277 volt lighting circuits and connectors

[boltneck]

was told switch boxes containing 277v wiring with MC cable could not have the internal box clamps, but that you had to use boxes with KO's and MC connectors

didnt see anything in art 300 or 314 about that. Looking in the wrong place or looking for something thats not true?

 

[iwire]

was told switch boxes containing 277v wiring with MC cable could not have the internal box clamps, but that you had to use boxes with KO's and MC connectors

didnt see anything in art 300 or 314 about that. Looking in the wrong place or looking for something thats not true?

Perhaps a listing issue? :?

 

[cmreschke]

I've also been taught that speed lock type connectors were not rated for 277 volt circuits. Not sure if true and have not found anything to debunk this apparant myth. I do believe it would be a listing issue and not an nec issue unless violating listing requirements. Any one with any insight on this as well?

 

[augie47]

I found no restriction on the RACO site for there 155 box.
Here is a UL "General Application' guide:

http://database.ul.com/cgi-bin/XYV/...n=versionless&parent_id=1073991686&sequence=1

I'm certainly not saying there is no restriction, only I have not found one.

 

[jumper]

Unless specifically marked, I would venture that all boxes and such are rated for up to 600V just like regular building wire-NM,MC or AC.

 

[augie47]

Unless specifically marked, I would venture that all boxes and such are rated for up to 600V just like regular building wire-NM,MC or AC.

Respectfully, I look at it differently. From the wording of 250.97, if the voltages are greater than 250v to ground, the box would have to be listed for grounding if you used concentric or eccentric knockouts. I find no mention of "clamps" and can see the where the question would arise, but find nothing so far that prohibits there use on 277v

 

[iwire]

Respectfully, I look at it differently. From the wording of 250.97, if the voltages are greater than 250v to ground, the box would have to be listed for grounding if you used concentric or eccentric knockouts. I find no mention of "clamps" and can see the where the question would arise, but find nothing so far that prohibits there use on 277v

That was the angle I was thinking as well.

 

[jumper]

Respectfully, I look at it differently. From the wording of 250.97, if the voltages are greater than 250v to ground, the box would have to be listed for grounding if you used concentric or eccentric knockouts. I find no mention of "clamps" and can see the where the question would arise, but find nothing so far that prohibits there use on 277v

I was specifically talking about metal boxes and clamps only. Not enclosures, cabinets or anything else.

From your earlier link:

All boxes with concentric or eccentric knockouts have been investigated for bonding and are suitable for bonding without any additional bonding means around concentric (or eccentric) knockouts where used in circuits above or below 250 V, and may be marked as such.

Clamps for armored cable, flexible metal conduit, metal-clad interlocking armor ground cable, metal-clad continuous smooth-sheath cable, or metal-clad continuous corrugated-sheath cable are considered suitable for grounding where installed in accordance with the NEC.

 

[jumper]

Unless specifically marked, I would venture that all boxes and such are rated for up to 600V just like regular building wire-NM,MC or AC.

I see the problem, the word "such".

I meant "such" to mean clamps, washers, covers, connectors, couplings, extension rings, etc.