Driven Grounding Electrode For Two Panels

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newinbiz

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From the meter (400A service), I am installing two separately located 200A panels serving the same building (each with individual disconnects.) One panel is for an upstairs tenant, the other for a bottom level shop. Since this is two panels on one service, I am not sure of the following:

1. The location required for a driven ground rod(s)?
2. Are both panels required to have their own grounding electrodes.
3. The location of the main bonding jumper(s)?
4. The location of the equipment bonding jumper(s)?

If this was a single panel service I'd know what to do but as you can tell, this curveball has me unsure. Any help or specific code references will be immensely appreciated. Thanks

Bill
Tacoma, WA
 
Re: Driven Grounding Electrode For Two Panels

I cant give you a code reference but what I have done passed inspection.I ran a egc from the 2 rods to each service so you would have 2 ground clamps on each rod(1 for ea svc).And do the same for cold water.Run and connect these wires in your svc disc that is where all your bonding should be.
 
Re: Driven Grounding Electrode For Two Panels

My first question, is do you have two grouped 200A disconnects each of which goes to a 200A panel, or do you have two normal 200A main breaker main panels grouped together? The Service Equipment is where the first disconnects are and that is where you put the ground electrode system.

Your main bonding jumpers are in each Service Equipment disconnect and connect the neutral bus to the panel enclosure (its typically a green screw). Your equipment ground bus (if present) will most likely be solidly connected to the neutral bar and may use the same strap that the main bonding jumper screws through.

Put in two ground rods 6+ feet apart and feed them with a #6 or larger copper wire that goes to someplace where the service neutral is located. For a 400A service, you need at least a 1/0 copper neutral. In Washington, they don't allow you to run the GEC to the meter so you need to pick a location in a busway (if you used one), or in one of the panels. From this location you pick, you'll also need to run a 1/0 copper wire to the interior water piping (and where on that pipe depends on whether the pipe is metal out in the dirt or not -- grounding -vs- bonding, but its a 1/0 regardless).

I see no rule compelling you to run separate grounds to each panel as long as the neutral is 1/0 or larger. It is permissible to run a tap off the GEC to each additional service panel if you have more than one, but not required.

If you search this site and look for 320 or 400A services, you'll find this explained multiple times with multiple viewpoints. There are code sections specified in many of those articles.
 
Re: Driven Grounding Electrode For Two Panels

Bill,

keep in mind that you may be able to save a lot of money and resources by sizing your conductors to the calculated load, since you have more than one disconnect. 230.90 exception 3 allows this. Im not sure what kind of loads you are running, but it is doubtful you need all 400A. If you are able lower you service entrance conductor size, than your GEC can be smaller as well. I recently had to use a 400 A meter pan for a 225 A service (I had a 100A main and a 200A main)
Have fun.
 
Re: Driven Grounding Electrode For Two Panels

Bill,
I would like to clarify that 230.90 exception 3 would apply to one set of service entrance conductors that has more than one disconnecting means. If you run two sets of service conductors from the meter, one to each panel, you must size each based on the overcurrent device, not the load.
 
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