transformer question

[Ed Carr]

I am installing some transformers in a building that will be supplying
power to panels in separate buildings. Do I have to protect the secondarys
before they leave the transformer building? The transformers are two each
50kva & 75kva 480 primary 120/240 secondary. Thanks, Ed.

 

[jim dungar]

The secondary conductors must be protected per one of the 'tap rules' in 240.21(C).

 

[KevinVost]

Table 450.3 (B) does not require it, however the install must comply with the tap rules in 240.21 (C). Also, if you are in 2008 check Art 250.32, there were some changes from 05 regarding the EGC requirements and seperate structures.

 

[Ed Carr]

The panels the transformers are supplying have main breakers.
My concern was for the distance (300') and separate structures.

Ed

 

[KevinVost]

Check 240.21 (C) (2), you still may need secondary protection due to the distance the secondarys will travel (greater than 10 feet). If you want to keep it simple, install OCP on the secondary, then size your conductors for the voltage drop. Remember to up size the EGC proportionally [as required by 250.122 (B)].

 

[Ed Carr]

Kvin, Thanks for your help. That's what I was looking for.

Ed

 

[benaround]

Ed,

Would make more sense to run the 480 3ph. to the panel location and set the transformers

there, then feed the CB in the panel. I know it's not layed out that way.

 

[KevinVost]

Ed,

Would make more sense to run the 480 3ph. to the panel location and set the transformers

there, then feed the CB in the panel. I know it's not layed out that way.

Nice, would save alot of material cost if he can do it this way. Good call.

 

[ericsherman37]

transformer answer: Optimus Prime