Buss Plug Sizing

[d21x]

I have a 480V 3 Phase 45kVA transformer that I am installing. That's equivalent to ~55 amps. Is it okay for me to use a 60 Amp Buss Plug and 60 Amp Safety Switch? Or should I step it up to a 100 Amp?

 

[iwire]

Either could be code compliant depending on the load your plaining on the load side of the transformer.

If you are planing on being able to running the transformer at 45 KW continuous a 60 on the primary is too small, you would need at least a 70 amp fuse on the primary.

 

[fjrivera]

I agree with iwire that the 60A overcurrent protection on the primary is too small depending on the load but is code compliant. You could check NEC 450.3 and table 450.3(B) and a maximum 70A primary only overcurrent protection can be used giving you more flexibility.