600 amp service

[John@Matros]

Afternoon all, I have to design a 600A 3 phase service with limited room. I am using a 800A trans S combo fused down to 600 and will be placing the MDP in another room aprox 25' away. Because of space limitations due to duct work I'd like to run 1 -4" conduit with 2 sets of 350MCM from the load side of the service switch. Does anyone see an issue with running 2 sets in 1 conduit?

 

[dkidd]

Derating

 

[John@Matros]

right so other then that with proper wire size to have 2 sets in 1 properly sized conduit is ok?

 

[charlie b]

With proper size and proper size, the basic notion of two sets of conductors in the same conduit is acceptable. But you are looking at a tight squeze. Two sets of 350 MCM that are rated at 90C will only give you an ampacity of 560. Unless you can show by calculation that the total load is less than that value, you have to use a larger wire. Two sets of 400 MCM will give you enough ampacity for a full 600 amp service. However, depending on the conduit type, getting six phase conductors, two neutral conductors, and one EGC into a 4 inch conduit might not be possible. Also, if the loads are non-linear, so that you have to count the neutrals as current-carrying conductors in the context of table 310.15(B)(2)(a), then you are looking at 500 MCM conductors and a 5 inch conduit.

 

[infinity]

You can fit 9-400 kcmil conductors in a 3.5" EMT or 11 in a 4" EMT. If you run one 4" EMT you can pretty much pull in whatever you need, even 9-500 kcmil conductors.