Correct service entrance conductors size ?

[Bill Annett]

I have a person who installed a double gang meter socket with 2 –200 A panels. They said they installed one conduit with 6 - 4/0 AL conductors. I have not seen it yet but I think that the conductors are what we use to call URD. I think that they are USE-2.

Now there are 6 conductors in the conduit, I will have to de-rate them asper Table 310.15 (B) (3) (a). My question is do I use the 90 degree rating or use the 75 degree rating?

My other question is about article 230.42. I looks like the ampacity of the services conductors is determined by a calculated load and not the size of the two service disconnects, does that sound correct?

I hope that this makes sense.

Any information will be very helpful. Thanks, Bill

 

[jumper]

Assuming USE-2, derate with 90C, but final ampacity needs to be at least the 75C ampacity.

Yes,service conductors are sized according to the calculated load, not the size of the 2 disconnects.

 

[Bill Annett]

Jumper,

Thanks for the quick response. I knew that you could do a load calculation for 3 or more services but did not really know about 2 services. Thanks again for the information.


Bill