3000 amp service

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cvirgil467

Senior Member
Location
NewYork
ok, no load is know about a building but the owner says he needs a 3000 amp service. How would you size the condcutors using 500kcm?

option 1 - using 75 deg c - take 80% of 380 = 304 amps.

3000 amps / 304 amps = 9.8 sets = 10 sets of 500 kcm

option 2 - using 90 deg c - take 80% of 430 = 344 amps

3000 amps / 344 = 8.7 sets = 9 sets of 500kcm

Option 3 - using 75 deg c - using 100% ampacity of conductor - 380 amps

3000 amps / 380 = 7.8 sets = 8 sets of 500kcm
 

teco

Senior Member
Location
Mass north shore
Recently have done a couple of 3000s. Definitely 8 sets of 500 kcmil. Just wondering why you might consider option 1 or 2. More wire, more pipes, more labor?
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Thanks. if 90 deg c conductors used with 75 deg c equipment, could i use the 90 deg ampacity to decrease the # of sets?
You can use 90 deg conductors for derating but you cannot use an ampacity that would be over the 75C rating of the equipment, etc. So the final ampacity will never be higher than the weakest link, in your case it is at 75C.
 
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