# how to size Secondary conductors for OA/FA/FOA, 55/65 C Transformer



## glen1971 (Oct 10, 2012)

jcmillar2000 said:


> Do you size the transformer secondary feeders for the Nameplate max rated KVA. FOA KVA is the max Rated KVA. Thank you for your shared experience.


Where are you located at? Tough to give code references without knowing a bit of info..

There's more to it than just using the ampacity of the transformer.

Are you an electrician?


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## joebanana (Dec 21, 2010)

Basically it's
1) Determine pri. to sec. ratio. ie. 480/120=4
2) Multiply pri. OCPD by 1/3:5 x 1/3=1.67
3) Multiply 4 x 1.6=6.67a.
4) Look in table T 310.16, 60 degree C column for the smallest conductor with an ampacity larger than 6.67a.


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## Bird dog (Oct 27, 2015)

Please fill out your profile. We like to know who we're talking to.


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## emtnut (Mar 1, 2015)

jcmillar2000 said:


> Do you size the transformer secondary feeders for the Nameplate max rated KVA. FOA KVA is the max Rated KVA. Thank you for your shared experience.


nope


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