Transformer GEC vs EGC 250.122, 250.66

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Npstewart

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I received a building department comment that exactly reads:

It appears that an equipment grounding conductor from the transformer to panel ?K1? is sized per 250.122. The transformers are separately derived AC systems and the transformers have a grounding electrode system installed per NEC 250.66 & 250.30.

Situation:
I have a 112.5 kva transformer feeding a 400A MCB panel. I am using a parallel feeder of (4) #3/0 and (1) #3 EGC to feed my 208/3 panel from the transformer. I have a detail that shows a ground bus in the transformer, the ground bus has a GEC sized per 250.66 ( I used a 2/0) and coming out of the ground bus I have a EGC which is the #3 which goes to feed my panel. My detail also shows bonding jumper etc etc.

I think he wants me to run a 2/0 GEC to the panel if I am reading him correctly, am I missing something here? Is this correct??
 
I don't quite understand if your parallel sets are in one conduit or two.

If you have two conduits, you would need a supply side bonding jumper in each. It would have to be #4 minimum per 250.66.

If the parallel sets are in one conduit, the supply side bonding jumper would need to be #2 minimum per 250.66.

250.122 does not come into play between the transformer and the panel.
 
As mentioned your SSBJ's need to be sized according to the phase conductors in each parallel raceway according to table 250.66 which is #3 Cu.

Your system bonding jumper and GEC are sized according to the parallel sets by the equivalent size of a single conductor in Table 250.66.

#3/0=167800 circular mils
#3/0 * 2 sets = 335600 circular mils

Table 250.66 over #3/0 to 350kcmil = #2 Cu GEC and system bonding jumper
 
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