3/0 on a 225 amp breaker

[-=PEAKABOO=-]

I should know this answer but something keeps telling me that it is acceptable.
Commercial building 225 main breakers feeding sub panels inside building.
Wire is thhn. Calculated load is well under 200 amps.
Is this acceptable??

Thanks

 

[infinity]

I would say no. #3/0 Cu THHN has an ampacity of 200 amps which is a standard size OCPD ampacity. You need either #4/0 Cu or a 200 amp OCPD.

 

[-=PEAKABOO=-]

Well then I guess it will be four 4/0's and a #4 in a 2"

 

[kbsparky]

What load(s) are you feeding with this? Got a bunch of motors on the other end of that feeder?

 

[chevyx92]

Well then I guess it will be four 4/0's and a #4 in a 2"

That would be a violation. You would need a 2 1/2" conduit.

 

[don_resqcapt19]

That would be a violation. You would need a 2 1/2" conduit.

Not if he uses a bare EGC. There will be 0.0052 square inches left to get to 40% using four 4/0 THHNs and a bare #4 in 2" EMT.
Don

 

[chevyx92]

Not if he uses a bare EGC. There will be 0.0052 square inches left to get to 40% using four 4/0 THHNs and a bare #4 in 2" EMT.
Don

Maybe so but I wouldn't do it. I never use bare wire, it's not on the van and I don't buy it.

 

[-=PEAKABOO=-]

2" is already there.
The panel is not loaded, one has mostly AC units, the other feeds a 112 KVA transformer that is not loaded.
These panels are 277/480 Volt.

 

[winnie]

277V or 480V AC units?

Delta connected transformer?

Why the full size neutral?

-Jon

 

[-=PEAKABOO=-]

Good idea, only three phase loads. The AC's are 480.
One panel is mostly AC's. No single pole breakers, no lights.
The other panel is feeding a Transformer that feeds 120/208 panels that does have lights fed out of it.