Why XHHW-2 instead of THHN/THWN?

[M4gery]

It seems like when using aluminum conductors for services everyone uses XHHW-2. That's what all the supply houses want to give you, that's all I've seen other contractors using. I'm just curious why XHHW-2 is the "conductor of choice" for aluminum while THHN/THWN is still the choice when going with copper?

 

[socalelect]

i dont have a real good anwser for this but i can say my local supply house has gotten rid of the XHHW-2 and is now carrying THHN alum,

 

[Howard Burger]

check this thread

check this thread

Try using the forum search for "xhhw thhw". This thread was from awhile ago, and page 2 has some good information.

http://forums.mikeholt.com/showthread.php?t=129867&highlight=thhw+xhhw

 

[augie47]

i dont have a real good anwser for this but i can say my local supply house has gotten rid of the XHHW-2 and is now carrying THHN alum,

I hope it also has a THWN rating also before you use it outdoors or underground.

 

[M4gery]

Try using the forum search for "xhhw thhw". This thread was from awhile ago, and page 2 has some good information.

http://forums.mikeholt.com/showthread.php?t=129867&highlight=thhw+xhhw

I saw that thread and also found other information comparing the two all over the internet. But nothing seems to say why THHN/THWN seems to be the norm for copper while XHHW-2 seems to be the norm for aluminum. Next service I do I'll be sure to ask for THHN/THWN aluminum since it's cheaper.

 

[frankft2000]

Is THHN/THWN sunlight resistant? I know the XHHW-2 I use also says sunlight resistant.

 

[socalelect]

augie, yes it was rated THHN /THWN i havent got any of it yet but i checked it out on the reel its the "simpul" stuff it has a nice slimy feel on the jacked it sshould pull eaiser than the xhhw-2 i was getting

 

[Dennis Alwon]

Is THHN/THWN sunlight resistant? I know the XHHW-2 I use also says sunlight resistant.

I don't believe thhn/thwn is sunlight resistant.

 

[iwire]

You have to check because some is and some is not sunlight resistant.

This from Southwire shows in sizes larger than 2 AWG it is.

http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheetOEM5

 

[electricguy61]

Dang, Bob beat me to it.

[url]http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheetOEM5

G[/URL]ot to get up pretty early to beat a guy with 41,000 posts

 

[kwired]

The OP wondered why XHHW seems to be more common with aluminum conductors than a thermoplastic.

Throughout the thread, and the older thread we had a link to, it has been mentioned the XHHW is a tougher insulation and would be more resistant to cuts, scrapes, etc during installation.

Just from my experience and observations that is a good thing for aluminum conductors especially. You nick a copper conductor it may be in use for years, nick an aluminum conductor and it will fail within months many times, especially in underground raceway that likely will fill with water.

 

[weressl]

It seems like when using aluminum conductors for services everyone uses XHHW-2. That's what all the supply houses want to give you, that's all I've seen other contractors using. I'm just curious why XHHW-2 is the "conductor of choice" for aluminum while THHN/THWN is still the choice when going with copper?

The fundamental difference between the two insulation is that one is thermosetting(XH**) and the other is thermoplastic(TH**). Thermosetting material hardens, while thermoplastic material will soften. So it is more likely that the thermoplastic material will result in the conductors to go to ground or phase-to-phase than the other. Ex. a TH** conductor is touching the enclosure wall and is under tension pressure against it, as it experiences a sustained and uncleared overload the insulation eventually will give and allow the conductor to ground.

 

[kwired]

The fundamental difference between the two insulation is that one is thermosetting(XH**) and the other is thermoplastic(TH**). Thermosetting material hardens, while thermoplastic material will soften. So it is more likely that the thermoplastic material will result in the conductors to go to ground or phase-to-phase than the other. Ex. a TH** conductor is touching the enclosure wall and is under tension pressure against it, as it experiences a sustained and uncleared overload the insulation eventually will give and allow the conductor to ground.

Now that you mentioned the differences in insulation, why is one type more common for aluminum and the other type more common for copper?

 

[Little Bill]

Now that you mentioned the differences in insulation, why is one type more common for aluminum and the other type more common for copper?

This is just my opinion on the subject. The reason I feel that the XHHW insulation/jacket is on the aluminum conductors is the fact that the insulation is tougher and harder to handle. Add copper conductors to that and it would be even harder to handle. Maybe they think the softer alum. conductors will help with the handling of the tougher insulation.

 

[kwired]

This is just my opinion on the subject. The reason I feel that the XHHW insulation/jacket is on the aluminum conductors is the fact that the insulation is tougher and harder to handle. Add copper conductors to that and it would be even harder to handle. Maybe they think the softer alum. conductors will help with the handling of the tougher insulation.

Or maybe it would be too easy to bend the aluminum too sharply causing stress damage to conductor itself.

I really think size of strands has a little more to do with how easy copper or aluminum bends. But I also think copper is more ductile, meaning it can be shaped (bent) without weakening it easier than aluminum can.