Transformers feeder conductor size

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xformer

Senior Member
Location
Dallas, Tx
Occupation
Master Electrician
When applying table 450.3 to transformers, are the feeder conductors sized based off the OCPD or are they sized based off of the rated ampacity of the transformer?
 

xformer

Senior Member
Location
Dallas, Tx
Occupation
Master Electrician
Ok... So, If I have a 45KVA 480V / 208V transformer installation with primary and secondary protection as in Table 450.3(B), When I Size the Primary at 250% of the primary Current, the feeder conductors have to be sized to the OCPD for the feeder?
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
afraid so.
that's one reason it's a bit uncommon to find 250% primary protection on a single transformer.
 
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