# THNN Vs. THWN Wire



## indy (Nov 9, 2009)

I went to Home Depot and Lowes for THWN wire for outside wiring in a conduit. They only carry THNN wire.

Should I use THNN or THWN ? I heard THWN is for wet locations like outside conduits. Where Can i buy this wire ?

Thanks


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## Scuba_Dave (Jan 16, 2009)

THWN has to be used in conduit outside
A lot of the THHN is also rated as THWN
They may only advertise it as THHN, you need to check the wire
Or go to a real electric supply


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## Salem747 (Oct 16, 2009)

Isn't THWN (thermoplastic high water resistant nylon) rated for direct burial? THHN is thermoplastic high heat resistant nylon. THNN is for damp locations not direct burial. 

If you look at the wire and read the marking on the side it will say what it actually is, as you can imagine people get these acronyms mixed up. 

Also sometimes it will be rated for more than one of these spec ie both THWN and THHN.


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## kbsparky (Sep 11, 2008)

Most THHN is also dual rated as THWN and MTW. It may also have a suffix rating of -2, such as THHN-2 THWN-2 etc.

Look at the actual piece of wire, betcha all those ratings are printed on it! :whistling2:


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## Salem747 (Oct 16, 2009)

But the ultimate question, I guess, is: Can THWN be direct buried?


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## jerryh3 (Dec 10, 2007)

Salem747 said:


> But the ultimate question, I guess, is: Can THWN be direct buried?


No. It must be in a conduit or in an approved direct burial jacket.


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## kbsparky (Sep 11, 2008)

Salem747 said:


> But the ultimate question, I guess, is: Can THWN be direct buried?


NO.


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## Salem747 (Oct 16, 2009)

My home Despot sells direct burial cable that is in a black jacket. That's what I used for the garage, inspector had no problem with it. I assume that it is the THWN then. I wasn't thinking of loose wire but is the guy asking the question thinking loose wires or like a 3 conductor like I used???


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## 300zx (May 24, 2009)

Salem747 said:


> My home Despot sells direct burial cable that is in a black jacket. That's what I used for the garage, inspector had no problem with it. I assume that it is the THWN then. I wasn't thinking of loose wire but is the guy asking the question thinking loose wires or like a 3 conductor like I used???


 Is this a sub panel in the garage if so you need to have 4 wires and seperate the ground and nuetral Or did you just run some rec to garage?


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## Salem747 (Oct 16, 2009)

Dunno what you mean by "rec" but I ran 3 conductor #6 to the garage.


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## Scuba_Dave (Jan 16, 2009)

3 conductor with ground?
That is what is required in the US


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## Salem747 (Oct 16, 2009)

Yes. 2 "blacks" 1 white and a bare ground. In Canada the ground for the sub has to be carried back to the main panel.

There was another guy on here that was doing a sub-panel and just installing a new ground at the sub, that wouldn't float in Canada.


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## 300zx (May 24, 2009)

Salem747 said:


> Dunno what you mean by "rec" but I ran 3 conductor #6 to the garage.


receptacle(outlet) or did you put in a sub panel 3 #6 here would not pass inspection here you also need a ground and a few other things if this garage is detached!!!


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## 300zx (May 24, 2009)

Salem747 said:


> Yes. 2 "blacks" 1 white and a bare ground. In Canada the ground for the sub has to be carried back to the main panel.
> 
> There was another guy on here that was doing a sub-panel and just installing a new ground at the sub, that wouldn't float in Canada.


 Sorry you posted before me.


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## Salem747 (Oct 16, 2009)

Yeah, with my welder and stuff I wanted 60A in the garage, I installed a 100A Cutler-Hammer panel (In the US it might be Eaton), on a 60A breaker in the main panel. It is detached. I'm kicking myself a bit though, I put in a 30A circuit for my welder, put up the walls and then found a great deal on a use Miller 40A plasma cutter!!!

http://www.millerwelds.com/products/plasma/spectrum_2050/

I decided to go with a new, smaller one that can run on 110V and 220V.

http://www.hypertherm.com/en/Products_and_Services/Manual_Plasma/powermax30.jsp

It might be a touch underpowered for some bigger stuff I may do sometime in the future but I like the 110V capability and the bigger ones are all 220V only.

Now that is a cool tool!!!

Now I kinna wanna leave work early to go home and play with it!!!


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## micromind (Mar 9, 2008)

I realize this is sort of late in the thread, but here's what the wire designation letters mean.

T=Thermoplastic insulation, 60C

H=15C higher. HH=30C higher.

W=Wet locations. Ok to submerge in water. The inside of a conduit installed in a wet location is considered a wet location. 

N=Nylon outer covering.

THHN=90C insulation, dry locations only.

THWN=75C insulation, OK for wet locations.

Be careful with the 90C temperature rating though, the vast majority of terminations are rated for a maximum of 75C, and this is the ampacity column you must use in table 310.16 The 90C rating is useful when de-rating due to multiple conductors in the same conduit. 

Rob


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