300.3(B) exception and 300.20(B)

[Jljohnson]

It has always been my understanding of these two sections that, when running feeders in seprate conduits per phase (One conduit for A phase, one for B, etc.) that ANY ferrous metal in the system, including a simple locknut, negated the exception making it mandatory to put A-B-C-N in each conduit. Am having a disagreement with a co-worker regarding this, they say the locknut is not an issue. If I understand my theory correctly, these locknuts could get pretty hot under heavy loading of the service.

Am I missing or misinterpreting something?

 

[al hildenbrand]

Am having a disagreement with a co-worker regarding this, they say the locknut is not an issue. . .
Am I missing or misinterpreting something?

Nope. If I joined you at break, I'd be solidly on your side. :thumbsup:

 

[George Stolz]

I believe locknuts are okay - there isn't much chance of making use of "cutting slots between the individual raceways" without locknuts holding the raceways in place.

I'll try to check the ROPs and ROCs tonight to see if the CMP has weighed in on this.

 

[George Stolz]

I may end up eating crow on this one.

https://www.google.com/search?hl=en...Kb9iQLDloGwCw&ved=0CDwQrQIwAA&biw=480&bih=269

The consensus seems to orbit around nonferrous locknuts having a high probability of being required to comply.

Edit to add: Tell Moe (if this goes entirely in your favor, as I suspect it will) that I am not on the hook for any beer.

 

[iwire]

Solution, cut steel out entirety,install non-ferrous threaded plate. This happens to be MI cable but it seems it could work with PVC conduit as well.

 

[George Stolz]

The box is aluminum, no problem there. The problem is the ferrous standard locknut.

 

[don_resqcapt19]

The box is aluminum, no problem there. The problem is the ferrous standard locknut.

They make aluminum locknuts.

 

[George Stolz]

Is your run of the mill 4" steel or aluminum? I've never noticed.

 

[ActionDave]

Is your run of the mill 4" steel or aluminum? I've never noticed.

Given your magnetic personality I'd have thought you would have quite a personal data base by now.

 

[rcarroll]

According to my 2008 "Mike Holt's Illustrated Guide to 101 Essential NEC Rules" book, rule #68 aluminum locknuts are required.
Can't argue with that! On this site, anyway.