conductor rating in RNT

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Woodyz

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When sizing wire ran in PVC does 352.12(d) & (e) more or less say we must use 60 c column of 310.16 + a little when ran anywhere other than in a trench or 10' before and after.

Ref's from 02 book
 

infinity

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Not sure that I understand your question. The two sections that you've posted are in regards to the ambient temperature in which the conduit is installed and the operating temperature of the conductors.

352.12(D) tells you that the conduit would need to be rated for ambient temperatures above 122 degrees and (E) tells you that the conductors inside cannot operate at a temperature that exceeds the conduits' operating temperature rating.
 

Woodyz

Member
I guess what I'm asking is do I need to run a #6 for a 40 amp circuit since a #8 tw at 40 amps would be 60 degree c which would exceed the 50 degree c of the pvc. Or are the 2 items treated seperatly.
 

celtic

Senior Member
Location
NJ
352.12
D) Ambient Temperatures.
Where subject to ambient temperatures in excess of 50?C (122?F) unless listed otherwise...
(Added bold for empasis...and my spelling is bad :) )


2.0 Product Requirements:
Conduit shall be Carlon Plus 40, rated for use with 90? C conductors, UL Listed or approved equal.

5.0 Product Requirements:
Conduit shall be Carlon Plus 80, rated for 90? C conductors, UL Listed or approved equal.
http://www.carlon.com/
http://www.carlon.com/Specs/Spec-Sch40_80.pdf
 
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infinity

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The ambient temperature is the temperature of the air or material around the conduit and not the operating temperature of the conductors within the conduit. If the conduit had a temperature limit of 90 degrees C you technically could use a 90 degree C conductor operating at 90 degrees C. All other issued aside.
 

infinity

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Woodyz said:
I guess what I'm asking is do I need to run a #6 for a 40 amp circuit since a #8 tw at 40 amps would be 60 degree c which would exceed the 50 degree c of the pvc. Or are the 2 items treated seperatly.


Just curious why you're running TW conductors?
 

celtic

Senior Member
Location
NJ
Related question...all other issued aside...
THHN is listed in the 90? col.
THWN is listed in the 75? col.

Aren't they dual rated(THHN/THWN)?
Which col. do you use ~ 90? or 75??
 

iwire

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Location
Massachusetts
celtic said:
Related question...all other issued aside...
THHN is listed in the 90? col.
THWN is listed in the 75? col.

Aren't they dual rated(THHN/THWN)?
Which col. do you use ~ 90? or 75??


In a wet location 75

In a dry location 90

BUT.... if it is "Type 2" it can used at 90 C wet or dry.

Most THWN/THHN is actully THWN/THHN-2


Clear as mud...:grin:
 

celtic

Senior Member
Location
NJ
iwire said:
The "Type 2" info can be found in Note 4 of Table 310.13.

Not a place that it's likely to be seen.

"1000 things not likely to be seen in the NEC" ...think we can get George to make a FAQ?
 
iwire said:
In a wet location 75

In a dry location 90
:

I always found this interesting..but didnt put too much thought into it..

Seems like "wet" would cool the insulation down. Does anyone know why wet is lower?
 

Woodyz

Member
Sorry boys been away awhile. No intentions of using tw. Just a hypothetical situation I thought of while reading "the book". Thanks for replies, your views appear the same as mine.
 
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