240.21 (B)(1) (4) For FIELD installations where the Tap conductors Leave the Encloser in which the tap is made The rateing of the overcurrent device on the LINE side of the Tap conductors shall not EXCEED 10 times the Ampacity of the tap conductors. Under this you can make a 100 amp (10 ft conductor tap) off a 1000 amp protected gear. The handout we Received on 6/19/08 Prog. # 14193 at the Michigan IAEI meeting covers this quite well. Also see 240.90 For (Supervised Industral Installations) If the area falls under that.
Ernie- Read the original post again- I read it to be a transformer secondary tap and the code reference you referenced to 240.21(B)(1)(4) is a tap to a feeder. Maybe I'm wrong.
The post doesn't indicate whether or not it is a Supervised Installation.
