Feeder question

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I have this dilema where I have a 225A feeder ( 2 1/2"C, 4 #4/0, 1 #4 GRD) feeding a panelboard. The problem is that a 2" conduit was ran underground when they poured the slab. (The original feeder was smaller, then more equipment was added on this panel so I had to increase the amperage). There is actually two 2" empty conduits but I believe the feeder has to run in the same conduit if I'm not mistaken. The structure is already up and they are just building out the space now so we can't run a new feeder overhead being that the electrical room is not attached to the structure. Appreciate any suggestions on how to rectify this situation. Thanks.
 
You can run parallel feeders in 2 conduits however the minimum size conductor would have to be 1/0. Art.310.4. Can you downsize the neutral and make it work in one 2" conduit?
 
Thanks Dennis. I just read the 310.4 article. So if I'm understanding this correctly, I would need to run (2) 4 #1/0, 1 #1/0 in each of the two empty 2" conduits to feed the 225A panel?
If so, can all those wires fit on the lugs or would I have to change the panel lugs to accomodate the wires?
 
That's correct however you need to look at 250,122(B)& (F) for the equipment grounding conductor

You will probable have to get double lugs for the panel, or put a trough under the panel and enter with 4/0
 
Your 1/0 minimum far paralleling does not apply to your equipment grounding conductors. That can still be a #4 in each conduit.
Termination would depend on the rating of the lugs. If you parallel two conductors, a single lug would need to be rated for two conductors.

(Sorry, Dennis... I waited but obviously not long enough)
 
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