Control transformer

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Island sparky

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I'm installing a 480V-120V control transformer to supply a relay with shunt trip voltage. Where do I tap for my 480V primary on this 50VA x-former? Maybe "tap" is not the best way of stating that. How should I supply voltage to this transformer in this I-line panel?
 
I would not think there would be a specific location as long as 450.3, 240.21 and 110.3(B) (as far as "tap" method) are followed.
Is the shunt trip breaker a "main" for this panel ?
 
The way I read 450.3(B) it appears you will have to add fuse protection for a transformer that small (I see no provision for "next larger size"). (The exact fuse size may depend on Note 3).
Depending on how much reliability you want, you could add a breaker or feed the fuses off an existing breaker using the 240.21(B)(1) tap rule.
 
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