ground rods

Status
Not open for further replies.
I have a situation where I have 3 meter bases feeding 3 seperate buildings all mounted on one pole with only one drop from the power company.
My question is if I drive ground rods for each meter would I need a total of six (2 per meter) and do I maintain a 6 foot spacing between each pair or between all 6? [*]ground rods
 

tshea

Senior Member
Location
Wisconsin
Re: ground rods

This is what I would do...2 rods 6+ ft apart, #4 from each service to the first rod, then 1 #4 continued to the 2nd rod.
 

haskindm

Senior Member
Location
Maryland
Re: ground rods

You need to have a grounding electrode system for each service, not each meter. You have one service, so you only need one grounding electrode system. Review article 250 to see what is included in the "system" (ground rods, building steel, water line, concrete encased electrode, etc.).
Review 250.32 to determine if you will also need grounding electrodes at each building.
 

charlie b

Moderator
Staff member
Location
Lockport, IL
Occupation
Retired Electrical Engineer
Re: ground rods

I think it also makes a difference whether there is a disconnect associated with each meter. If so, and I suspect it is this way, haskindm is right about only needing one Grounding Electrode System. If not, if the service disconnecting means is at each building, then I believe you would need three separate Grounding Electrode Systems.

But this brings up an interesting question. The NEC generally talks about one project at a time. You want to build this building? Then here are the rules. You want to build another building? Then here are the rules. But suppose there are two adjacent buildings under separate ownership and with separate utility drops. Suppose neither has any steel in their structure and the local water systems all use PVC pipe. Is there anything in the NEC that would prohibit them from having a common GES?
 

bphgravity

Senior Member
Location
Florida
Re: ground rods

Originally posted by charlie b:
...Is there anything in the NEC that would prohibit them from having a common GES?...
I have wondered this same thing on many occasions. We have communities here that have 5' lot lines. Many times, if the services end up on the same side of each house, it would be very easy to use one system for both services.

I don't see any sections that specifically prohibit this method. I do think you introduce possible objectionable current issues similar to those 250.58 introduce.
 

charlie b

Moderator
Staff member
Location
Lockport, IL
Occupation
Retired Electrical Engineer
Re: ground rods

That's a good point, Bryan. Looking at it that way, I don't think I would want the GES for my house connected (by wires) to the GES for my neighbor's house. I drew a couple quick sketches, and I don't think there is a path for any "objectionable current" they might have to make its way into my house. But somehow I would be irrationally comforted by the 50+ ohms (from separate ground rods) that would separate their GES from mine.
 

tshea

Senior Member
Location
Wisconsin
Re: ground rods

OOPS! Better get my reading specs on...I read 3 services not 3 meters. One service, 2 rods, 6+ ft apart, #4 to first rod, continue #4 to second rod.
If you want, you can protect #6 to the rods. I prefer #4.
 

George Stolz

Moderator
Staff member
Location
Windsor, CO NEC: 2017
Occupation
Service Manager
Re: ground rods

Originally posted by tshea:
If you want, you can protect #6 to the rods. I prefer #4.
To each his own. I protect the #6 by securing it to the surface of the structure, and hugging the riser, and then running the GEC under dirt to the rod, usually about six inches. :)

Slipstream, are the disconnects for each of the three services present at the pole? You mention meterbases but I never saw you mention a disconnect. How big are we talking?

IMO, you have one structure: a pole. You need one (or two) rods for that pole if the disconnects are located there. IMO, the three service disconnects could even be considered one service in the eyes of the NEC, depending on how it's set up.

If the service disconnects are not there, then where does the utility's equipment end? The gutter that splits up the three building's supply from the one drop would necessarily be before the meters, and generally the utility owns up to and including the meter housing, to prevent tampering.
 

mdshunk

Senior Member
Location
Right here.
Re: ground rods

Originally posted by charlie b:
That's a good point, Bryan. Looking at it that way, I don't think I would want the GES for my house connected (by wires) to the GES for my neighbor's house.
That's exactly what you get, however, when you connect your GEC to the municipal water line. I've done more than one service call in which one neighbor had an open neutral, and the neutral path was going through the water line, back in the other neighbor's GEC, and back to the transformer XO through that neighbor's neutral.
 
Status
Not open for further replies.
Top