Armored cable installed in thermal insulation shall have conductors rated at 90°C (194°F). The ampacity
of cable installed in these applications shall not exceed that of a 60°C (140°F) rated conductor. The 90°C (194°F) rating shall be permitted to be used for ampacity
adjustment and correction calculations; however, the ampacity
shall not exceed that of a 60°C (140°F) rated conductor.
Where more than two Type AC cables containing two or more current-carrying conductors in each cable are installed in contact with thermal insulation, caulk, or sealing foam without maintaining spacing between cables, the ampacity of each conductor shall be adjusted in accordance with Table 310.15(C)(1).