Transformer calculation Help

[don_resqcapt19]

I do not have one. My error.

The code clearly states that rounding up, from 125%, is allowed. However I see no allowance to round up past 250% (or even past 167%).

I agree..only the two 125% values can be rounded up to the next standard size.

 

[Cow]

Am I understanding this right? Since he has his primary protection sized to the 125% rule(for primary only protection) the oversized secondary OCPD really makes no difference? Had he gone past the 125% rule of primary only protection and went up to 250% for primary protection with secondary protection also then he's noncompliant? That seems to be how I'm seeing it.

It sounds like they installed a 400 amp breaker for no reason?

 

[jim dungar]

Am I understanding this right? Since he has his primary protection sized to the 125% rule(for primary only protection) the oversized secondary OCPD really makes no difference? Had he gone past the 125% rule of primary only protection and went up to 250% for primary protection with secondary protection also then he's noncompliant? That seems to be how I'm seeing it.

It sounds like they installed a 400 amp breaker for no reason?

Yes, you are understanding this.
Except the 400A breaker is protecting the secondary conductors

 

[Smart $]

...Except the 400A breaker is protecting the secondary conductors

Hmmm... I believe that depends just a tad bit :wink: on secondary conductor ampacity, which we do not know at this point.

I notice you tend to differentiate between secondary ocp and secondary conductor ocp. That makes it seem as though one can provide secondary ocp without using secondary tap conductors on say your typical run-o'-the-mill dry-type transformer... :grin: