Sizing System Bonding jumper in Transformer

[shawnbebout]

Hey, guys, need some help in an argument and I have to get to my kids soccer game.
Where does it specify how to size the system bonding jumper? Bonding the XO to the frame of a transformer. I told the guy my answer (based on 250.66), but where does it reference me to that?
Thanks

 

[Dennis Alwon]

Depending what year code book you use 250.66 is correct. In the 2014 the table was added for bonding -- T. 250 102(C)(1) which is virtually the same as T 250.66

(D) Size. Main bonding jumpers and system bonding
jumpers shall be sized in accordance with 250.28(D)(1)
through (D)(3).
(1) General. Main bonding jumpers and system bonding
jumpers shall not be smaller than the sizes shown in
Table 250.66. Where the supply conductors are larger
than 1100 kcmil copper or 1750 kcmil aluminum, the
bonding jumper shall have an area that is not less than
121?2 percent of the area of the largest phase conductor
except that, where the phase conductors and the bonding
jumper are of different materials (copper or aluminum),
the minimum size of the bonding jumper shall be based
on the assumed use of phase conductors of the same
material as the bonding jumper and with an ampacity
equivalent to that of the installed phase conductors.