So I am looking at a standard duct bank design with 6 conduits that are concrete encased. It is a low voltage duct bank. Some 480V lines, 120V control lines, lighting, heating, receptacles, etc. I may need to place it greater than 30" below the surface. I know for MV this would trigger derating. However, for Low voltage that is not such a rigid requirement. Just wanted to see how seriously out there take this for low voltage.
Low Voltage Concrete Duct bank de-rating.
- Thread starter W@ttson
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For the same reason you might derate MV ductbanks you would do the same for LV. In reality, LV ductbanks are effected by burial more than MV.
Check NEC Annex B
Check NEC Annex B
PD1972
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In practice, the importance of derating for a LV duct bank probably depends on load factor of your loads as well as the type of building. If sizing per article 220 of the NEC for a typical commercial building, the low load factor and demand relative to the ampacity of your installed conductors are usually enough to cover for the derating that occurs in the duct bank. You will most likely never run into an issue of overheating.
However, if this is a duct bank that serves an industrial building that is consistently operating at its peak demand, I would say that it is important to derate using Neher-McGrath.
However, if this is a duct bank that serves an industrial building that is consistently operating at its peak demand, I would say that it is important to derate using Neher-McGrath.
its for an industrial facility and is the feed from a generator placed remotely from the main building. Going to be fun.
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