Bonding multiple service panels at a central location

[delsol]

I am about to estimate a job and have a bonding question.

The existing service consists of a 400 amp meter can with extra lugs for serving multiple panels. Currently, there are two panels served from the meter can (A 200 amp and a 100 amp panel, both interior) The meter can is directly behind the two interior panels, separated only by a 2x4 wall. I will be installing a 200 amp panel (exterior), which will serve the existing 100 amp panel and a new outbuilding. The grounding electrode conductors from the water main and ground rod enter the existing 200 amp panel.

My plan is to install a main bonding jumper from this existing panel to my new exterior load center. (The existing 100 amp is bonded to the existing 200 amp panel.) My interpretation is that this is one central service with multiple enclosures. Does anyone have any thoughts on this?

 

[augie47]

A couple of thoughts which you might not care for
In this area, your basic plan would not be acceptable due to 230.72 (one service disconnect inside, one outside).
Secondly, if it is acceptable to your AHJ, you need to look at 250.64(D) which addresses grounding electrode conductor connections with multiple disconnecting means. I believe you will find it is not permissible to ground one enclosure by routing to or through another.

 

[DARUSA]

250.64 F 3 will allow you to use a copper bar as a commons point.


250.64 F 3 Bonding jumper(s) from grounding electrode(s) shall be permitted to be
connected to an aluminum or copper busbar not less than 6 mm ? 50 mm (? in. ?
2 in.). The busbar shall be securely fastened and shall be installed in an accessible
location. Connections shall be made by a listed connector or by the exothermic
welding process. The grounding electrode conductor shall be permitted to be run
to the busbar. Where aluminum busbars are used, the installation shall comply
with 250.64(A).

 

[hurk27]

you might be beter if space allows, install the new 200 amp inside and save on the r-3 rated panel, large enough to handle the circuits of the 100 amp, and the 2-pole for the new out building, grounding can be as easy as running the #4 GEC to one panel and taping the other panel to this #4, then tap the ground rods if so needed to this #4 also, not only will you save on not using an r-3 panel but as augie47 pointed out you won't have to add the required disconnect (to meet 230.72) to bring up the existing panel which would also require the seperation of neutrals and grounding conductors in the existing panel. just hope you havent started the work yet

 

[delsol]

Thanks!

Thanks!

As a new member, (I just signed up yesterday) I really appreciate this access to knowledge and experience. hurk47, DARUSA, and augie47, thank you for your posts.