TFFN

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oldsparky52

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Wilmington, NC USA
For years I have been of the understanding that all THHN is also THWN and that below #14 the equivalent is TFFN. I just looked at a TFFN reel and it does say gas and oil resistant on it. I did not however see a wet rating. I have used this at gas stations for years (TFFN) in underground conduits. So, have I been in violation all of these years? If something is gas/oil resistant, shouldn't it hold up to water?
 
TFFN, if thats the only marking, is actually a fixture wire(art 402) and as such is not allowed for branch circuit wiring.
 
I thought TFFN or solid TFN was only 16 or 18 for appliances and fixtures.

I have an old piece of a reel in my shop I use for testing things..
 
Had to muddy the water didn't you :)
An "off the top of my head" answer would be "no" but it would be a communication cable and need to be listed under Art 800 which it is not..
(I certainly could be mistaken.)
 
Oh, for data.. does it really matter?

I looked atTFFN. Wet less that 60c, but that’s with 600 volts or less fixture wiring.
 
Hv&Lv said:
Oh, for data.. does it really matter?

I looked atTFFN. Wet less that 60c, but that’s with 600 volts or less fixture wiring.
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Curious, where did you find that (not doubting it, just can't find it)
 
side note: I've seen it used and since it has a nylon jacket never worried about it..but your questioning it makes it interesting.
 
Hv&Lv said:
Oh, for data.. does it really matter?

I looked atTFFN. Wet less that 60c, but that’s with 600 volts or less fixture wiring.
Click to expand...
I see nothing in Table 402.3 that indicates any fixture wire is suitable for wet locations.

I see that there may be products listed as multiple types and some of the other types are suitable for wet locations.
 
That makes sense and is why in post #2 I said IF that was the only marking. With the dual rating of MTW it becomes a 310.104 listed wiring method and suitable for wet locations.
(As far a being used for communications, I will rely on more knowledgeable folks)
 
don_resqcapt19 said:
I see nothing in Table 402.3 that indicates any fixture wire is suitable for wet locations.

I see that there may be products listed as multiple types and some of the other types are suitable for wet locations.
Click to expand...
Same wire, different uses depending on application.
 
augie47 said:
As far a being used for communications, I will rely on more knowledgeable folks)
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I see no reason it couldn't be used for communications. There is no listing for communications conductors.

THHN and TFFN has always been used for things like speaker wiring pulled through pipe. It's the only way to meet Class 1 requirements besides TC.

-Hal
 
As far as I know, THHN, THWN, TFFN, MTW, AWM and so on are all _different_ standards. Meeting one standard does not imply meeting another standard.

While I don't think anyone sells THHN wire that isn't also THWN-2, and so as a practical matter 'all' THHN wire is THWN-2, I don't believe that THHN wire _must_ also be THWN, so somewhere you may be able to get THHN that doesn't also have a wet rating.

-Jon
 
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