Tap Rule

[Big Guns]

If you have 480 volt 3 phase transformer feeding a 208 volt 3 phase main lug panel, do you need a disconect on the secondary side if panel is more than 10 feet away from transformer, but closer then 25 feet.

 

[augie47]

I read that wrong at first..thought we had 480 feeding a 208 panel
A transformer with a 208Y120 secondary must have overcurrent protection on the secondary side {240.21(C)(1)}
If the primary is protected per 450.3 @ 125%, the secondary protection
can be sized to match the conductors and panel. In your case (>10, <25 ft) 240.21(C)(3), (4) or (6)

 

[pete m.]

What Gus said.... plus you may want to check 408.36 (2008 NEC)

Pete

 

[don_resqcapt19]

...
A transformer with a 208Y120 secondary must have overcurrent protection on the secondary side {240.21(C)(1)}

Actually the secondary of the transformer does not require protection. It is the secondary conductors that require protection. The rules in Article 450 cover the required primary and secondary protection of the transformer. The rules in Article 240 cover the required protection of the secondary conductors.

 

[augie47]

I stand corrected... often my statements need interrupters

 

[chris kennedy]

often my statements need interrupters

Get married.

 

[augie47]

Get married.

I did.... those statements are mummered..