Conduit for new panels

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  #1  
Old 11-22-06, 08:35 PM
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Conduit for new panels

Need to run 4/0 4/0 4/0 2/0 about 150' and hope someone can tell me what is the smallest size of conduit it's "legal" to run?

At a previous long run at our last home, found it was easiest to lay out the wire and construct the conduit with the wire in it and then trench and lay it in rather than pulling that length.

Want to run conduit because of the depth requirement (36" direct burial and 24" in conduit). Can't find a ditch witch for rent that will go the 36 and want to have no worries come inspection time.

Also going to run 2 - 2 - 2 -4 about 100' aluminum for 100amp to another box. Same question. What size conduit?

Got the impression my local home center fellow was not sure and don't want to dig up those lengths after getting it wrong.

Thanks for any help.
 
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  #2  
Old 11-22-06, 08:40 PM
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4/0 4/0 4/0 2/0 = 2" sch40 is code legal. I'd definitely use 2.5" though.

2 - 2 - 2 -4 = 1.25" sch40 minimum
 
  #3  
Old 11-22-06, 09:19 PM
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Thumbs down Do It Yourself questions.

Originally Posted by hopro
Need to run 4/0 4/0 4/0 2/0 about 150' and hope someone can tell me what is the smallest size of conduit it's "legal" to run?

At a previous long run at our last home, found it was easiest to lay out the wire and construct the conduit with the wire in it and then trench and lay it in rather than pulling that length.

Want to run conduit because of the depth requirement (36" direct burial and 24" in conduit). Can't find a ditch witch for rent that will go the 36 and want to have no worries come inspection time.

Also going to run 2 - 2 - 2 -4 about 100' aluminum for 100amp to another box. Same question. What size conduit?

Got the impression my local home center fellow was not sure and don't want to dig up those lengths after getting it wrong.

Thanks for any help.
MY apoligies for my earlier remark I had my forums crossed up. I had tried to sign in to a code interpretation forum and clicked on this one by mistake.

Conduit cannot be assembled with the wire inside it because the solvent cement will damage the insulation on the conductors which is why the US National Electric Code (NEC) specifically forbids doing so. The maximum depth of bury required by the NEC is 24 inches.

PS if your local home center chap was sure I'd be shocked and amazed.
 

Last edited by hornetd; 11-22-06 at 09:30 PM. Reason: Clarification
  #4  
Old 11-23-06, 12:46 AM
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Speedy's right, a minimum 2 1/2 in. would be easier to work with.

Just an FYI. According to the NEC Table 5 - Dimensions of Insulated Conductors and Fixture Wires, THHN, THWN, THWN-2, 4/0 conductor is approximately 16.31mm or 0.642in. in diameter.

A similar 2/0 conductor is 13.51mm or 0.532in. All together they add up to 62.44mm or 2.458in.

With this in mind, even a 2 1/2 in. conduit seems a bit skinny. Given the tight clearance, 3 in. would be even better - especially on the turns.

Get plenty of conduit lube!
 
  #5  
Old 11-23-06, 06:11 AM
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I think Hornetd made a typo in his post. There is no "maximum depth of bury". He meant to say minimum depth I think.
 
  #6  
Old 11-23-06, 08:44 AM
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Do NOT assemble conduit with wire installed. You will damage the wire.

Replace the previous wire that you installed this way.
 
  #7  
Old 11-23-06, 10:14 PM
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Originally Posted by joed
I think Hornetd made a typo in his post. There is no "maximum depth of bury". He meant to say minimum depth I think.
There may be a better way to say it but the depth of bury required by the US NEC is never more than 24 inches. The OP said he had to bury 36 inches deep so I assume he is dealing with some local requirement.
 
  #8  
Old 11-24-06, 08:53 AM
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I guess it is a matter of interprtation. When I read 'maximum depth of bury" I interpret that to mean you can't bury it deeper than that figure.
 
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