320 amp single phase

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kelly russo

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louisiana
I installed a 320 amp single phase meter pan on a small restaurant
To reduce the load on the existing 225 amp 42 circuit distribution panel
we also installed a 200 amp 30 circuit panel
and split the load
upon inspection by local inspector he told me that a #4 ground wire was not correct even though the power company has feed this service with 250 mlcm aluminum.
I would like your opinion on this .
Thank You
 
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What size conductors are feeding the meter? Did you use double lugs in the meter pan to supply the two panels?
 
The GEC is sized by the size of the service entrance wire size. There could be different segments of service entrance wiring depending on whether its overhead or underground and where the service lateral stops. You need to deal with the largest segment, where ever it is.

Regardless of the size of the wires the POCO ran to the meter, what size runs from the meter to each panel? Since you have two panels, you need to add the size of the wire to each panel to determine and equivalent single wire area. If each set to a panel is 3/0 copper, then the equivalent single wire size is 167800 + 167800 = 336 KCMil which would require a #2 copper GEC per 250.66. If your wires are even larger, you may need a 1/0 GEC.

Your only "out" will be if your only electrodes are rods. In that case, #6 is all you ever have to run. But if you have metallic water pipes, or structural steel to ground or bond, you're going to have to use a #2 or #1/0 depending on what exact size wires have been run to the panels.

You can also use the GEC tap rule and run a #4 to each panel, but you still need a full size GEC somewhere and I don't think the water pipe and steel bonds/grounds can be done with taps.
 
By 50mlcm, do you really mean 50,000 circular mils, or was this a type-o for 500,000 circular mils?

Does your grounding electrode conductor go to metal water piping, or to ground rods?

-Jon
 
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