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#197143 11/11/10 02:56 PM
Joined: Nov 2007
Posts: 763
K
KJay Offline OP
Member
Looking over the changes to what was previously Table 310.16, does this mean we can no longer use 20A for #14 and 25A for #12 at 60-degree C for derating purposes?
If so, I can see this causing some new installation issues requiring conductor upsizing.

2017 / 2014 NEC & Related Books and Study Guides
KJay #197182 11/13/10 07:51 PM
Joined: Nov 2007
Posts: 763
K
KJay Offline OP
Member
Hmmm, no input on this?

KJay #197193 11/14/10 01:39 PM
Joined: Jul 2004
Posts: 9,672
Likes: 7
G
Member
I don't have the 2011 yet. I suppose that may be why other are not jumping in.
Did they change the 60c rating for small conductors?
I can see this affecting motors and HVAC more than derating.
Don't you derate from the 90c?


Greg Fretwell
Joined: Nov 2007
Posts: 763
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KJay Offline OP
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Good point. I donít have my new code book in hand yet either, so I guess Iím getting a little bit anxious since around here we have to be ready to hit the ground running on January 1.

KJay #197249 11/16/10 02:08 PM
Joined: Jul 2004
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G
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Florida won't get around to adopting this until 2012 or later if the past is any indication.

I am really waiting for the handbook CD. I don't travel around much and I am starting to like the CD format.
I will probably just buy it here at ECN. Last time they were about the same as everywhere else and I would just as soon help out these guys.


Greg Fretwell
Joined: Apr 2002
Posts: 7,283
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Greg:
I have a 2011 & the 'free' PDF. When I get home tonite, I'll try to cut/paste 310.16 & get it up here.

I have NOT had any time (to speak of) to open the 2011 yet, & like you, I'm waiting for the handbook & CD.



John
Joined: Apr 2002
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Here's part of 310.15(b)
"(B) Tables. Ampacities for conductors rated 0 to 2000 volts
shall be as specified in the Allowable Ampacity Table
310.15(B)(16) through Table 310.15(B)(19), and Ampacity
Table 310.15(B)(20) and Table 310.15(B)(21) as modified by
310.15(B)(1) through (B)(7).
The temperature correction and adjustment factors shall
be permitted to be applied to the ampacity for the temperature
rating of the conductor, if the corrected and adjusted
ampacity does not exceed the ampacity for the temperature
rating of the termination in accordance with the provisions
of 110.14(C).
Informational Note: Table 310.15(B)(16) through Table
310.15(B)(19) are application tables for use in determining
conductor sizes on loads calculated in accordance with Article
220. Allowable ampacities result from consideration of
one or more of the following:
(1) Temperature compatibility with connected equipment,
especially the connection points.
(2) Coordination with circuit and system overcurrent protection.
(3) Compliance with the requirements of product listings
or certifications. See 110.3(B).
(4) Preservation of the safety benefits of established industry
practices and standardized procedures.
(1) General. For explanation of type letters used in tables"

Anyone who can enlarge this font, please do so (with my blessings)

Last edited by HotLine1; 11/16/10 07:47 PM. Reason: Added note

John
Joined: Nov 2007
Posts: 763
K
KJay Offline OP
Member
Regarding the article HotLine posted above, does this mean we can still us the 90C column for derating purposes for NM cables or must we now start at 60C.

"The temperature correction and adjustment factors shall
be permitted to be applied to the ampacity for the temperature
rating of the conductor, if the corrected and adjusted
ampacity does not exceed the ampacity for the temperature
rating of the termination in accordance with the provisions
of 110.14(C)."

KJay #197301 11/18/10 04:56 PM
Joined: Apr 2002
Posts: 7,283
Likes: 3
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Not to be critical, but....that sounds like one of our (NJ) many lawyers wrote that!

I'm pondering what it says when time permits


John
Joined: Jul 2004
Posts: 9,672
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G
Member
I don't read this as changing anything. We have always limited the ultimate ampacity to the rating of the termination.
You just use the 90c column for dealing with ambient temperature and bundled conductor adjustments.
If you are using one of the restricted cables (AC, MC, RX), you end up with the 60c limit anyway.

They did change the name of 310.16 to 310.15(B)(15) but I don't think it changed. (that was a Mike Holt proposal, just to maintain continuity in 310.15)


Greg Fretwell
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