How is Article 310.15.(B)(2)(c) applied in your area? What is used for a base temperature? Can one use the information on the weather channel for your area's average temperature on the hottest month of the year? Do you have to use the ASHRAE Handbook? How about that 3 questions for the price of one
Thanks Greg, since I live in a northern state, we don't have much of an issue with this type of installation but I'm sure you might or possibly some other state.
I got this back From Bryan Holland (BHGravity here)
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I am using the guidelines established by the CDA. As indicated in the FPN, the CDA guidelines utilize the average of the 2% ASHRAE design temperatures for each region and major city in the state.
The guildelines and sliding scale card can be obtained FREE from www.copper.org _________________________ Bryan P. Holland, ICC Electrical Code Official CBO, Plans Examiner, Inspector, Instructor Secretary - IAEI Florida Gulf Coast Division Secretary - BOAF Gulf Coast Chapter
In Las Vegas the local ordinances super-cede this Code provision.
Ground temperatures are considered such a threat that the typical PVC-under-slab run is restricted to absolute minimums and the conductors get derated.
Hence, a grocery store ( example ) has all of its circuits run in EMT overhead and de-rated one bump.