THHN TWN

[bovalex]

I'm alittle confused lately about markings on Wire.
I have in front of me a 10AWG marked THHN 90c / TWN 75c
Is this telling me that i can use THHN in wet location @ 75c, knowing that no equipment is rated @ 90c so you always rate @ 75c. right?
So is this telling that there =

I'd be grateful for explanation. Everyone i ask gives me a different no conclusive anwser.
:?

 

[bovalex]

Ment THWN

Ment THWN

Sorry ment THWN

 

[peter]

The wire we get is labeled "THHN OR THWN". This is because the manufacturer is not sure of what it is manufacturing.
The way I understand it, is that the "T" means Thermoplastic like vunyl.
The "H" stands for heat [75?] and "HH" would be high heat or heat heat [90? Centigrade].
The "N" stands for nylon which is the clear stuff which gets scraped off when when the wire is pulled through mudrings or over the edge of boxes or through Mason conduit bodies.

So you would always use the wire at 75? but in dry locations, you can derate from the 90? column.

~Peter

note: to get the degree symbol, I use Control + 167 on the number pad (num lock must be on).

 

[sandsnow]

Most stuff I see is THHN/THWN-2

The dash 2 gives you 90? See Table 310-13

The degree thing ALT + 167, not control

 

[bovalex]

But every termination on breakers, Air Conditioners,Water heaters, Disconnects etc.. everything is rated for 70c or 60c. So you can't run any wire using the 90c column you have to use the 70c column in 310-13.
thats why i was asking if they are =
I know it's sounds odd, THHN in wet location what will the inspector say, probly nothing, maybe there is no correct answer..


:?

 

[infinity]

But every termination on breakers, Air Conditioners,Water heaters, Disconnects etc.. everything is rated for 70c or 60c. So you can't run any wire using the 90c column you have to use the 70c column in 310-13.
thats why i was asking if they are =
I know it's sounds odd, THHN in wet location what will the inspector say, probly nothing, maybe there is no correct answer..


:?

The conductor that you mentioned in your OP is listed as THHN or THWN. If you use it in a dry location than you can use the 90? rating for derating purposes. If you use it in a wet location than you would use the 75? rating. If it's listed as THWN-2 than you could use the 90 degree rating for derating purposes. There is no 70? column in 310.16.

 

[cormier_paul]

Thhn/Thwn is known as a dual rated wire, it was designed for convenience to be used in both wet and dry locations. Its been along time since manufactures started producing dual rated wire, you have probably been using it for alot longer than you realize. Its almost impossible to get THHN without the THWN dual rating included.