Question on 501.10 Wiring methods. 1a Exception RNC is allowed if encased in 2" of concrete and covered 24" to grade. The question is, does the RNC require encasement the total length of the RNC run or just in the classified area,i.e. the conduit is only in 15 feet of the classified area and runs several hundred feet outside of the classified area.
Article 501
- Thread starter ramjet49
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- Mission Viejo, CA
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- Professional Electrical Engineer
The RNC must be encased the entire length except where specifically permitted to be ommitted the entire length.
Personally, I believe it is the 24" cover that is suspect. Originally, it came from NFPA 30. When they originally added the 501.10(A)(1)(a) Exception, CMP 14 had documentation that 2" encasement was effective to prevent external propagation. They didn't have direct documentation for the 24" cover, but it was already permissible per NFPA 30 & 30A which is actually controlled by a different NFPA Technical Committee.
Personally, I believe it is the 24" cover that is suspect. Originally, it came from NFPA 30. When they originally added the 501.10(A)(1)(a) Exception, CMP 14 had documentation that 2" encasement was effective to prevent external propagation. They didn't have direct documentation for the 24" cover, but it was already permissible per NFPA 30 & 30A which is actually controlled by a different NFPA Technical Committee.
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