400a Double panel Service question.

[JohnDS]

Hey guys,
Just need a refresh here.

400 amp service: 1 meter and 2) 200amp panels located within 5' of meter.
Using 2) 2/0 SEU's going to each panel from meter.

What is the proper way to ground this. This is what I was thinking:

2) #4 solid bear copper grounding electrodes. 1 going from each panel to water main.

2) #6 solid bear copper grounds. 1 going from each panel to it's own ground rod
(2 ground rods total 6'min apart from eachother)


If there is a better way or something wrong here, please let me know. I believe I can use one big grounding electrode and then just jump the panels, but I don't have my book handy. Worse case scenario, would 2 separate #4's be fine?

 

[Dennis Alwon]

400 amp service: 1 meter and 2) 200amp panels located within 5' of meter.
Using 2) 2/0 SEU's going to each panel from meter.

IMO, this is a violation 3/0 is needed.

What is the proper way to ground this. This is what I was thinking:

2) #4 solid bear copper grounding electrodes. 1 going from each panel to water main.

I believe this is a violation also. I would run #2 to the meter if that is allowed otherwise #2 to one panel and tap to the other.

2) #6 solid bear copper grounds. 1 going from each panel to it's own ground rod
(2 ground rods total 6'min apart from eachother)

Strike three... you could do this but you need a jumper between the rods.

Let's see what others say.

 

[JohnDS]

IMO, this is a violation 3/0 is needed.

What is the proper way to ground this. This is what I was thinking:

I believe this is a violation also. I would run #2 to the meter if that is allowed otherwise #2 to one panel and tap to the other.

Strike three... you could do this but you need a jumper between the rods.

Let's see what others say.

I'm confused about your answer to the second part. Just so we are on the same page, you are saying meter, like "water meter"?

 

[Dennis Alwon]

I'm confused about your answer to the second part. Just so we are on the same page, you are saying meter, like "water meter"?

No, the electric meter. Go from the electric meter to the water pipe with #2 and be done.

 

[JohnDS]

No, the electric meter. Go from the electric meter to the water pipe with #2 and be done.

Hmmm. Yea I'll check that out but I'm honestly not sure if that's allowed. I've never seen anyone do it that way. I have seen people run from 1 panel to water main and jump the other panel though....maybe I'll go with that to be safe.


As for the other 2 answers. Please don't take me the wrong way here as I am more questioning you to understand why.

The 3/0:...Doesn't a 200a service call for 2/0 copper?

The jumper" between ground rods:...is that strictly for a double service/single meter application?

Because I remember I did a temporary single 200a service for a new house that did not have a water-main yet, and I installed two ground rods with no jumper, and the inspector did not have a problem with that.

 

[augie47]

I'm with Dennis (partly).
Common practice here would be a GEC from the meter. #6 to ground rod(s), #4 to a CEE, and #1/0 to the water.
If any of those are run from the panel(s) instead you could elect to run one GEC from each panel.
You would need a #4 to water from each or a 1/0 common, tapped with #4s.
If you do use two ground rods, in my opinion, they would need to be tied together.

In regard to the 2/0, your AHJ may allow it, but under the '08 Code 2/0 is only allowed for "whole house" services/feeders. Since you have two service panels, by NEC it should be sized be 310.16.

 

[infinity]

I would run one GEC to the water pipe based on the size of the conductors feeding the meter and tap off to each service disconnect with a #4 Cu conductor and a split bolt. This is from the 2008 NECH:

 

[JohnDS]

I'm with Dennis (partly).
Common practice here would be a GEC from the meter. #6 to ground rod(s), #4 to a CEE, and #1/0 to the water.
If any of those are run from the panel(s) instead you could elect to run one GEC from each panel.
You would need a #4 to water from each or a 1/0 common, tapped with #4s.
If you do use two ground rods, in my opinion, they would need to be tied together.

In regard to the 2/0, your AHJ may allow it, but under the '08 Code 2/0 is only allowed for "whole house" services/feeders. Since you have two service panels, by NEC it should be sized be 310.16.

I just wanted to point out here that I am talking about a single phase residential service that has the main breaker in each panel if that changes anything.


Ok so just to clear things up because I'm a little confused still, this can be done one of these 3 ways?:

A) 1 #4 from each panel to water main and 1 #6 from each panel to it's own ground rod, and connect the two with #6.

or

B) 1 #1/0 from one panel to water main, connect two panels with #4, and 2 #6 from each panel to it's own ground rod and connect the two with #6.

or

C) Not sure what you meant in the second sentence. Everything is coming from the meter? the #6's to ground rods, 1/0 to water main, and #4 to CEE(what is CEE please)?

 

[augie47]

Again your AHJ may accept a 2/0 to each panel, but, technically, the 2/0 allowance is for a "whole house" feeder (singular)... not two feeders to two panels.

CEE is concrete encased electrode or footer ground. Required if present.

 

[JohnDS]

Again your AHJ may accept a 2/0 to each panel, but, technically, the 2/0 allowance is for a "whole house" feeder (singular)... not two feeders to two panels.

CEE is concrete encased electrode or footer ground. Required if present.

Thanks guys. Aside from that, is that a yes to A) and B)?

 

[augie47]

Yep...................................

 

[Dennis Alwon]

I should have read further that a #4 from each panel is acceptable--never did that-- 250.64(D)(2).

I have to say that if you have 2 - 200 amp panels with 3/0 copper than a #2 is all that is required for the water main not 1/0. I am assuming copper since no one mentioned aluminum.

250.66 Note #1
3/0 = 167,800 cir. mill x 2= 335,600 cir mil.

Again Table 250.66 Over 3/0 thru 350,000 states #2 copper.