gec for 400a service

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sd4524

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Southern California
I am installing a 400a underground service and need help sizing wire for water pipe ground and ufer ground. 250.66 uses the service entrance conductors (which the power company sizes and installs because it is underground) If the service were overhead then I would be required to install the service conductors and they would be 400. This would mean my gec would be 1/0.
However, 250.66 (B) reads that I would only need # 4 to ufer.
I'm thinking #4 to ufer and 1/0 to water pipe?
 
sd4524 said:
I am installing a 400a underground service and need help sizing wire for water pipe ground and ufer ground. 250.66 uses the service entrance conductors (which the power company sizes and installs because it is underground)
Click to expand...

That would be a service laterial, how do the wires get inside the building? those are the service entrance conductors...

Service-Entrance Conductors Underground system.

The service conductors between the terminals of the service equipment and the point of connection to the service lateral.



sd4524 said:
If the service were overhead then I would be required to install the service conductors and they would be 400. This would mean my gec would be 1/0.
However, 250.66 (B) reads that I would only need # 4 to ufer.
I'm thinking #4 to ufer and 1/0 to water pipe?
Click to expand...

I'm sure you can figure the rest out once you read my above advice.
 
On the underground residential systems that I inspect, there are never any service entrance conductors. There is only a service lateral, then the service equipment. If this is true in your case, you must do a load calculation, in accordance with the note to Table 250.66.
 
True, there will be a service LATERAL that poco installs, then service equipment. We call it a 400a "all in one" panel. I'm not sure the proper name. I read note 2 to 250.66 and believe I should size water pipe ground with 1/0.
Thanks
 
sd4524 said:
True, there will be a service LATERAL that poco installs, then service equipment. We call it a 400a "all in one" panel. I'm not sure the proper name. I read note 2 to 250.66 and believe I should size water pipe ground with 1/0.
Thanks
Click to expand...

Interesting that a 400 amp service fed with 400KCM (residential) requires a 1/0 copper GEC while a 400 amp service done with 2- 200 amp panels (3/0 copper) only requires a #2 copper Gec.
 
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