Sizing Transformer Grounds

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alsw

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112.5 KVA 480 DELTA to 208WYE XO TO BUILDING STEEL .WHAT SIZE CONDUCTOR.
75KVA 480 DELTA to 480 WYE XO to BUILDING STEEL.NEEDS WHAT SIZE CONDUCTOR.
 
See 250.30(A)(3) and please turn off your Caps lock, it's considered yelling.

Roger
 
You need to provide us with the size of the secondary conductors to answer the question.
 
Assuming that your secondaries have copper conductors:

#3/0=167,800 circular mils
167,800(2)=335,600 circular mils (335.6 kcmil)

Table 250.66

Over 3/0 through 350 kcmil= #2 copper

Both transformers would require a #2 copper GEC.
 
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