I also posted this in the engineering section. Not 100% sure where it belonged. Here is the scenario. We are feeding a temp service from a piece of switchgear 340' from the drawn utility pole using a 300amp breaker. We are bringing (3) 500kcmil AL feeders to a 24x24 j box with ilsco distribution blocks. Then tapping the 500's to the two fused disconnects. My coworker is telling me that we need to continue the 500's on the load side of the distribution block to the line side of the two disconnects to carry the full ampacity of the feeders. Then we can change the wire size after the fuse. I read the tap rule differently. As we are less than 10' and carrying more than the 1/10 of the ampacity of the feeder, then we can step the wire down right at the tap to 4/0 for the 200amp, and #1 or #2 for the 100amp. Looking for more opinions on the topic.
