The Canadian Electrical Code and the Cable Bus Systems

Cable Bus Systems are cable duct systems which, however, maintain a distance of at least one diameter between the cables of individual three-phase circuits and between the various circuits.
Canadian rules for cable duct sizing are very penalising if no air separation is maintained between cables.
This leads, especially in Canada, to the use of these systems, which allow the full capacity given in Table 1 of the CE Code to be used, without downgrading for the number of cables in parallel. Of course, Table 5A must always be applied for correction in the case of temperatures above 30°C.