uf-b in conduit on roof

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  #1  
Old 10-25-14, 10:48 PM
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uf-b in conduit on roof

Is it allowed? It seems to have same specs as thhn.
 
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Old 10-26-14, 12:47 AM
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THHN* can't be used in wet locations but THWN can be. UF-b is allowed in conduit but harder to work with. Do you have a reason for not using THWN?

Almost individual wire is dual rated THHN/THWN.
 
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Old 10-26-14, 12:53 AM
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I looked at THWN and didn't like the single wire method. UF-B cable comes in set of 8/2 and ground. I was planning to use for solar project after microinverter to panel etc.. Can this cable be installed in a conduit on the roof?

I kinda ordered some and need to know if I should cancel.
 
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Old 10-26-14, 04:44 AM
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If you have many bends, you will find it difficult to push/pull through the conduit. What size conduit are you planning? EMT, PVC? Are you terminating in junction boxes on the roof? Without the sheathing, the individual wires will be much easier to pull through the conduit.
 
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Old 10-26-14, 06:05 AM
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You will need a very large conduit since the sizing is based on the width of the cable, not just what it will fit in.

Also the conductors will need to be derated if not above the roof by 4" or more.
 
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Old 10-26-14, 07:54 AM
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I would definitely go either UF-B or THWN in conduit. While it is code-compliant to pull UF-B in conduit, it's a pain, and close to impossible with more than one or two elbows. Add in how difficult it is to strip, I'd go with conduit and THWN in many cases.

I"m assuming you need to run the wire from your basement, up the side of the house, along the roof, to the panels. You could of course do it in UF-B only, but that would look messy. You'd probably need 1" or 1.25" PVC to be able to pull 8/2 UF-B.

Code wise, you could fit those same three 8ga THWN wires in a 1/2" conduit (though I would probably upsize to 3/4" for ease of pulling.
 
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Old 10-26-14, 12:37 PM
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Thanks for the replies. I didn't research the sizing of the physical wire. I think i will go with THWN through 3/4" pvc. Hope I can still cancel the order for UF-B wires.

Edit:

I do notice a lot places list the THHN with THWN-2 usage and some lists only THHN. But looking at the wire part number, the mfg states THWN-2 usage too. Is there such a thing as THHN wire only?
 

Last edited by tongsama; 10-26-14 at 01:24 PM.
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Old 10-26-14, 01:40 PM
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Is there such a thing as THHN wire only?
Somewhere probably but since you can use THWN anywhere THHN is used and the only difference, if any, is the insulation probably isn't worth the effort to make and market THHN.
 
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