Fuses

[mparkstexas]

Does anyone know where I can find a section in the NEC that talks about sizing the fuses of a 3 phase circuit. i.e. a 90A, 208V, 3 phase fused disconnect, what are each of the 3 individual fuses rated at. Is each on sized for the full 90A? This is what I am assuming, but I would like to put my mind at ease =-)

Thanks in advance.

 

[jumper]

You fuse each phase at 90 amps. 30amps +30amps+30amps does not equal 90 amps in three phase.

 

[somedudeindallas]

Is there a specific section that lays this out?

 

[augie47]

The basic rule I would think would be 240.4 which states conductors shall be protected in accordance with their ampacity.
Other factors (Articles) might give reason to reduce or increase the protection

 

[jumper]

Also to add what Augie said 210.20(B) takes you to 240.4.