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Old 11-13-2009, 09:44 AM   #1
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THNN Vs. THWN Wire


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 ?

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Old 11-13-2009, 09:59 AM   #2
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THNN Vs. THWN Wire


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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Old 11-13-2009, 10:11 AM   #3
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THNN Vs. THWN Wire


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.

Last edited by Salem747; 11-13-2009 at 10:15 AM.
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Old 11-13-2009, 10:52 AM   #4
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THNN Vs. THWN Wire


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!
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Old 11-13-2009, 10:53 AM   #5
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THNN Vs. THWN Wire


But the ultimate question, I guess, is: Can THWN be direct buried?
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Old 11-13-2009, 11:02 AM   #6
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THNN Vs. THWN Wire


Quote:
Originally Posted by Salem747 View Post
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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Old 11-13-2009, 11:03 AM   #7
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THNN Vs. THWN Wire


Quote:
Originally Posted by Salem747 View Post
But the ultimate question, I guess, is: Can THWN be direct buried?
NO.
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Old 11-13-2009, 11:05 AM   #8
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THNN Vs. THWN Wire


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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Old 11-13-2009, 12:21 PM   #9
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THNN Vs. THWN Wire


Quote:
Originally Posted by Salem747 View Post
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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Old 11-13-2009, 12:46 PM   #10
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THNN Vs. THWN Wire


Dunno what you mean by "rec" but I ran 3 conductor #6 to the garage.
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Old 11-13-2009, 12:48 PM   #11
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THNN Vs. THWN Wire


3 conductor with ground?
That is what is required in the US
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Old 11-13-2009, 12:52 PM   #12
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THNN Vs. THWN Wire


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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Old 11-13-2009, 12:53 PM   #13
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THNN Vs. THWN Wire


Quote:
Originally Posted by Salem747 View Post
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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Old 11-13-2009, 12:54 PM   #14
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THNN Vs. THWN Wire


Quote:
Originally Posted by Salem747 View Post
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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Old 11-13-2009, 01:07 PM   #15
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THNN Vs. THWN Wire


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/...spectrum_2050/

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

http://www.hypertherm.com/en/Product...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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Last edited by Salem747; 11-13-2009 at 01:10 PM.
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