mulltron 07-11-2011 07:28 PM

What conduit should I use?
 
Hey All,
I bought a house that has a shed with a 120/240 subpanel. One of the 120 leg wires is out. When we tried to pull the old wire out of the conduit it isn't budging. It looks like the previous owner put in a few nasty 90 degree bends and the wire nearly filled the conduit anyway.

There is a huge concrete driveway between the main box and shed and there isn't a good path to get to dirt and bury a conduit.

I am running running 3 #8 (120, 120, N) and 1 #10 (GR) THWN from a 40A breaker on the main box. Ground rod at shed is taken care of.

I am going to have to resort to above ground conduit.

What size of conduit should I use? The old conduit was 3/4" and I have been told 5 #8 THWN can fit, but now that I can't use the old conduit, is 3/4" the right size or would 1" be better to go with to make it easy to pull the wires through? What should the conduit be made out of? Is there anything you would put around the conduit to make it any stronger? If I am running it over sidewalk what is the appropriate way to do it? Any other pointers to give me so that I don't have to replace conduit for quite some time?

Thanks in advance for the advice!

mpoulton 07-11-2011 07:53 PM

For an exposed installation that could be subject to vehicle traffic (accidentally), I'd say rigid pipe (RMC) is the only suitable solution. I'm sure the electrical subcontractors on here will chime in, too. My solution would be RMC across the above-grade portion, anchored to the concrete with two-hole straps at close intervals. I'd use an LB at each end, with a rigid sweep 90 going underground. Transition to PVC below grade after the rigid sweep. I'd use 1"; it's much easier to pull through.

mulltron 07-11-2011 08:07 PM

Quote:

Originally Posted by mpoulton (Post 684309)
For an exposed installation that could be subject to vehicle traffic (accidentally), I'd say rigid pipe (RMC) is the only suitable solution. I'm sure the electrical subcontractors on here will chime in, too. My solution would be RMC across the above-grade portion, anchored to the concrete with two-hole straps at close intervals. I'd use an LB at each end, with a rigid sweep 90 going underground. Transition to PVC below grade after the rigid sweep. I'd use 1"; it's much easier to pull through.

Thanks for all of your help! Yes please chime in anyone else if you agree or have a differing opinion. There for sure won't be vehicle traffic over it, but it will get stepped on quite a bit.

Another question, half of the run is from the main box along the side of the house. There isn't any dirt between house and concrete. The old conduit went underground, which isn't an option. For the above ground conduit that is along house, is it best to run it near the ground, or screw it to the house up a little higher?

mulltron 07-11-2011 08:29 PM

Liquid tite?
 
Hey guys,
Does anyone know anything about liquid tite? Would it hold up outside? I am guessing it might not be code though. I am not getting inspected or anything, but I want to be safe.

mpoulton 07-11-2011 09:07 PM

Liquid tight comes in two types: metallic and nonmetallic. It's not usually used for long runs, only for connections to equipment. It's very easy to work with, but hard to pull through and less durable than PVC.

I'd still say rigid conduit is the way to go for your installation. You could use EMT or PVC for the run along the house, and switch to RMC where it crosses the open pavement. I'd run the conduit along the house just above grade, anchored to the foundation wall or slab edge below the siding.

awdblazer 07-11-2011 09:39 PM

teck90

mpoulton 07-12-2011 01:34 AM

Quote:

Originally Posted by awdblazer (Post 684367)
teck90

Ha! Still not as tough as RMC, and where the heck is he supposed to get just 20-30 feet of that stuff???


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