I think not. It sounds like the design is calling for a tap on the switchgear buswork. If there is no overcurrent device upstream of that point (i.e., a main between the transformer secondary and the two feeder breakers), then 240.21(B) does not apply. You would be tapping the transformer secondary, and the rules in 240.21(C) come into play. If the distance were under 10 feet, I think you could use (C)(2). Otherwise, try (C)(6).
Originally Posted by dwinchel
Charles E. Beck, P.E., Seattle
Comments based on 2014 NEC unless otherwise noted.