Trenching for outdoor direct burial wire

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  #1  
Old 07-08-11, 04:35 PM
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Trenching for outdoor direct burial wire

Hi there,

I am going to rent a trencher in order to bury some direct burial cable and run it out to power a pond aereator and pump for the sprinkler system. My question is this....

I would also like to run about 100' of corrugated pipe that ties into my gutters and runs the rain water into the pond where I am sending the electric. Can I bury both of these in the same trench or do I need two trenches? I know burying water with electric sounds crazy, but it is direct burial wire. What if I run the corrugated pipe down about 24", then cover with a bit of dirt, then bury the direct burial electric wire at 18" ? This way if I need to dig out and access the electric wire I will not need to dig through the corrugated pipe first.

Any thoughts?
 
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Old 07-08-11, 05:15 PM
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then bury the direct burial electric wire at 18"
UF can be buried as shallow as one foot if the voltage is 120v, amperage no more then 20a and a GFCI breaker is used otherwise the minimum depth is 24".
 
  #3  
Old 07-08-11, 05:55 PM
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Your idea would probably work fine but I would certainly put the wiring in PVC conduit. You're going to that much trouble to dig the trench and everything else so why not just put in the conduit to avoid any future problems?
 
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Old 07-08-11, 06:46 PM
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Note if you use conduit you would normally use individual THWN conductors not UF.
 
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Old 07-08-11, 09:30 PM
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When I put in a storm sewer years ago, I figured I would just throw everything but the kitchen sink in that trench. I had a large roll of 12/3 UF leftover, as well as some HDPE innerduct. I bought 160 psi NSF PE pipe for irrigation in case I ever want to add that. The minimum burial depth of my UF cable is 24", with the corrugated 4" storm pipe running directly below that. The maximum depth is about 44".

The 12/3 could be used for 120 or even 240 VAC, but I am currently using a bit of it only for landscape lighting. The innerduct could carry any low-voltage ... I was thinking irrigation control, cable TV, maybe data to the garage. Right now I am just using the phone line to the garage.

Backfill to six inches below the surface and then lay in a "CAUTION" tape or whatever. Also there are a few stubs that do not have the 12/3, and in those I direct-buried scrap 12 AWG in case I need a locator some day.
 
  #6  
Old 07-09-11, 03:07 PM
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Thanks

Thanks for the info. I think I will try to get to 24 " for the UF line, with the storm corrugated pipe below that by 6" or so. I like the advice of going with the yellow caution tape about 6" below grade in the trench. Also- to ARGMEMATEY- did you put teh 160 psi NSF pipe for your sprinkler in the same trench? If so- how far on top of the UF line buried at 24 " deep did the sprinkler line go? How far does the sprinkler line need to be? That would be great if I can go in the same trench with that....
 
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Old 07-10-11, 03:46 PM
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As long as the UF wire is buried to at least the correct depth (12" if on a GFCI breaker; 18" if non-GFCI). There's no requirement for it to be separated at all from other piping or wiring. I personally wouldn't bother digging down 30" for the wiring or drains, unless you really need to dig that deeply for the correct drainage pitch. Then again, you might have soft soil to make it easy. I tend to dig into rocks around here.
 
  #8  
Old 07-10-11, 03:58 PM
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Originally Posted by noake View Post
I will try to get to 24 " for the UF line, with the storm corrugated pipe below that by 6" or so. I like the advice of going with the yellow caution tape about 6" below grade in the trench. Also- to ARGMEMATEY- did you put teh 160 psi NSF pipe for your sprinkler in the same trench? If so- how far on top of the UF line buried at 24 " deep did the sprinkler line go? How far does the sprinkler line need to be? That would be great if I can go in the same trench with that....
The reason my stuff was 24" deep at minimum was because my gravity storm system required the inlet at about two feet below grade. That it happened to be 24" deep for the UF was just coincidence. I wouldn't dig that deep unless required.

Yes, everything is in the same trench. The corrugated pipe on the bottom, and directly on top of that, the innerduct, UF, and HDPE pipe are side-by-side. But if depth is an issue, I don't see why you couldn't put the UF on the bottom, as long as you're not lining the trench with rock.
 
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