I recently ran across a situation and need some help. I recently found a panel (3 phase 4 wire 277/480volt) that has a 70 amp 3 pole breaker that feeds numerous pull boxes in a building. Each pull box is approximately 100 feet from the next one. The wire feeding the pull boxes is #4 awg throughout. At each pull box, the previous installer has tapped into one leg of the (i'm assuming they alternate legs)feeder with a #10 that is then run approximately 30 feet to a 30 amp 3 phase disconnect and the single leg is fused with a 30 amp fuse. The load side runs to the fan coil which is rated at 30 amps.
My question: I think the breaker can only 30 amps due to the #10 tap that is run from the pull box to the disconnect. Is this correct?
If it can only be 30 amps, what would be the least expensive way to correct the problem. Can a fused disconnect be mounted at the pole box and fused at 30 amps?
Can you give me a specific code I can reference?
Thanks for you help
My question: I think the breaker can only 30 amps due to the #10 tap that is run from the pull box to the disconnect. Is this correct?
If it can only be 30 amps, what would be the least expensive way to correct the problem. Can a fused disconnect be mounted at the pole box and fused at 30 amps?
Can you give me a specific code I can reference?
Thanks for you help