Demystifying the 2011 NEC Part 2
“While commercial and industrial rooftops are increasingly used as platforms for PV systems, the primary goal of the roofing system is weatherproofing. A representative from the roofing industry offers insights on how to meet your PV power generation goals without compromising functionality, durability and maintainability of the roof. “
BY JIM KIRBY, AIA
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Systems over 600V:
If you come across a need to know if there isa different rule for a system that is over 600V DC, you can look to the NEC Table of Contents. Here you will see the breakdown of areas in the codebook. Chapters are broken into Articles, and Articles are broken into sections in roman numerals. The voltage levels are defined in these roman numerals.
Article 225, III
Article 314, IV
Article 690, IX
We briefly discusses the importance of expansion fittings and knowing how to calculate how many are needed in order to accommodate for thermal expansion in conduit in order to protect conductors. The Index was pointed out as a great navigation tool. Notice if you look up “expansion” in the codebook index you find several references, the second being Article 300.7(B).
Pay special attention to this article. Notice that the informational note references 352.44 (PVC table) and 355.44 (RTRC table) and gives you how to calculate the expansion for other conduits by multiplying the number from the table by either .2 or .4 depending on what type of conduit you are dealing with. When performing these calculations, pay special attention to which table you are using and which conduit you are determining expansion for.
Did you know about the torqueing table? Check out Annex I on page 828 in the Codebook: Recommended Tightening Torque Tables from UL Standard 486 A-B.
Do you know any electrician lingo terms, slang, or otherwise useful vocabulary that might help on the PV Installation Pro. Exam? Share it in the FORUM!
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