Derate by 1% to 2% per 300 meters above 2,000m.
12 current-carrying conductors in bundle: $K_group = 0.50$ (NEC 10-20 conductors)
Running a 90°C XLPE cable through a 70°C boiler room reduces its capacity by 42%. A 100A cable becomes a 58A cable. 2. Grouping / Bundling Derating ($K_group$) The Physics: When cables are tied together in a tray, conduit, or bundle, they heat each other. The inner cables cannot radiate heat outward.
