Adding to a 800 amp service

[electricblue]

I have an 800 amp service and need to add 200 amps. Do all feeders have to add up to the main amperages or are there some derating factors? I've seen a 1200amp service with 8 200 amp feeders thus adding up to 1600amps.

 

[Cow]

This is no different than a loadcenter in a home where the breakers more often than not, add up to more than the main.

You must do a load calc per art. 220 to determine if your 800 amp service can serve the additional load you're adding.

 

[iwire]

You must do a load calc per art. 220 to determine if your 800 amp service can serve the additional load you're adding.

That is the bottom line, you either do the load calculation or you are guessing.

Sometimes the guess can be pretty good but they do not have a section in article 220 for best guess.

 

[kwired]

That is the bottom line, you either do the load calculation or you are guessing.

Sometimes the guess can be pretty good but they do not have a section in article 220 for best guess.

220.152(A)(3)(b)(2) gives pretty good detail on how to guess.

 

[electricblue]

Awesome! Thanks