Bonding boxes at 480v?

[ritelec]

Hello,

"Several" years back, new requirements for bonding boxes at 277/480 ( maybe even 208 or 240v ?.. though I think just 480) with concentric and eccentric ko's was required via grounding bushings.


I vaguely remember a Mike Holt cartoon that spelled it all out.

I will look for the pic or reading through the book but any direction would be great.

Thank you

 

[ritelec]

Sorry nevermind?got it, 250.97

 

[augie47]

Note the wording in the exception:" where a box or enclosure with concentric or eccentric knockouts is listed for the purpose".
A vast majority of you boxes are so listed.

 

[ritelec]

Thank you

 

[Carultch]

Hello,

"Several" years back, new requirements for bonding boxes at 277/480 ( maybe even 208 or 240v ?.. though I think just 480) with concentric and eccentric ko's was required via grounding bushings.


I vaguely remember a Mike Holt cartoon that spelled it all out.

I will look for the pic or reading through the book but any direction would be great.

Thank you

The cutoff is now generalized as 250 Volts to ground nominal.

120/208 wye
120/240 single phase
120/240 high leg delta
240 corner grounded delta

are all in the sub-250V to ground category


277/480 wye
480 delta
600 delta
600Vdc
1000Vdc

are all in the above 250V to ground category