# THWN vs THWN-2



## Magnettica (Dec 19, 2006)

What's the difference in insulation besides the columns used for derating? 

I've seen THWN-2 written on large wires like 2/0 copper, but is there such an animal for say #12 copper?


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## 480sparky (Feb 1, 2009)

The difference is obvious in reading T310.13(A).


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## Magnettica (Dec 19, 2006)

Thank you. I should have known it was just a temperature rating. 

THWN is good for a maximum operating temperature of 167ºF and THWN-2 is good for up to 190ºF. 

Thanks again. :thumbsup:


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## JohnJ0906 (Jan 7, 2007)

Magnettica said:


> Thank you. I should have known it was just a temperature rating.
> 
> THWN is good for a maximum operating temperature of 167ºF and THWN-2 is good for up to 190ºF.
> 
> Thanks again. :thumbsup:


Also, the -2 can be derated from the 90° column, where THWN would have to be derated from the 75° column.


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## Magnettica (Dec 19, 2006)

But even still, the 'W' is abbreviated for water, so can the THWN-2 rating be derated from the 90º column if used as an underground conductor in a conduit?


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## JohnJ0906 (Jan 7, 2007)

Magnettica said:


> But even still, the 'W' is abbreviated for water, so can the THWN-2 rating be derated from the 90º column if used as an underground conductor in a conduit?


Yes.

Check out the 310.13(A) table.
THWN is 75°, THWN is 90°.

As a comparison, take a look at THHW. The temp listings change with the location. 90° in a dry location, 75° in a wet location. 

From the looks of 310.13(A), a -2 designation seems to mean that the conductor holds the 90° rating in a wet location, as opposed to dropping from 90° to 75°


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