UF cable in conduit

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  #1  
Old 07-18-05, 04:27 PM
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UF cable in conduit

I am installing 10/3 w/grnd UF cable underground from a sub-panel in my basement to an outbuilding. I am burying it between 12 and 18 inches below ground level (protected by 20 amp breaker) except where I go over exposed rock ledge in which case I protect it with PVC conduit. I need to use approx. 35 feet of conduit. Should I be concerned that the UF cable is not intended for conduit and may heat up?

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  #2  
Old 07-18-05, 09:11 PM
Eggroll
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I don't see anything wrong with it. I'm probably wrong by the perfect world standards, but in the real world... i'd put the UF cable in the PVC and let it be.
 
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Old 07-18-05, 09:16 PM
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You don't have to worry about overheating this wire in this installation, unless there are external issues, eg. a location that naturally gets _very_ hot. There may be other mechanical issues with this installation; I don't know all of the details.

-Jon
 
  #4  
Old 07-18-05, 09:51 PM
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Only thing to add would be that you probably would be required to use sch. 80 pvc in this application.
 
  #5  
Old 07-18-05, 09:59 PM
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some of you code savvy guys correct me if i'm wrong...

NEC states burial depths of raceways to be 24" for pvc, 18" for emt, 12" for IMC, and 6" for rigid. I would assume UF would need to be at least 24" deep. Though I have had an inspector tell me when I ran a pool circuit and I quote "120 volts in a residential backyard, 16 to 18 inches will be fine." Since I had a trencher, I put it at about 30 inches anyway.
 
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Old 07-18-05, 10:05 PM
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Direct burial needs to be 24" by code (with some exceptions), if your using a trencher then it is a perfect world if your digging it with a shovel then many times the perfect world starts slipping away.
 
  #7  
Old 07-19-05, 08:33 AM
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Direct burial 24" (with some exceptions that don't apply here). PVC 18". Rigid 6".
 
  #8  
Old 07-19-05, 04:23 PM
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Thanks for your comments.

I was not expecting the burial depth to be disputed. My reference books on electrical wiring (the latest based on 1996 NEC) say that in residential wiring UF can be buried a minimum of 12Ē provided the cable is protected by a breaker of 20 amps or less and protected by a GFCI. Is use of GFCI one of the exceptions noted in a couple of the above posts OR do I need more up-to-date books?

Actually, Iíve NOT been corrected by the building inspector previously for burying UF 12Ē-18Ē, even without a GFCI, but then again inspectors canít check everything.

If anyone can clarify this point it would be appreciated. It donít look forward to digging any deeper than required in this Connecticut glacial till.
 
  #9  
Old 07-19-05, 08:08 PM
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The 12" burial depth is only allowed for "branch circuits". Your cable is a "feeder", not a branch circuit.
 
  #10  
Old 07-20-05, 12:04 PM
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John

I understand now. Thanks for your help.
 
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