Sharing ground rods

[keith gigabyte]

I'm doing several service upgrades to a 5 unit residential building. 2 story like a row house. It appears the building was built all at one time with block walls dividing one residence from the next. Each residence has its own entrance cable meter and connection to poco. Each residence has their own breaker box with a main. Just making sure you have any info u may need. The poco connections are spread out across building. 3 drops. One drop serves 1 service and 2 drops serve 2 services each.
My question is...can I share ground rods? 2 meters are beside each other so it would be so nice to drive my rods and connect left residence with a #6 and right residence with another #6
also my reasoning for this is the entire perimeter is asphalt so I want to keep penetrations to a minimum.
one more item...each residence has its own water line from street which i will run # 6 to on each one

 

[Smart $]

IMO, not only can you share the rods, you are required to. If you use two rods for each drop, AHJ could stretch the interpretation to having to connect all six (?) rods... or use two rods total and connect both to each of the five meters. You might want to have a discussion with AHJ beforehand.

 

[growler]

The poco connections are spread out across building. 3 drops. One drop serves 1 service and 2 drops serve 2 services each.

To me it sounds as if you have three seperate services to this building.

Where the two meters are grouped close and there is one service drop that would be a service and only need two ground rods.

I would also suggest getting with the AHJ before doing anything. One thing to consider is the service size.

 

[david]

It sounds like you have five separate buildings and i would treat them each as a separate building.

"Townhouses. Each townhouse shall be considered a
separate building IRC 2009"

 

[Smart $]

It sounds like you have five separate buildings and i would treat them each as a separate building.

"Townhouses. Each townhouse shall be considered a
separate building IRC 2009"

I don't think that'll be a problem. However, what if you have a ground rod a few feet to one side of a partition projection and another a few feet to the other side. Do one or both fall under 250.50?

 

[david]

I don't think that'll be a problem. However, what if you have a ground rod a few feet to one side of a partition projection and another a few feet to the other side. Do one or both fall under 250.50?

I guess you would have to look at each of the five single family dwellings that are attached in a row separately
to determine what electrodes exist at each building.

as far as a ground rod there are a lot of detached single family dwellings where the ground rods that make a part of a grounding electrode system for the building are in close proximity (less than six feet) to there neighbors ground rods for there neighbors building (dwelling).

 

[growler]

It sounds like you have five separate buildings and i would treat them each as a separate building.

"Townhouses. Each townhouse shall be considered a
separate building IRC 2009"

I guess you would have to look at each of the five single family dwellings that are attached in a row separately to determine what electrodes exist at each building.

That's interesting and I think I like it better that way. Easier to change out one building at a time and get the power back on if occupied. Makes bonding more simple.

I would still contact the AHJ to make sure that everyone is one the same page.

 

[keith gigabyte]

Ahj

Ahj

Meeting with ahj next week. I will try to get some photos and let you know what the outcome is.

while looking at this problem I came up with another question. Poco has pole mounted xfmr feeding 5 to 8 residences, typical in this region. Usually xfmr is grounded at pole. 220 phase to phase..110 phase to ground/neutral. So now each residence has water line ground and secondary electrodes..rod pipe plate etc. as required by nec. Now that is a lot of parallel ground paths. I reason it as equipotentail groinding but why not just water line? Why additional rods. Just never looked at it this way before. Maybe I'm way off in my thinking.

reason I bring it up...years ago I had a call for warm entrance cable. Primary cause loose neutral I'm meter base. Secondary problem was what I think was a poco loose neutral. We had 15 amps on the ground wire to water line with main off and meter pulled. Very supriZing the house was carrying poco load.

 

[ActionDave]

but why not just water line? Why additional rods. Just never looked at it this way before. Maybe I'm way off in my thinking....

Some people in the electrical industry get a huge amount of satisfaction and feel like they have made the world a better place when they drive a ground rod and hook up a wire to it. Some people in charge of the code get that same feeling by requiring ground rods.

 

[growler]

So now each residence has water line ground and secondary electrodes..rod pipe plate etc. as required by nec. Now that is a lot of parallel ground paths. I reason it as equipotentail groinding but why not just water line? Why additional rods. Just never looked at it this way before. Maybe I'm way off in my thinking.

Most of the time that water line ground (cold water) is just bonding the metal pipes.

These days most of the pipe running in from the main is of a PVC type and would not provide a ground. The real problem is that you don't know what type of water pipe there is or when it may get changed out.