Isolated phase installations

[dennis ryland]

According to article 300.5, isolated phase installations are allowed in accordance with exception 2,to sec.300-5 (i). While this exception allows installations in nonmetallic raceways, or cables with a nonmetallic covering or nonmagnetic sheath... why does it not state nonmagnetic conduit instead of nonmetallic? See Article 300.20(B)FPN. Also does't article 300.5 apply only to underground installations?

 

[charlie]

Re: Isolated phase installations

300.5 does only apply to underground conductors. That means you are not permitted to use it anywhere else, as I have seen attempted.

The person who proposed this exception set up his proposal this way or the code making panel wanted it that way for some reason (maybe to exclude aluminum). If this is causing you heartburn, you could submit a proposal to the 2008 NEC when the 2005 is out. Personally, I don't see a problem with it the way it is worded now.

 

[don_resqcapt19]

Re: Isolated phase installations

Charlie,
I think that 300.3(B)(3) would permit an "isolated phase" installation in any location. I see no need for Exception #2 to 300.5(I) as this is already permitted by 300.3(B)(3). I also don't understand why the term "nonmetallic" was used as the major problems are caused when an "isolated phase" installation is attempted in a magnetic raceway. 300.3(B)(3) has it correct using the term "nonferrous".
Don

 

[charlie]

Re: Isolated phase installations

You are correct Don. I do not remember ever looking at that part of that section before. I know that I have read it before because I have taught it on several occasions. I like it better when I am right, crow doesn't taste very good.