5KVA Transformer 480-208/120V breaker sizing

[Cartoon1]

Hello. I have a long distance run to a equipment (exterior) that needs a 240V for input single phase. I'm running a 480V from the panel to a small 6KVA stepdown transformer near the equipment. This equipment draws 15Amps single phase at 240V. My understanding is the closest transformer to handle the load is a 5KVA transformer. I'm placing the transformer near the equipment after the long 480V run about (300Feet).

Per Table 450.3(B):
Primary: 5KVA / 480V = 13A * 1.25 = 13.02A. The closest breaker is a 15A breaker at the 480V panel.
Secondary: 5KVA / 240V = 20.8A * 1.25 = 26.04A. I'm putting secondary disconnect switch rated (30A) with 25A fuse.

Is my calculations okay? would it be better/permissible to change the breaker to 20A for primary? And do small transformers come with an integrated overload device?

Thank you,

 

[Strathead]

Per table 450.3 the primary is allowed to be 250% so 13A * 2.5 = 32.5A. Since I don't see the "next larger breaker size" for this I would say you need to use a 30A maximum breaker on the primary.

 

[augie47]

You mentioned 6 kva.... That is normally a 3 phase transformer
Are we looking at 3 phase or single phase ??

 

[tom baker]

I suggest you use a Sq D Mini Power Zone. It’s an all in one primary disconnect, 5 Kva transformer and secondary panel, it’s NEMA 3R rated. Set a post, drive 2 ground rods and you are done. I have used at golf courses and for scoreboards. Other manufactures may have a similar product.

 

[Cartoon1]

You mentioned 6 kva.... That is normally a 3 phase transformer
Are we looking at 3 phase or single phase ??

Sorry my mistake. It is a 5KVA single phase.

 

[Cartoon1]

I suggest you use a Sq D Mini Power Zone. It’s an all in one primary disconnect, 5 Kva transformer and secondary panel, it’s NEMA 3R rated. Set a post, drive 2 ground rods and you are done. I have used at golf courses and for scoreboards. Other manufactures may have a similar product.

I need to look into that, it will make my life easier. Does it come with a primary and secondary breaker? Or just a disconnect switch?
Thank you,

 

[jim dungar]

I need to look into that, it will make my life easier. Does it come with a primary and secondary breaker? Or just a disconnect switch?
Thank you,

It has a both a primary and secondary breaker.