Generator Connection Question

[darrell.ducoulombier]

We have 100 kva 480/277 gen set without a transfer switch that will be
solely used as for a temporary 480/277 200 amp main lug panel, it has a 125
amp main circuit breaker built into the gen set . The 480/ 277 200 amp panel
will be mounted in a wood structure building built with metal sheeting and
the new part of the building will be a all steel building . We also have a
small 10 kva single phase transformer 240/120 that will be hooked up to a
100 amp 240 / 120 panel . I have never been on a job that used a gen set as
a temporary service . So here I go. From main 125 amp breaker on gen set we
install 5-1/0 copper conductor , A,B,C,N,G from that point to main
distribution panel 200 main lug 480/277 panel with 100 amp 8breaker to shut
off from inside the room, then we come off a 2 pole 480 breaker 30 amp
breaker A,B,G to taps H1/H4 and H2/H3 tied together the grounding
conductor taps into the X2/X3 and the transformer case . X1/X4 go to the A,B
of the single phase panel and the neutral taps off of X3/X4 along with the
equipment ground, and the grounding conductor , in the 240 /120 volt panel
A,B,N,G the neutral and grounding bars are separate, with the grounding
conductor bonded to the bonded grounding bar. Last but not least we have a
8' x 5/8" ground rod that ties to the frame of the generator with a
mechanical copper lug and # 1 green to the frame of the gen set ,it has two
lugs on the grounded neutral bar in the gen set one has the neutral to the
480/277 panel and the other the grounding conductor from the panel. There is
also a factory jumper connected from the gen set neutral bar to the
generator as well. My question is does this all sound right and do I need to
have the grounding electrode wire running continued to the grounded bus bar
in the gen set. Not sure about it as far as grounding conductor and grounded
conductor and do I need a jumper from grounding electrode to the neutral bar
in the gen set cause now the gen set only has a equipment bonding jumper to
the grounding electrode .



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[ActionDave]

Welcome to the forum.

Generator and transformer have one place that the neutral is bonded. Where that bond is located is where your earth/grounding electrode conductor lands. Everything else is treated like a sub panel.

Personally, I don't care if the neutral is bonded in the generator and at the panel since it is usually rubber cords supplying the power, but you already have the five wires so you might as well use them properly.

250.30 explains it all pretty well. If you have a copy of the NEC Handbook there are some good illustrations that help clarify some of the text.

 

[JFletcher]

Welcome to the forum as well.

Breaking up your paragraph would make it easier to read, and pictures and/or line diagrams would help us visually where words may not adequately describe the installation.

 

[darrell.ducoulombier]

Thanks a lot for your time ,so on the load side of my first breaker ,in the gen set my grounding and grounded conductor terminate on the neutral bar. The neutral bar has a factory installed jumper going to the the frame of the generator / motor . There is a copper mechanical lug on the outside of the generator where I assume they hooked the original grounding electrode conductor but i can change that and go the the same point of the neutral bonding jumper. I am assuming they put the lug there for convenience . And not have to take off all the panels that serve to protect from live parts.


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