Generator Mounted on Cat Tractor

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wmeek

Senior Member
Location
Texas
Occupation
Electrician
I am installing a generator on a Cat Tractor that will feed a 480V panel. Question is about the ground and bonding of this system. Should I run 3 ungrounded and 1 grounded conductor and bond in panel. There will be no ground rod as this is rolling stock. I have never done a rolling stock before and am unsure of proper way to ground and bond this system.This being used for a pipeline company having welders installed on this tractor.
Please help
Thanks
 
This is qualified by 250-34 & of course 445. If the 480V panel is mounted on the generator then you do not have to ground the generator and your circuit quantity is correct. You need to meet all the criteria of 250-34(B) otherwise you must ground it. Normally a transfer switch that breaks the grounded conductor (neutral) causes a system to be ?separately derived? that in turn requires re-establishing the ground but if the generator is the only source for a building or structure it will be considered a separately derived system, even without a transfer switch, and would need to be grounded.

If you have a separately derived system then you need a 4W feeder to the 480V panel (3 ungrounded & 1 equipment ground from table 250-122) and if this is a 480/277V you need a 5W (3 ungrounded, 1 grounded same size at the ungrounded, & 1 equipment ground sized from table 250-122)
 
This is only a 480V loads. There will not be any neutral loads. Therefore I would need 3 Ungrounded, 1 Grounding (250-122) installed. Is this what you are saying. Also out of the 480V panel will be a feed to a 480V transformer to feed a 120/240 Low voltage panel.
 
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