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  1. JGoldberg

    Embedded Concrete RHO

    I'm trying to calculate power cable sizing for an underground ductbank in which the RHO of the soil is known to be 120. The ductbank is currently being designed hence, the RHO of the concrete in unknown. NEC Annex B.310.15(B)(2) states that concrete = 55 RHO typically. It also says soil RHO =...
  2. JGoldberg

    Derate cables - solar pickup

    When running power cables outdoors exposed to the sun, is there an additional ampacity derating factor due to solar energy pickup? The NEC only addresses ambient temperature considerations for ampacity derating, not the extra energy absorbed by the cable due to solar energy radiation.
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