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Old 05-23-2009, 06:20 PM   #1
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conduit coming out of the ground, or exiting building near the ground


I'm sure there's an answer to these two questions somewhere...

1) when conduit emerges from the ground it's got to be rigid or schedule 80 pvc - but how MUCH of it? 12"? 18", more?

2) when conduit emerges from the crawlspace of a building between the sill plate and the floor (thru the joist blocks) at an LB and goes up to a load center and that LB is, say about 15" from the ground, should it be metal/schedule 80 plastic or can it be schedule 40?

Possibly a better way of asking this question: When emerging from the ground or from a structure near the ground with conduit, to what height above ground is it required to be steel or schedule 80 plastic to resist shovel blows, the weed trimmer, the lawn mower, etc?

Thanks in advance,

WM

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Old 05-23-2009, 07:16 PM   #2
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conduit coming out of the ground, or exiting building near the ground


To tell the truth, I don't know the answer for sure, and I'm too lazy to go dig the answer up. However, I have only been required to use Sch. 80 on horizontal runs of conduit that were supported by blocks and not attached to a wall.

I have never used Sch. 80 PVC to emerge from the ground and go up a wall. That said, almost every time I use PVC, it is Sch. 40. I could count on one hand the number of times I've used 80.

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Old 05-23-2009, 08:09 PM   #3
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conduit coming out of the ground, or exiting building near the ground


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Originally Posted by InPhase277 View Post
To tell the truth, I don't know the answer for sure, and I'm too lazy to go dig the answer up. However, I have only been required to use Sch. 80 on horizontal runs of conduit that were supported by blocks and not attached to a wall.

I have never used Sch. 80 PVC to emerge from the ground and go up a wall. That said, almost every time I use PVC, it is Sch. 40. I could count on one hand the number of times I've used 80.
Innnteresting. I wonder if that requirement is just to deal with sch. 40 sagging in the sun/heat. I know for sure LA inspectors are worried about how much of the emerging raceway could get sliced with a shovel or a weed trimmer because a few years back my next door neighbor redid his small 4-plex apartment building and somewhere around final got dinged for 4 conduits emerging and running up to a wall mounted outlet and light in the side yard/patio space for each unit just outside their sliding glass doors. They replaced Sch. 40 with Sch. 80 up to the outlet, then left the rest Sch. 40.

My question is specific to the 2nd variation of the question in my original post as that's the condition i've got in my install.

Thanks,

WM
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Old 05-23-2009, 08:23 PM   #4
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conduit coming out of the ground, or exiting building near the ground


it also has to do with what kind of possible damage the conduit would be exposd to. If it is in a vulnerable area, sch 80 would be required. If not, 40 is fine. Service entrance cables subject to damage is but one place 80 is required over 40. NEC '05 230.50(A)

where the conductors exit the ground and are running up a pole, 80 us required as well to a point at least 8 feet up. NEC '05 300.50(B)

the simple rule is that is that if the conduit is subject to damage, it must be sched 80 (ya, simple, like "subject to damage isn;t interpretable by the AHJ in a lot of odd ways)

and yes, the weed whacker is judtification for using 80.
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Old 05-23-2009, 08:38 PM   #5
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conduit coming out of the ground, or exiting building near the ground


Any height. If you are coming out of the ground against a wall, Sch. 40 should be fine to any height. If you are wanting more protection, skip the 80 and go straight to rigid conduit.
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Old 05-23-2009, 08:48 PM   #6
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conduit coming out of the ground, or exiting building near the ground


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Any height. If you are coming out of the ground against a wall, Sch. 40 should be fine to any height. If you are wanting more protection, skip the 80 and go straight to rigid conduit.
it's not about me wanting protection, it's about a city of LA inspector insisting on protection. :P

i have 4 1" plastic runs that emerge from under the house between the sill plate and the floor (thru where a joist block would go) and need to turn upwards to the load center right above them. They pop out about 16" from the ground above a short stem wall. I think I've decided to connect the 1" sch. 40 runs to a glue on/screw in coupler, screw on a metal LB pointed up, screw a raintight EMT compression coupler to that, and go EMT up to the box. I just finished today bolting on shallow superstrut and hanging the box.

Now if I can just get it all to hit knockouts with 1" nipples and such as I certainly won't be bending my own offsets out of 1" EMT I don't think...

Further comments are always appreciated.

WM

Last edited by wmldwilly; 05-23-2009 at 08:49 PM. Reason: forgot stuff
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Old 05-23-2009, 09:50 PM   #7
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conduit coming out of the ground, or exiting building near the ground


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Originally Posted by wmldwilly View Post

Now if I can just get it all to hit knockouts with 1" nipples and such as I certainly won't be bending my own offsets out of 1" EMT I don't think...



WM

why not? I do it all the time. I do not know how long of a pipe you are dealing with nor how much offset you may need so I cannot speak to your situation directly though.
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Old 05-24-2009, 01:58 AM   #8
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conduit coming out of the ground, or exiting building near the ground


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why not? I do it all the time. I do not know how long of a pipe you are dealing with nor how much offset you may need so I cannot speak to your situation directly though.
After I wrote that I started thinking about it and thought next week I'll ring up my favorite wholesaler and order a 1" bender (i've only got little ones) and the 1" emt I need for this and the rest of the project and go for it. I'm so used to the big box stores not carrying anything more than 3/4" of everything...then on a trip this evening for a few supplies to a brand new big box home center that opened nearby (it's nice when they're new and not destroyed and picked clean by the crazy unlicensed contractor and "handyman" crowd in this particular big city...) LO and behold - EMT stocked all the way up to 3", and Klein 1" benders. Soooo, I retract my previous statement - i'll make my own 1" offsets to fit my application.

WM
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Old 05-24-2009, 02:35 AM   #9
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conduit coming out of the ground, or exiting building near the ground


Ever heard of flex?



The requirement for conduit other than PVC stubbimg up is regional AND open to interpetation (subject to damage). Flex can work nicely for that last bit when terminating conduits into panels.
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Old 05-24-2009, 03:14 AM   #10
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Ever heard of flex?

The requirement for conduit other than PVC stubbimg up is regional AND open to interpetation (subject to damage). Flex can work nicely for that last bit when terminating conduits into panels.
uh...yea. heard of flex. can't get enough of the stuff.

My interactions with my inspector so far lead me to believe that for this part of the install (exterior/surface, in a 5'0" side yard) he's not going to buy little 12" stubs of LFMC out of the bottom of the load center (yes, it's NEMA 3r) taking the place of bends or regular fittings connecting to EMT going down and under the house. I'd LIKE to do it that way because frankly the knockout pattern at the bottom of the brand new box is kinda wacky and doesn't neatly land the 4 evenly spaced conduits that come out from under the house, but local licensed guys tell me i'd raise the inspector's eyebrows less if I just avoid plastic or coated flex at all where it's exposed from the bottom of the box down to the LBs & runs under the house. As one friend says "no matter who or what runs a wheelbarrow or weed eater into it, no matter what blows rain on it or splashes it or who sprays it with a hose it's dry and not breakable".

If y'all think i'd be totally fine doing it as above let me hear it it because it'd be easier for me for sure. Should I want to back this up with some of those fancy numbers with dots and little letters in parentheses after them?

WM

Last edited by wmldwilly; 05-24-2009 at 03:16 AM. Reason: typo
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Old 05-24-2009, 04:44 AM   #11
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conduit coming out of the ground, or exiting building near the ground


Ask him for the code reference when he turns it down.

Or, call his boss or another inspector. The term is "subject to damage" and is wide open to interpetation.

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