Wire size for 208V Primary to 480v sec y transformer 112.5kva

[petroc]

Was looking for a little help on wire size and primary breaker size for 112.5KVA transformer 208v primary 480V Y sec also grounding size

 

[augie47]

The conductor size is dependent on the over current device protecting it.
Look at you transformer currents and protect the transformer per 450.3
If you elect to go the 125% primary current rule then your 112.5 kva transformer would require a 400 amp breaker and you would size the conductor accordingly.
With properly sized secondary protection you could use a larger primary breaker and if you choose that route you would still size the conductor based on the over-current device.

 

[texie]

In addition to the conductor size question, just so we are clear, is this a step up application with a 208 volt delta primary and a 480Y secondary?

 

[petroc]

In addition to the conductor size question, just so we are clear, is this a step up application with a 208 volt delta primary and a 480Y secondary?

Yes the main panel has 400A and need to hook this up for Granite saw application.about a 20ft run to shop.
Transformer provided to my customer from the saw manufacturer is a 112.5 KVA 208V PRIMARY 480V y/277 secondary

 

[augie47]

If the panel already has a 400 amp I would check the lugs to see if they accept two conductors and if so I would likely run parallel 3/0s, if not, a 500 kcmil.
Don't forget with a 480/277 secondary you will need to establish a grounding electrode system.