# Service conductors in underground conduit for 200A



## UpNorth (May 17, 2007)

I'm buying all the materials, and a qualified sparky will do the work. 

I know the wire size to be, if aluminum, 4/0-4/0-2/0, but what spec should the wire be? And is it less expense to use a full-jacket URD-type or separate XHHW wire?

I'm told that there need be no ground, that only the phase and neutral conductors will be in the sch80 PVC conduit, and that grounding will be at the panel.

Your comments are appreciated.


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## aptpupil (Jun 12, 2010)

UpNorth said:


> I'm buying all the materials, and a qualified sparky will do the work.
> 
> I know the wire size to be, if aluminum, 4/0-4/0-2/0, but what spec should the wire be? And is it less expense to use a full-jacket URD-type or separate XHHW wire?
> 
> ...


around here i think it's more common to use separate thhw-2 wire.
what are the advantages of xhhw over thhw? x is basically pex (crosslinked polyethelene) sheathing, right? i think both are ok around oil/gas. other differences?


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## woodchuck2 (Feb 27, 2008)

Depends on where you are and your local codes but here we can longer put any sheathed cable in conduit so we use Alum. URD Triplex.


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## UpNorth (May 17, 2007)

Thanks, Woodchuck. Is your inspector able to cite the code ref that spells out URD being required in NMT for underground service? Because I am unable to find that in my NY Residential Building Code, 2010 edition.

Does your supply house sell you cut lengths needed for something like Southwire URD triplex alum 4/0-4/0-2/0 "Sweetbriar," or does the supply house require you to buy in bulk 1000' coils?

Edit. Sparky gets back and says inspector will take either the URD in conduit or separate conductors at proper spec. Local supply houses confirm they'll cut and sell what is needed. Just a matter of comparing a few numbers. The feed-thru panel we come out of was serviced by the POCO with separate conductors. Done.


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## woodchuck2 (Feb 27, 2008)

If i remember correctly the inspector stated it was a POCO requirement. This just changed several yrs ago when we went from Niagra Mohawk to National Grid.


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