Code Change Summary: The title to table 310.15(B)(3)(a) has been modified. And the note under the table now makes it clear that the table also applies to spare conductors.

Table 310.15(B)(3)(a) provides adjustment factors when installing more than three current-carrying conductors (CCC). Previously, the table only applied when there were more than three CCC “in a raceway or cable”. Now it is clear that the adjustment factors in the table are not just required when a raceway or cable contains more than three CCC.

A good example of this is when separate cables are installed without maintaining spacing. For these installations, if cables are bundled for a continuous length longer than 24 in., the allowable ampacity of each conductor must be reduced as shown in Table 310.15(B)(3)(a).

Two more changes occurred in the note under the table:

• The table now applies to spare conductors. Often, spare conductors will eventually turn into current carrying conductors in the future.

• The table does not apply to conductors that cannot be energized simultaneously. For example; There is no need to consider two travelers to a 3-way switch as two current carrying conductors since only one of the two can be energized at any given time.

See image for an example of Table 310.15(B)(3)(a).