Looking at the Regs, particularly Table 4C3, it would appear that only one multicore cable is allowed in a buried duct (i.e. "single way duct"). The 'Rating Factor' seems to be applied to the number of ducts, not the number of cables.
I've seen numerous installations where more than one cable is installed in a single duct - is this acceptable and, if so, how is the grouping factor applied?
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