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#203201 - 09/14/11 09:58 AM Generator OCPDs
Helectric Offline

Registered: 01/07/05
Posts: 91
Loc: Brandon, SD
Need some help. I have a portable 7.5 KW generator on a trailer. It's used to supply power to a portable job trailer in strip mining operations. The on board panel is a replacement that consists of a 40 amp back fed main and some single pole 20s. It's been hacked up pretty good and I want to replace it.
I'm thinking of using a Midwest panel with a 30 amp back fed main. Branch breakers would be (1) 30 amp, 2 pole GFI (for job trailer)and (1) 20 amp, 1 pole GFI (for genset mounted receptacle).
This is a new one for me so any comments or suggestions would be welcome.

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#203207 - 09/14/11 11:58 AM Re: Generator OCPDs [Re: Helectric]
HotLine1 Offline


Registered: 04/03/02
Posts: 6792
Loc: Brick, NJ USA
Sounds like a plan IMHO, but I'm not 'up' on mining rules & regs.

#203220 - 09/14/11 10:07 PM Re: Generator OCPDs [Re: Helectric]
LarryC Offline

Registered: 07/05/04
Posts: 776
Loc: Winchester, NH, US
I would think that a 40 A main with a two pole 30 A GFCI and two or four single pole 20 A GFCI would be a better choice.

With a 30 A main and a 30 A GFCI, when fully loading the GFCI, you are in a race between both of the 30 A breakers.

Having two or four single pole breakers allows you to use mutiple small loads without one breaker trip making everything stop.

How do you deal with grounds and neutrals? Is the centertap of the generator windings tied to the generator frame? Is the generator frame bonded to the trailer frame? Do you drive ground rods or drag chains?

What does MSA state about temporary portable power for strip mines?


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