Can someone please provide a code reference for when it is required to have secondary
protection on a transformer (less than 600VAC and greater than 9 Amps)?
I am interested in utilizing FPN #2 & #3 of NEC Table 450.3 (B), but am unclear
on the intent of the phrase in FPN #2 that states: "Where...
Thank you for the comments dpc. I am also thinking that the intent of the code would
pertain to a situation where the secondary of a transformer is tapped to feed 2 ea.
Main Lug 225 Amp Rated Load Centers, then the wire would need to be sized per the full
"rating" of the device (ie. 225 Amps)...
I agree with your comments, and this is how I would approach
conductor sizing for these applications. But I did not design it
and I was hoping to site the NEC for a clear definition on this.
The calculated load is less than 180 Amps, the MCCB is correctly
sized at 225 Amps, the unprotected...
Thank you for the NEC reference.
Based upon condition of acceptability 240.21 (C)(2)(1),
I am still confused by the requirement for the secdondary
conductor ampacity to be not less than the combined calculated
loads AND not less than the rating of the device supplied by the
secondary conductors...
I am working on a Power Distribution Unit where the ETL Listed Equipment has a 500A Main CB feeding
a 300kVA Delta-Wye Transformer (480: 208/120). The Transformer Secondary Feeds Six 225 Amp Molded Case
Circuit Breakers (ie. Primary Protection Only). What NEC Sections would pertain to the...
