Ambient temperatures within raceways above rooftops

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ActionDave said:
Wow. How cool. Rooftops get hot. Who knew?

Good thing the Copper Development Assc. has a chart to tell us how to know how much more copper we need to use for rooftop installations.
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Got 3 things out of your comments -- you know the formula for 2% design, you don't care, or you don't derate. FYI, answers a a good thing when tradesmen ask questions prior to install.
 
The study was funded by the copper association and there is no history of cable failures on roof top installations to back up the copper associations study. It appears to me and many others that the study is just aggressive marketing.
 
don_resqcapt19 said:
The study was funded by the copper association and there is no history of cable failures on roof top installations to back up the copper associations study. It appears to me and many others that the study is just aggressive marketing.
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Kind of blows a hole in all ampacity adjustment procedures then doesn't it? If it is heat that is supposed to degrade the conductors, why are they not failing on these rooftops where the temp's are fairly extreme sometimes?
 
kwired said:
Kind of blows a hole in all ampacity adjustment procedures then doesn't it? If it is heat that is supposed to degrade the conductors, why are they not failing on these rooftops where the temp's are fairly extreme sometimes?
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Very good point.
I wonder if the exception for XHHW in 310.15(B)(3)(a)(5)(c) will be extended to other derating applications?
 
Smart $ said:
We all know you mean 310.15(B)(3)(c) Exception. There is no exception to 310.15(B)(3)(a)(5)(c).
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That's what I get for trying to follow the code sections in the electronic version of the handbook. The commentary gets in the way of following the sections...I knew I should have looked at my hard copy of the code itself....
 
don_resqcapt19 said:
That's what I get for trying to follow the code sections in the electronic version of the handbook. The commentary gets in the way of following the sections...I knew I should have looked at my hard copy of the code itself....
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I don't use the handbook very often, but I see what you mean. The indentation for 3rd level subordinates (parenthesized lower-case alphabetic) is greater than 4th level subordinates (parenthesized numeric). Indentation, when used, should increase with level.
 
Smart $ said:
I don't use the handbook very often, but I see what you mean. The indentation for 3rd level subordinates (parenthesized lower-case alphabetic) is greater than 4th level subordinates (parenthesized numeric). Indentation, when used, should increase with level.
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I only have the handbook in the electronic version. My code book is out in the truck and usually am too lazy to go look at it. I need a way to view the electronic handbook without seeing the commentary text, but I don't know how to do that.
 
don_resqcapt19 said:
I only have the handbook in the electronic version. My code book is out in the truck and usually am too lazy to go look at it. I need a way to view the electronic handbook without seeing the commentary text, but I don't know how to do that.
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Is that electronic version a PDF version, that appears to be the only way they offer the handbook in an electronic format.
I happen to have the standard 2014 NEC in the "E-book" version. It doesn't have all the handbook commentary but does have some explanations of changes at times which is convenient at times. Whenever another section is referenced that reference is a link to the mentioned section just like in the old CD ROM versions of older codes. You also access it with a username and password -bad news is it won't work offline, but good news is it works from any browser, with your username and password.
 
mwm1752 said:
Got 3 things out of your comments -- you know the formula for 2% design, you don't care, or you don't derate. FYI, answers a a good thing when tradesmen ask questions prior to install.
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On the other hand it takes no skill whatsoever to over design a system. All it takes is a willingness to freely spend other people's money.
 
Funny how this group strays from the obvious -- Up until the 2014 NEC there was no exception to XHHW-2 and the value of the link was intended to coincide with 2009 ASHREA so that one could find the design temp for their area. The chart does nothing more than combine Table 310.15(B)(2)(b) row for ambient temp and 310.15(B)(3)(c) in order to simplify the appropriate correction factor to use. I apologize for assuming some would find value in it's content. I mean no political support of a self serving organization.
 
don_resqcapt19 said:
... I need a way to view the electronic handbook without seeing the commentary text, but I don't know how to do that.
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I don't believe it is possible. If you want to view current edition [2014], you can use the online NEC Public Input... but to copy and paste you have go into edit mode. For older editions, you'll have to resort to other means. If you're too lazy to go get your code book out of the truck, I'd advise not trying to use the NFPA online viewer. Perhaps the following link will help:

https://archive.org/details/gov.law.nfpa.nec.2011
 
Smart $ said:
I don't believe it is possible. If you want to view current edition [2014], you can use the online NEC Public Input... but to copy and paste you have go into edit mode. For older editions, you'll have to resort to other means. If you're too lazy to go get your code book out of the truck, I'd advise not trying to use the NFPA online viewer. Perhaps the following link will help:

https://archive.org/details/gov.law.nfpa.nec.2011
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I have PDFs of the 99 through 2011 with just the code text. The only hand book I have is the 2014...not really sure why I bought it as I don't normally buy the handbook.
 
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