EGC vs Bound to ground ring

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kenaslan

Senior Member
Location
Billings MT
I have a 4160V motor with full size EGC back to the MV motor starter. I also have a ground wire from the frame to the buried ground grid. Is this grounding wire to be sized via what table?
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I have a 4160V motor with full size EGC back to the MV motor starter. I also have a ground wire from the frame to the buried ground grid. Is this grounding wire to be sized via what table?

Is this required by code? If not, then the code is not much help since it only covers things that are required.
 

Smart $

Esteemed Member
Location
Ohio
You may get a few different answers, because it is not required. IMO if you bond it to the grounding grid, the jumper needs to be sized per 250.122 at a minimum because is on the load side of an overcurrent device.

Some facilities have a minimum bonding jumper spec. I've worked at several power plants that had a minimum size of 4/0 solid copper for skids to grounding grid jumpers.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
There is nothing in that section that requires the wire from the equipment to the grounding grid that you were asking about sizing.
250.100 Bonding in Hazardous (Classified) Locations Regardless of the voltage of the electrical system, the electrical continuity of non?current-carrying met al parts of equipment, raceways, and other enclosures in any hazardous (classified) location, as defined in 500.5, 505.5, and 506.5, shall be ensured by any of the bonding methods specified in 250.92(B)(2) through (B)(4). One or more of these bonding methods shall be used whether or not equipment grounding conductors of the wire type are installed.
 
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