XFMR secondary length?

[chevyx92]

Are there limits to the length of wire on the secondary side of transformers before it goes into the panel it will feed? Example 75 KVA XFMR fed from 3 phase 480v panel. Secondary 120/208v, any limit to the length of wire before it hits the panel?

 

[ryan_618]

Typically. See 240.21(C)

 

[chevyx92]

Typically. See 240.21(C)

So the max length you could have without overcurrent would be the 25 ft. rule. So lets say you had to run 50 ft. on the secondary, you have to have overcurrent protection at the secondary. Then from the overcurrent protection you can run as long you like. Did I understand that section correctly or did I miss anything?

 

[ryan_618]

I you think you got it.

 

[bdarnell]

Typically. See 240.21(C)

Then from the overcurrent protection you can run as long you like.

Once your conductors leave the OCPD, they are no longer a tap. They are a feeder, and you are correct - they can be as long as you like, all things considered.

 

[Zorch]

Keep in mind that the 25' secondary length to which you are referring is only applicable in an industrial setting. Outside of such a facility you are limited to 10' without overcurrent protection.

 

[pierre]

Zorch
Did you see 240.21(C)(6)?

 

[charlie]

Also, take a look at 240.92(B)(1)(1) for the 100 Ft tap rule. This is restricted to supervised industrial locations. :lol:

 

[Zorch]

Absolutely correct on both counts. This code section really should have been cleaned up by now.