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#91852 02/09/05 12:20 PM
Joined: Mar 2003
Posts: 849
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Table 310.73 2001-5000 volts M.V.105.
500kcmil =530 amps for derateing 475 for terms(110.40). As i see it no derateing for a bank of pipes in open air. Thus 2000 amp requirement = 4 sets 530x4=2120
or 4 sets 475= 1900 amps.
240.101 states fuse can be 3 times conductors ampacity breaker or electronically actuated fuse up to 6 times.


So as I see it conductors must be rated for the ampacity of the true load. Over current protection can be higher then conductor rateings.
The highter amps rateing 105% for derateing only the 90% rateing for terms.
so if load is 1900 amps or below 500s can be used ,fused at 2000 amps.

2017 / 2014 NEC & Related Books and Study Guides
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Bob Offline
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Yoopersup
What is the load your are working with?

Joined: Mar 2003
Posts: 849
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Last sentence says 1900 amps or below.


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