400 Amp Meter Combo to two 200 Amp Panels

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jelatime

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Location
Greenville, SC
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Engineer
In conjunction with converting my overhead service to underground service, I'm consolidating my garage (100A) and home (150A) meters/service to a single 400A meter/combo on the house, with feeders to a new 200A panel in the house and a new 200A panel in the detached garage. I'll be meeting with the inspector shortly and would prefer to work out any kinks prior to that meeting and prior to purchasing material and starting this work. I've attached a schematic of my plans. From best I can tell by reading the forums and code book...I've got all of my grounding worked out properly (House built in the 50's with no grounding). I'm not sure if the inspector will require calculations to downsize the neutral to 2/0 or to prove 180A load on the 4/0 Al...but I will provide them if he does. Is downsizing the neutral to 2/0 for 200A standard practice? Or should I just run 4/0 x 3? Neutral/ground will be bonded at the meter combo and separated at both panels.

I'm planning to run the garage feeder using 4/0-4/0-2/0-4 Al MHF (meeting RHH/RHW/USE spec) fully in 2" pvc conduit from the meter panel to the garage panel. It looks like my best option here is either XHHW or MHF but the costs are about the same and the MHF is color coded. I understand that URD would require a splice prior to entering the structure and would rather not do that.

I was planning to use 4/0-4/0-2/0 Al SEU + #6 Cu to the panel in the house...running through the crawlspace without conduit (I have the solid #6Cu from a previous job and would like to consume it). What is not clear to me is if the house feeder SEU can have a bare/uninsulated neutral or if the neutral requires insulation. I'm thinking the neutral requires insulation due to the requirement to separate the neutral and ground at the panel (bare neutral could easily contact the panel enclosure and inadvertently bond the ground to neutral). If the neutral requires insulation, does jacketed 4/0-4/0-2/0 with all conductors insulated exist? Seems like 4/0-4/0-4/0 (with uninsulated neutral) and 4/0-4/0-4/0-2/0 (with insulated neutral) is common...but not 4/0-4/0-2/0 (with insulated neutral)...or even jacketed 4/0-4/0-2/0-4 SER? Should I just use the same MHF or XHHW (in conduit) for the crawlspace run? I was trying to stay away from conduit due to the complexity of the run in the crawlspace but I can make it work if I have to. I'm assuming both MHF and XHHW would require conduit from the meter to the panel.

Please advise if you see any issues or alternate ways to accomplish what I'm trying to do. I've attached a schematic of my plans. Schematic

Thanks in advance,
Jeremy
 

Little Bill

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Tennessee NEC:2017
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I am closing this thread in accordance with forum rules. This forum is intended for use by electricians and electrical contractors, inspectors, engineers, and vendors with their job-related duties. We are not allowed to provide how-to advice to persons who are not employed in this industry, or persons who do not perform electrical installation or maintenance as part of their jobs. Engineers are welcome to participate, but only if their questions do not involve attempts to perform their own electrical installation, troubleshooting, or maintenance work.

If I have misread the situation, if for example you have an electrical contractor on board to perform the installation work, then send me a PM to explain the circumstances.
 
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