Transformer 2ndary overcurrent protection

[necnec]

First the setting then the question:
480:120, 15KVA (125A), 1-phase xfmr...
Industrial installation...
2ndry leads are less than 25 ft long...
Both primary leads protected...
2ndry leads (2AWG) go to a power distribution block (PDB) which fans out with (8) #14 wires each to their own breaker...
PDB and all breakers are in the same enclosure...

Question: does the xfmr 2ndry need a 125A overcurrent protection?

Thanks!

 

[don_resqcapt19]

Re: Transformer 2ndary overcurrent protection

If this is a 2 wire to 2 wire transformer, the primary OCPD is permitted to protect the secondary conductors if the installation meets the requirements of 240.21(C)(1). If the maximum permitted OCPD per 450.3 is used for the primary, then the secondary conductors would have to have an ampacity of 160 amps to be considered protected by the primary OCPD.
You can't apply 240.21(C)(3) for the protection of the #2 secondary conductors because the eight 15 breakers have a total rating of 120 amps. This section requires that the sum of the OCPDs do not exceed the conductor ampacity. The ampacity of #2 is only 115 amps. 240.4(B) does not change the ampacity of a conductor, it just permits, in some cases, an oversized OCPD.
I also question if it is permitted to connect the #14s to the #2s without an OCPD. This appears to be tapping a tap, which is prohibited by 240.21.
Don