2-200 amp disconnect ground wire configuration

[Gavin540]

Looking for advice from anyone who rebuilds services on the daily. In VA the status quo is a #6 cu from the disconnect, with two 8’ ground rods for a 200amp .

For a service (320 meter) that has two means of disconnect by way of 2-200 amp panels we generally will run to each ground rod unbroken and then through both disconnects. Does anyone know where I can find a description of the correct orientation. Should ea disconnect have a separate #6 to the two ground rods. Asking because one area has a inspector who said I need separate . Never have been asked for this , every other inspector always wants a continuous #6 grounding wire. Using all copper feeders -

 

[Dennis Alwon]

There are many options. If you are allowed to land the grounding electrode conductor into the meter than that is all that is needed. Your other choice would be to make a loop from one disconnect thru the 2 rods and back up to the other disconnect

 

[Gavin540]

There are many options. If you are allowed to land the grounding electrode conductor into the meter than that is all that is needed. Your other choice would be to make a loop from one disconnect thru the 2 rods and back up to the other disconnect

Thanks for the reply, we generally do loop the ground through as you described. On this project the inspector also said that running 2/0cu was undersized for the feeds from the meter to ea disconnect . He said also the bare #6cu was too small of a grounding conductor . Instead of changing our policy to comply with this one inspector I will have to have a discussion and trying to arm myself with references .Respectfully and professionally of course. But I cannot find the nec reference for ground configurations for 400amp services with two main panels.

 

[infinity]

The GEC to a ground rod never needs to be larger than #6. What type of structure? For an SFD #2/0 Cu can be used for 200 amps.

 

[augie47]

If you have 2/0 Cu from the meter base to each 200 amp panel, even though it's widely accepted it is at times turned down with reason.
It is a 175 amp conductor and the 310.15(B)(7) rule that allows it on a 200 amp panel only applies when then conductor is supplying the the entire load of the dwelling. In your case, neither 2/0 is supplying the entire load by itself.

Does your #6 connect to anything other than the ground rods ?

 

[Gavin540]

If you have 2/0 Cu from the meter base to each 200 amp panel, even though it's widely accepted it is at times turned down with reason.
It is a 175 amp conductor and the 310.15(B)(7) rule that allows it on a 200 amp panel only applies when then conductor is supplying the the entire load of the dwelling. In your case, neither 2/0 is supplying the entire load by itself.

Does your #6 connect to anything other than the ground rods ?

We use thhn so 90 degree , 2/0 cu 195amps . I understand the reason but it’s not clear enough for me to have 1 inspector reason me into a change, going to have to have the supervisor tell me indefinitely . Otherwise we do 3/0 to the disconnect then do 2/0 from disconnect to panel . I wonder if a load calculation was done then it would satisfy the inspector. It’s a single family dwelling , they had 4/0 sec before.

#6 goes from panel 1 through both ground rods then we added intersystem bond (for Verizon ground wire ) outside that it runs through before landing in panel 2 . House does not have ufer , does not have metal water pipes.

 

[augie47]

110.14 will not allow you to use the 90° rating of the 2/0 when terminating on a 75° device (breaker)...for your application the 2/0 is a 175 amp conductor.

 

[Gavin540]

If you have 2/0 Cu from the meter base to each 200 amp panel, even though it's widely accepted it is at times turned down with reason.
It is a 175 amp conductor and the 310.15(B)(7) rule that allows it on a 200 amp panel only applies when then conductor is supplying the the entire load of the dwelling. In your case, neither 2/0 is supplying the entire load by itself.

Does your #6 connect to anything other than the ground rods ?

“(1) For a service rated 100 through 400 amperes, the service conductors supplying the entire load associated with a one-family dwelling, or the service conductors supplying the entire load associated with an individual dwelling unit in a two-family or multifamily dwelling, shall be permitted to have an ampacity not less than 83 percent of the service rating.”

Spitballing here
“service conductors” , could mean 1 , 2, 3, 4….conductors supplying the entire load ? if it’s a multi family dwelling from 1 meter with two panels (assuming) then they would have separate conductor runs at presumably the 83 percent rating ea . I wish this portion was more conclusive lol.

 

[augie47]

Is it a multi family dwelling ? (two separate dwelling units with a panel in each) or a single dwelling unit with two panels ?

 

[Gavin540]

Is it a multi family dwelling ? (two separate dwelling units with a panel in each) or a single dwelling unit with two panels ?

Single family in this case with two panels

 

[augie47]

Single family in this case with two panels

In that case, neither panel carries the full load of the dwelling and I would agree with the inspector.
Without an unknown factor, I can't see where the #6 GEC would not be sufficient.

 

[packersparky]

Thanks for the reply, we generally do loop the ground through as you described. On this project the inspector also said that running 2/0cu was undersized for the feeds from the meter to ea disconnect . He said also the bare #6cu was too small of a grounding conductor . Instead of changing our policy to comply with this one inspector I will have to have a discussion and trying to arm myself with references .Respectfully and professionally of course. But I cannot find the nec reference for ground configurations for 400amp services with two main panels.

250.64(D)

 

[augie47]

250.64(D)

?

 

[Little Bill]

I've been allowed on a 400A (320A) service to use full size conductors to each disconnect from the meter, and the allowed reduced size from each disconnect to the panels. Reason is either panel serves the load on that panel but the SE conductors need to be full size since they carry all the load. Not saying that is actually what the code says, just what was allowed per the inspector.

 

[packersparky]

?

He said he could not find the NEC reference for grounding of services with more than one disconnect.

 

[Greentagger]

He said he could not find the NEC reference for grounding of services with more than one disconnect.

250.64(D)(1)-(3).