Transformer secondary OCP

[journeyman0217]

I am looking at an electrical installation to a double wide construction trailer. Power comes out of a 75kva transformer and hits a non-fused disconnect about 6' away. It then runs the length of the trailer, about 50', and feeds a 150amp MBP. After going through the code book, am I correct in believing that the disconnect needs to be fused in order to protect the secondary conductors of the transformer? (it does not meet the 2 exceptions) and I didn't see anything mentioned about the distance the disconnect must be from the transformer...am I missing something?

 

[wwhitney]

If the transformer and secondary conductors are outdoors, then 240.21(C)(4) applies, and so the secondary OCPD could be 50' away. I'm not aware of any reason that the unfused disconnect in between would change that, but perhaps I am overlooking something.

Note that 240.21(C)(4)(3) says that the secondary OCPD must be at or next to "a" disconnect; that language permits other disconnects to be present. 240.21(C)(4)(4) does refer to "the disconnect"; for the installation you described, I'm not clear on whether that would necessarily be the first disconnect, the disconnect at the OCPD, or either as necessary for compliance.

Cheers, Wayne

 

[augie47]

I would think that since the installation would be compliant without the NF disconnect, having it there should pose no problem.