If you are talking like bundling NM cables together…many people in the past would simply run them all together and then tie wrap them…but it can no longer be done that way…because the code now addresses bundling issues.
**(2) Adjustment Factors.
**(a) More Than Three Current-Carrying Conductors in
a Raceway or Cable. Where the number of current-carrying
conductors in a raceway or cable exceeds three, or where
single conductors or multiconductor cables are stacked or
bundled longer than 600 mm (24 in.) without maintaining
spacing and are not installed in raceways, the allowable
ampacity of each conductor shall be reduced as shown in
Table 310.15(B)(2)(a). Each current-carrying conductor of
a paralleled set of conductors shall be counted as a currentcarrying
FPN No. 1: See Annex B, Table B.310.11, for adjustment
factors for more than three current-carrying conductors in a
raceway or cable with load diversity.
FPN No. 2: See 366.23(A) for correction factors for conductors
in sheet metal auxiliary gutters and 376.22 for correction
factors for conductors in metal wireways.
*Exception No. 1: Where conductors of different systems,
as provided in 300.3, are installed in a common raceway or
cable, the derating factors shown in Table 310.15(B)(2)(a)
shall apply only to the number of power and lighting conductors
(Articles 210, 215, 220, and 230).
Exception No. 2: For conductors installed in cable trays,
the provisions of 392.11 shall apply.
Exception No. 3: Derating factors shall not apply to conductors
in nipples having a length not exceeding 600 mm
Exception No. 4: Derating factors shall not apply to underground
conductors entering or leaving an outdoor
trench if those conductors have physical protection in the
form of rigid metal conduit, intermediate metal conduit, or
rigid nonmetallic conduit having a length not exceeding
3.05 m (10 ft) and if the number of conductors does not
Exception No. 5: Adjustment factors shall not apply to
Type AC cable or to Type MC cable without an overall
outer jacket under the following conditions:
(1) Each cable has not more than three current-carrying
(2) The conductors are 12 AWG copper.
(3) Not more than 20 current-carrying conductors are
bundled, stacked, or supported on “bridle rings.”
A 60 percent adjustment factor shall be applied where the
current-carrying conductors in these cables that are
stacked or bundled longer than 600 mm (24 in.) without
maintaining spacing exceeds 20.