Watch out...there are strict rules about WHERE you can drill in manufactured beams!
For the most part do not get out of dead center.
As for the wires...20 is too many for one hole no mater what the cable is feeding!
310.15(B)(2)(a) 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). (the preceeding was copied from another post on the subject)
[This message has been edited by mustangelectric (edited 12-07-2004).]
Electricity has no respect for ignorance!