800 service feeder sise

[Toros]

Hi ,I have a 800A, 3-phase, 4-w, 120/208V service (No main Brker) with total demand load of 600A. Should I use (2)2" EMT & (4)#350 MCM in each or, (2)3" EMT & (4)#500 MCM in each or, (2)3" EMT & (4) # 600 MCM. Should I consider the rating of bus which is 800A or demand load which is 600A Also, I am using NEC , table 310-16; should I use column 75 deg. or 90 deg. (Temperature dating, because it is outdoor )

 

[Smart $]

Hi ,I have a 800A, 3-phase, 4-w, 120/208V service (No main Brker) with total demand load of 600A. Should I use (2)2" EMT & (4)#350 MCM in each or, (2)3" EMT & (4)#500 MCM in each or, (2)3" EMT & (4) # 600 MCM. Should I consider the rating of bus which is 800A or demand load which is 600A Also, I am using NEC , table 310-16; should I use column 75 deg. or 90 deg. (Temperature dating, because it is outdoor )

Assuming "No main Brker" means multiple service disconnect switches connected to one 800A bus, you only need to size the service conductors for the calculated load + 25% for the continuous load portion thereof.

You use the column matching the conductor type for ampacity derating.

In simple terms, the least of the derated conductor ampacity value, the value for the conductor size in the column which your equipment is rated [110.14(C) termination temperature limitation], and the OCPD rating value (does not apply to multiple service disconnecting means), must equal or exceed the calculated load + 25% for the continuous load portion thereof.