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.
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?
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.
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; 11/16/1007:47 PM. Reason: Added note
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)."
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)