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Old 03-13-2008, 03:02 PM   #1
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burying wire underground


i am about to run some wire underground from my basement to a prospective shed. if i am burying wire, can i just use a regular DWV PVC pipe to run it inside or do i need to use special conduit pipe (grayish color). what the heck is the difference between the two ?

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Old 03-13-2008, 03:27 PM   #2
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You cannot use the type DWV pipe, it is not listed for use as an electrical conduit.

The DWV fitting will not have the same radius to allow wires to be pulled.

Make sure your glue is dry before pulling your wires in. Your individual conductors will need to be rated THWN for the wet environment.

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Old 03-13-2008, 03:47 PM   #3
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burying wire underground


thanks.

the conduit will contain two gauge 14-2, one 12-2, and one 10-3 (i want a 240/120V outlet in the shed for a stick welder). which diameter conduit do you think i should use to be able to run them comfortably without tightness.

i will first dig under the foundation to protrude the conduit on the other side perhaps a foot or so beyond the wall on the other side. some time later, i will dig on the other side and actually pull the cables through. i am doing it now on the inside because i have the concrete lifted up (dropping basement floor). i plan to the first phase of the conduit to be L-shaped where the horizontal line goes from the inner to the outer side of the wall and the vertical line goes from the inner side underground to just above the floor right next to the wall. will i be able to get a conduit elbow that bends widely to smoothen the shoving of the wires in ? a typical sharp elbow would be hard to maneuver the turn, even with a fishtape.

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Old 03-13-2008, 03:59 PM   #4
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You cannot do what you propose. You may run ONE circuit, either 120v or 240v to another building. You may not run multiple circuits from one building to another. Consider a 40 or 50a feeder to a subpanel in the shed, then branch circuit your 14/2's and 12/2's from there.
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Old 03-13-2008, 04:28 PM   #5
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burying wire underground


cool. if i go with a 40 A feeder and a subpanel, what size conduit pipe should i use ? also, do they have wide-bending elbows to ease shoving the feeder in after the conduit has been installed (see above) ?

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Old 03-13-2008, 05:57 PM   #6
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What you want at the foundation penetration is called an "LB". You remove a cover to pull the wires into the conduit.

http://electrical.hardwarestore.com/...-entrance.aspx
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Old 03-13-2008, 06:05 PM   #7
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yeah but this is a sharp right angle, i will have a hard time fishtaping the feeder through it after the fact (it will get buried, then concrete poured over). i will not have the luxury to maneuver the cable by hand immediately around the LB. i need a wide-bend elbow, much like a 4 in toilet drain pipe needs where it turns horizontal to make the turn more gradual.

think of pushing a cable through a J rather than an L.

see what i'm saying ?

thanks,

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Old 03-13-2008, 06:38 PM   #8
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Originally Posted by amakarevic View Post
yeah but this is a sharp right angle, i will have a hard time fishtaping the feeder through it after the fact (it will get buried, then concrete poured over). i will not have the luxury to maneuver the cable by hand immediately around the LB. i need a wide-bend elbow, much like a 4 in toilet drain pipe needs where it turns horizontal to make the turn more gradual.

think of pushing a cable through a J rather than an L.

see what i'm saying ?

thanks,

- a -
You cannot do that. All pull points in the raceway must be accessible. Your conduit run must be designed to accomodate the wire installed inside it, as well as servicing it inspecting it and accessing it and possibly replacing it if needs be. You can't run an electrical conduit as though it was a water pipe. The parts called sweeps are not tight, they're gradual. Sharp turns are done with elbows with removable, accessable covers.
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Old 03-13-2008, 07:35 PM   #9
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burying wire underground


I don't think he's planning on encasing any access point in concrete. He's just wondering if there are 90 degree elbows for conduit that are gradual. The answer is that ALL elbows are gradual for conduit because they're designed to pull cable through. LBs are exceptions (pictured above) and they are placed where you want a sharp 90 degree turn, or in the middle of long runs which require more than 360 degrees total bends in the conduit. To pull at LBs you take off the cover, and pull the wire out, then feed it into the other end.

You must design your conduit run with less than 360 degrees of bends between pulling points.
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Old 03-13-2008, 08:27 PM   #10
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burying wire underground


To run a 4 wire feeder to the shed you can use #8 copper wire for a 50 amp circuit or #8 aluminum for a 40 amp circuit. Use type thwn or xhhw wire. You can use a #10 copper or #8 aluminum wire for the ground. The four conductors need a minimum of 3/4" sch 40 PVC conduit, but I would recommend using 1". Use the standard or the long radius sweep elbows for ease of pulling and for burying them with no access required. Use the grey electrical conduit as mentioned above. Install the correct size 2 pole circuit breaker in your house panel for the wire used, and install a sub panel in the shed with a main circuit breaker for a disconnect. You will also need a ground rod at the shed connected to the ground bus. The grounds and neutrals in the shed will be kept separate from each other. Check your local codes also.
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Old 03-13-2008, 09:43 PM   #11
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Quote:
You cannot do what you propose. You may run ONE circuit, either 120v or 240v to another building. You may not run multiple circuits from one building to another


Get the flip outta here.....really?


Can I get a code reference?
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Old 03-13-2008, 10:27 PM   #12
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Originally Posted by 220/221 View Post
Get the flip outta here.....really?


Can I get a code reference?
225.30, but part (A)-(E) have exceptions...
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Old 03-13-2008, 10:58 PM   #13
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Originally Posted by chris75 View Post
225.30, but part (A)-(E) have exceptions...
Says the same thing in my book.

Of course some people don't need no stinking codes.

Accept that as humor if you would 220. I just couldn't resist.
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Old 03-13-2008, 11:44 PM   #14
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Hey, I try to learn something new every single day.


I even learned something from Petey one time.



(D) "shall be permitted for different voltages" seems to say that I can run a 240 for a welder and a couple of 120 circuits if they share a neutral.

(E) says something about "documented safe switching proceedures". I'll look that up in the unlikely event that I want to run multiple circuits to an outbuilding.

I don't recall ever running multiple circuits to a separate building. It makes more sense and is a better installation to install a sub and that's why I have always done it.

I never knew it was illegal to install multiples.
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Old 03-14-2008, 01:28 AM   #15
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Quote:
Originally Posted by 220/221 View Post

I never knew it was illegal to install multiples.

C'est true it been written for long time and it the same thing in European regulations as well.

Merci, Marc

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