what does "effectively separated" mean

[mshields]

300.3(C)2 says that conductors rated over 1000 volts need to be separate from those under 1000V. For manholes it says they may occupy the same space provided they are "effectively separated". There is no definition for "effectively separate" in Article 100 or else where in the NEC as far as I can tell. So what does it mean specifically? Do I need to barrier it off. Could one just run the under 600V on a separate rack in the manhole? etc. etc. etc.

 

[FionaZuppa]

see http://forums.mikeholt.com/showthread.php?t=61966

 

[rbalex]

I was right eleven years ago. ("...the NEC always assumes (correctly or not) that application of a Section is consistent with the rest of the Code.") In this case, "effective separation" is achieved by making the conductors of the various systems to be "... securely fastened to racks, insulators, or other approved supports ...". [Section 300(C)(2)(d)] "Other approved supports" would cable trays. It also assumes the installation is consistent with Article 110, Part V. (I do know about more than classified locations)

 

[mshields]

exact wording does not bear that out

exact wording does not bear that out

I'm sure you're right that this is the intent.

But it reads "are permanently and effectively separated from the conductors of the other system "AND" (not "BY") securely fastened to racks...

The meaning of which, if not the writers intent, is that "securely fastened" is an additional requirement not a definition or description of what "effectively separated" means.

But thanks,

Mike

 

[rbalex]

If you want a specific distance or method of separation, there isn't any; it isn't necessary as long as they are properly fastened and supported. If you feel you need specificity, I refer you to Section 90.1(A) [2014 NEC] or 90.1(C) [2011 NEC or earlier].

It is a common enough practice in industrial facilities, where conductors both below and above 600V are in a common manhole, to route them on opposite sides. It is more common to use separate manholes, but that is a design and not a Code issue. As mentioned before, Art 110, Part V (starting in Section 110.70) does have some further direction.

 

[mshields]

thanks

thanks

much appreciated