ECN Forum Forums Code Related Discussion NEC & other Code issues 400 Amp Service

Here is how we do it

320A Meter Base
3" conduit
2 parallel sets of 4/0 aluminum URD to the transformer
Meter base is grounded to groud rods with 2/0 copper

2 parallel sets of 4/0 aluminium SEU to each 200A Panel

each panel has 4ga copper cold water ground

I have found that parallel aluminum is alot cheaper than non parallel copper

Why?

6 CU or 4 AL is the largest conductor the NEC requires to run to a ground rod regardless of service size.

why 2/0 to ground rod? .....

thanks for pointing that max 4ga out. I always just looked at the grounding conductor size chart in NEC Table 250-94 and based it on the largest equivalent service entrance conductor size like the notes say.

Where do you find in NEC the 4ga max? and how does it relate to 250-94. This will save me some money.

Try 250.66
(A) Connections to Rod, Pipe, or Plate Electrodes. Where the grounding electrode conductor is connected to rod, pipe, or plate electrodes as permitted in 250.52(A)(5) or 250.52(A)(6), that portion of the conductor that is the sole connection to the grounding electrode shall not be required to be larger than 6 AWG copper wire or 4 AWG aluminum wire.
(B) Connections to Concrete-Encased Electrodes. Where the grounding electrode conductor is connected to a concrete-encased electrode as permitted in 250.52(A)(3), that portion of the conductor that is the sole connection to the grounding electrode shall not be required to be larger than 4 AWG copper wire.

Iwire, what I was refering to was the 5-gang meter socket has 3 termination points for the line side, with one set of lugs that can be moved, depending where you enter the meter socket. If I am not mistaken there is a label on the meter socket stating that the other two termination points are not for feed thru. Why would the POCO require a 200a meter socket, even if there is only a 100-a panel.

I misspoke, remember this was not my service.

The power company requires a lever bypass which results in a 200 socket.

Thanks gfretwell,

I see that is an exception to 250-94. My mistake. From now on #6 copper.