Grounding 400a Service To 2-200a Panels

I have a grounding question.  I am installing 400a service to my new home.  We ran 350MCM wire underground thru 3" conduit from the 2ndary terminal (moped) to the house into a 320A Cooper B-Line meter.  From the meter we ran 2 sets of 4/0-4/0-2/0 thru the wall to 2-200a breaker panels ("standard practice", according to my electrical supplier).  The ground wire (#4Cu bare) from the grounding rods comes up from the ground and we're curious if there has to be a special splice connecting the ground wire to each breaker panel or can we run thru one breaker panel to then next, say by connecting the ground wire to a ground bus on one panel and running that thru to the next with #4Cu bare or #6Cu in conductor.  Different electricians are suggesting different methods and the electrical inspector is unsure, but seems to be leaning towards the "special splice". Any feedback would be appreciated.
      


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I am installing a square D 100 amp panel in a mobel home and had a question. The panel came with no seperate grounding bar only 2 connected neutrel bars and the typical hot bars. I was curious as to why some panels have seperate grounding bars (for bare copper) attached to them an some do not. Thier was a green bonding screw that said if bonding the box was necessary to screw it in the nuetrel bar and attach a wire from it to the panel box. Would it be better to attach a grounding bar directly to the panel and run a wire from it to a rod in the ground?
      
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First, my situation: I'm having a 10x16 shed built in my backyard, to be used primarily as a woodshop. I need more than a single circuit, so I know I need a subpanel and two grounding rods at least 6' apart, bonded to the subpanel with #6 bare copper wire.



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If anyone sees any other flaws or concerns with my plan, please do speak up, I want to do this right. Thanks!



Dan
      
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I'm having quite the time finding an electrician who will quote this.  Just about all of them say that what I need is to upgrade my main panel but I want to install a new main panel that is a part of the meter base outside and make my current 100A panel a sub.   Maybe you people can tell me why nobody seems to want to do this.  Here are a few shots of the existing meter (note what is apparently a 60A base here)






and a shot of the conduit headed underground.  Like most homes built during this era, the conduit makes a right turn underground to enter through the cinderblock, ending up coming into the back of the main panel.  This conduit encloses a 4 wire feed. edit: no, actually it is only a 3 wire feed which is a problem if I want to convert the original main panel a sub.






Here's the existing panel.  It's a 60's era Square-D split panel with a 30 amp sub panel for the finished basement.  Those are low voltage wires to circuit taps for my home energy monitoring system btw.






The reason I don't want to upgrade this panel are as follows:

We won't be expanding the electrical west of this panel any more.  All planned expansion (240v car charger in Garage, planned 3 season room with grid tie Solar on the roof) will be to the east.


Upgrading the panel will require major surgery to the walls.  Due to the way the original basement is engineered there, the walls have an intricate stud pattern behind the existing panel.  I'd pretty much have to rip out a 4' section and redo it to make the access large enough to handle a 200A panel.


Adding additional circuits to an upgraded panel will require an act of God due to the finished basement construction.  There are no raceways for additional circuits.






Based on this, my thoughts were to create a new 200A main panel outside based on something like the GE model TSM420CSCUP loadcenter.  Here's a shot of this panel:






This particular panel has room for three 2-pole breakers in addition to the 200A mains.  I'd add a 100A 2-pole breaker for the existing panel, with the other two reserved for the garage/solar expansions.



The issue with the contractors who have quoted the job appears to be the conduit going to the existing panel.  I'm not sure what's wrong with it but it is apparently not compliant with current code.  Obviously the bonding needs to change, new grounding electrodes need to be driven, and a water pipe ground needs to be established to the new main panel, but what else is required?



I'd like to throughly research all the code considerations here so I can approach a contractor from a more knowledgable perspective then determine the best way to perform this upgrade.  Due to POCO coordination and the need to cut household power for the duration of the job, I have no desire to DIY this one...



So what exactly is wrong with the conduit running from the existing meter base to the existing load center?  Why is everybody telling me that I can't do essentially what I've described above?  What are the relevant code sections that will apply to this job?  Should I be chatting with my AHJ about local considerations now or should I wait until I have the code requirements down pat (assuming the latter here)?