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Thread: Conductor insulation rating

  1. #1

    Conductor insulation rating

    When did the wiring manufactures stop making a THWN-2 in sizes 10 AWG and smaller. I had an inspector try to make me change the wire on two solar jobs I did cause the wire was dual rated THHN/THWN and it could not run on the roof. I told him that code 310.15 (A)(2) allows me to come out of the attic to my J-Box(AC micros) and less than 3 feet on a 60 foot run. So now if we run wires on the roof exposed to the sun less than 30 amps we need to use a size #8 AWG a 90*C wire. I check the supply house and big hardware stores size 10 AWG and smaller dual rated wire 90*C THHN(dry) 75*C THWN(wet). Am I correct cause on the blue prints I keep seeing #10 THWN-2

  2. #2
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    Quote Originally Posted by elmundogrande View Post
    When did the wiring manufactures stop making a THWN-2 in sizes 10 AWG and smaller. I had an inspector try to make me change the wire on two solar jobs I did cause the wire was dual rated THHN/THWN and it could not run on the roof. I told him that code 310.15 (A)(2) allows me to come out of the attic to my J-Box(AC micros) and less than 3 feet on a 60 foot run. So now if we run wires on the roof exposed to the sun less than 30 amps we need to use a size #8 AWG a 90*C wire. I check the supply house and big hardware stores size 10 AWG and smaller dual rated wire 90*C THHN(dry) 75*C THWN(wet). Am I correct cause on the blue prints I keep seeing #10 THWN-2
    THWN-2 is not made for use outside of a conduit, in this application. Look for USE-2/RHH/RHW-2, or PV Wire.

  3. #3

    It was in the conduit

    Quote Originally Posted by Carultch View Post
    THWN-2 is not made for use outside of a conduit, in this application. Look for USE-2/RHH/RHW-2, or PV Wire.
    This is the feed to the micros on the roof which was ran through the attic and came up to a J-Box next to the array and the Inspector said that it had to be #8 THWN-2 cause they don't make it in #10 or smaller THWN-2 and it has to be a 90* rated insulated conductor for wet location in a raceway like RHW-2, THWN-2, USE-2...... exposed to sun rays. So after going around checking #10 THHN and smaller are 90*C dry and 70*C wet THWN with that being said watch out for your designs and make sure you have the right wire size.

  4. #4
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    Quote Originally Posted by elmundogrande View Post
    This is the feed to the micros on the roof which was ran through the attic and came up to a J-Box next to the array and the Inspector said that it had to be #8 THWN-2 cause they don't make it in #10 or smaller THWN-2 and it has to be a 90* rated insulated conductor for wet location in a raceway like RHW-2, THWN-2, USE-2...... exposed to sun rays. So after going around checking #10 THHN and smaller are 90*C dry and 70*C wet THWN with that being said watch out for your designs and make sure you have the right wire size.
    According to Southwire's products page you are correct. Their #14-#10 is THHN/THWN, THWN-2 doesn't begin until #8 and larger. What was the problem with the 75° C conductor, was it too small after ampacity correction for use on the roof? Under the 2017 NEC if your distance above the roof is 7/8" or greater no temperature adder is required.
    Rob

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    All responses based on the 2014 NEC unless otherwise noted

  5. #5
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    Quote Originally Posted by elmundogrande View Post
    This is the feed to the micros on the roof which was ran through the attic and came up to a J-Box next to the array and the Inspector said that it had to be #8 THWN-2 cause they don't make it in #10 or smaller THWN-2 and it has to be a 90* rated insulated conductor for wet location in a raceway like RHW-2, THWN-2, USE-2...... exposed to sun rays. So after going around checking #10 THHN and smaller are 90*C dry and 70*C wet THWN with that being said watch out for your designs and make sure you have the right wire size.
    #10 THWN-2 not available? I don't believe it. Nearly every datasheet I've ever seen for this type of wire goes down at least as small as #14. The sunlight resistance may be a function of size, as well as color. But the THWN-2 spec applies to all sizes in the family.

  6. #6
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    Quote Originally Posted by Carultch View Post
    #10 THWN-2 not available? I don't believe it. Nearly every datasheet I've ever seen for this type of wire goes down at least as small as #14. The sunlight resistance may be a function of size, as well as color. But the THWN-2 spec applies to all sizes in the family.
    I can't think of a datasheet that does show THWN-2 smaller than #8. Southwire, Anixter, General Cable, Cerro Wire...all #8 and larger for THWN-2.

    There is a logic to the #8 and above cutoff, relating to 240.4(D)...

    #8 THWN-2 has an ampacity of 50 at 75 degrees, but can be derated from 55 Amps.

    #10 THWN can be protected up to 30A, but can be derated from 35 Amps,
    #12 THWN can be protected up to 20A, but can be derated from 25 Amps, and
    #15 THWN can be protected up to 15A, but can be derated from 20 Amps.

    (You would lose that derating ability for circuits that don't fall under the Small Conductor requirements)

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    Quote Originally Posted by david luchini View Post
    I can't think of a datasheet that does show THWN-2 smaller than #8. Southwire, Anixter, General Cable, Cerro Wire...all #8 and larger for THWN-2.

    There is a logic to the #8 and above cutoff, relating to 240.4(D)...

    #8 THWN-2 has an ampacity of 50 at 75 degrees, but can be derated from 55 Amps.

    #10 THWN can be protected up to 30A, but can be derated from 35 Amps,
    #12 THWN can be protected up to 20A, but can be derated from 25 Amps, and
    #15 THWN can be protected up to 15A, but can be derated from 20 Amps.

    (You would lose that derating ability for circuits that don't fall under the Small Conductor requirements)

    Can you explain to me what I'm missing, when I read the following datasheet?
    https://www.encorewire.com/wp-conten...e-THHN-SSE.pdf

    "14 AWG THROUGH 8 AWG: ENCORE*WIRE*CORP*(SIZE)*TYPE*MTW*OR*THHN*OR*THWN-2*GR2*VW-1*600V*(UL)*OR*AWM*OR*C(UL)*TYPE*T90*NYLON*OR*TWN* 75 SUPERSLICK ELITE"

    That seems to state that it is THWN-2 in sizes 14 through 8. What am I missing?

  8. #8
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    Quote Originally Posted by Carultch View Post
    "14 AWG THROUGH 8 AWG: ENCORE*WIRE*CORP*(SIZE)*TYPE*MTW*OR*THHN*OR*THWN-2*GR2*VW-1*600V*(UL)*OR*AWM*OR*C(UL)*TYPE*T90*NYLON*OR*TWN* 75 SUPERSLICK ELITE"

    That seems to state that it is THWN-2 in sizes 14 through 8. What am I missing?
    The "sunlight resistant" marking? The data sheet you referenced adds that marking for sizes above 8 AWG.

    Cheers, Wayne

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    Quote Originally Posted by wwhitney View Post
    The "sunlight resistant" marking? The data sheet you referenced adds that marking for sizes above 8 AWG.

    Cheers, Wayne
    If it is conduit there's no need for it to be sunlight resistant.
    I'll never get there. No matter where I go, I'm always here.

  10. #10

    Raceway of the Roof

    Here in California we just started using NEC 2014. So all I wanted to do is get the word out cause the AHJ are catching on to the #10 conductor insolation for wet location is 75* THWN, but on blue prints its still showing it as THWN-2 and all the math is at 90*C all wrong so be aware before you do and they make you change it out.

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