feeder wire size?

[kcolwell]

I'm studying for an exam and would greatly appreciate some assistance with one particular question.

Here are the details...

is this design adequate for 3200 amp main in building (277/480v)

8 runs of 4" PVC from the utility's transformer to the main in the building routed underground (approximately 40 feet) with sets of 500kcmil in each of the 8 conduits

...I tend to get tripped up on the derating issues...

Is this adequate? Any thoughts would be greatly appreciated. Thanks!

 

[bob]

Go to table 310.16 and look up the rating for 500 kcm. Multiply it by the number of runs. Is it adequate? Come back and tell us your answer.

 

[bdarnell]

You didn't specify copper or aluminum, but either way, the answer is no. Hopefully you have found this in 310.16 as Bob suggested.

 

[james wuebker]

Don't forget you need a GFCI main on this system.
Jim

 

[james wuebker]

I forgot one item, Your luck of finding a 3200 amp main breaker will be hard so if you use a 3000 amp GFCI then you can run 8 sets of 500 MCM to cover this main.
Jim

 

[infinity]

Don't forget you need a GFCI main on this system.
Jim

Don't you mean GFPE?

 

[bob]

You are not supposed to do it for hom James. He needs to learn to make the effort on his own. :lol:

 

[pierre]

This is a question that some have difficulty with. Was there more to the question than the way you posted, such as the load, and/or type of load?

Take a look at Art 230, Part IV Service-Entrance Conductors.
230.42 Minimum Size and Rating.