4" CONDUIT FILL

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kwired said:
Also I don't think anyone mentioned yet is you would need to adjust ampacity because there is more than three current carrying conductors in same raceway, which ultimately will also mean increase in conductor size is needed.
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It was mentioned in post #8. :) And it sounds like these may be secondary conductors so the next size up rule doesn't apply.
 
Ok, im sorry for the confusion, ill explain the whole system .A 500kva pad mounted xformer 13.8kv-480/277 -- secondary conductors(2 sets of 500 mcm) protected by a 600AT pad mounted enclosed circuit breaker, feeds a switchgear inside a building (via 600amps ATS), main circuit breaker of switchgear is 800 amps. (note emergency side of the ATS is connected from a 300kw Generator via 600a breaker.
 
infinity said:
So the secondary feeds a 600 amp OCPD? Your earlier post mentioned 800 amps. Can you explain the installation from beginning to end including the secondary conductor length?
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Ok, im sorry for the confusion, ill explain the whole system .A 500kva pad mounted xformer 13.8kv-480/277 -- secondary conductors(2 sets of 500 mcm) protected by a 600AT pad mounted enclosed circuit breaker, feeds a switchgear inside a building (via 600amps ATS), main circuit breaker of switchgear is 800 amps. (note emergency side of the ATS is connected from a 300kw Generator via 600a breaker. secondary conductor length is around 30 ft.
 
RLMJR said:
Ok, im sorry for the confusion, ill explain the whole system .A 500kva pad mounted xformer 13.8kv-480/277 -- secondary conductors(2 sets of 500 mcm) protected by a 600AT pad mounted enclosed circuit breaker, feeds a switchgear inside a building (via 600amps ATS), main circuit breaker of switchgear is 800 amps. (note emergency side of the ATS is connected from a 300kw Generator via 600a breaker.
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That's more clear thanks.

Conductor ampacity:
The 600 amp conductors are protected at the transformer and run into the building making them a feeder.
500 kcmil is good for 380 amps: 380*2 sets=760 amps.

Raceway:
Put that in one raceway and you need to derate: 760*80%=608 amps so you're conductors size is good.
The 4" raceway is too small so you would need to use a larger raceway if you're only using one. 5" RMC would work. Using two 3" PVC raceways with 350 kcmil would also work. Each raceway would have 4-350's+1-#1 EGC.

EGC size:
T250.122 for 600 amps EGC size is minimum #1. Two small EGC's cannot be paralleled to make a larger one.
 
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