transformer

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Electric-D

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can someone tell me where to find in the nec. where or how to the find wire size for a any transformer on the primary side is there a table, chart, what?
 
you won't find such a chart in NEC. Too many varibles. 450.3 will help you decide the maximum overcurrent to provide transformer protection.
From that you can select your overcureent and wire size.
however, normally you take the step of determining load, transformer size, and select overcurrent & wire size from that keeping Art 450 and Art 240 in mind.
 
transformer

i have a 500A load on the secondary side, in which i'm going to paralell (2) 200A sub panels w/a 75kva transformer 480/208y/120 single phase. is there any division or multiplication involved in the formula?
 
darren patton said:
i have a 500A load on the secondary side, in which i'm going to paralell (2) 200A sub panels w/a 75kva transformer 480/208y/120 single phase. is there any division or multiplication involved in the formula?
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Yes there is division and multiplication involved in the formula and if you are a licensed electrician you should know how to make the calculation.
From this information, the equipment you show is not adequate for a 500 amp load. Suggest you get a licensed electrical contractor to help you.
 
Originally Posted by darren patton
i have a 500A load on the secondary side, in which i'm going to paralell (2) 200A sub panels w/a 75kva transformer 480/208y/120 single phase. is there any division or multiplication involved in the formula?

If u have a 75kva transformer your max load on the secondary side would be

75000/208/1.732= 208.19amps
 
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