Sharing Ground Rods

[david]

Are you hanging your hat on 250.50

"Shall be installed and used"?

You seem to be saying it has to be installed at the pedestal location. And the instalation of the electrode would have to be for the pedestal structure.

If so are your saying no existing electrodes could be used because they are not being installed for the pedestal structure

If that is your strict reading of this section I could never use a metal well casing that supplies water to a building such as a garage, house or barn.

You may not be willing to yield to the idea that 250.50 does not care about the time line or what purpose the electrode is being installed, or for that matter, for the most part ,what it is being used for. Unless it would be one in (B) not permitted to be used as an electrode.

Well casing, tanks (such as old abandoned oil tanks, galvanized buried water tanks. Metal piping systems such as irrigation water lines.

These man made electrodes that are not built into the structure in question. Are still electrodes that would qualify under the directive shall be installed

Imo anyways

 

[jaggedben]

suppose you have a building with a CEE that is the GES for that structure.

suppose your service is located on a pole 3 feet away from the building's CEE connection.

can you use the same GES for both the pole structure and the building structure?

what if the pole is 10 feet away? 20? 50? 100?

by your logic you would need to pound two ground rods at the pole.

I agree with Larry that it's a judgement call, but if it's 50ft and the house only has rods I'm most likely saying that's too far. In the OPs case (although it wasn't clear until his followup) his subpanel is barely farther away than he's required to put his second ground rod anyway, so it just makes sense to share. But if the service were on the other side of the house, knowing grounding rods don't really do !@#$ anyway, I'm less sure.

Mind you, again, I'm not necessarily the one who would strictly enforce what I think are actually overbearing NEC grounding requirements. But if we are giving advice on what typical AHJs or inspectors require, I think we are on shaky ground saying that electrodes can be shared. The AHJs I've dealt with run the gamut from not caring to enforcing the way I'm talking about.

 

[petersonra]

Is it ok to run the gec around to the other side of the house to connect to the cee there from where the service is located? Might be a run of a couple hundred feet. How is that ok if you can't run fifty feet to a perfectly good ges?

 

[jaggedben]

Because the NEC in its infinite wisdom says that what matters is whether the GES is at the structure? I'm just telling you what I think the code says and how I've seen it interpreted. I've seen discussions about this on this forum for over a decade and I've never seen anyone argue about this before. I've also been forced to run that GEC 100ft around a house to hit a water pipe, and that same AHJ probably would have made me drive two rods at a structure 5ft away.

 

[hornetd]

250.32. The separate structure needs its own GES.

My question is "Is a free standing panel support, such as a factory made service pedestal or a site built mounting board, a separate structure for the purpose of that requirement.

Manufactured Buildings often have a pedestal mounted Service Disconnect as little as 5 feet and as much as 25 feet away. Now that many of the manufacturers are installing Service Equipment in or on these structures this is becoming less common but it still being done in some cases. Obviously, at least to me, a service disconnect on a pedestal is not electrically different than one mounted on a sight built support. When does the manufactured building become a separate structure in this circumstance. Does any building that is supplied through a feeder which is supplied from the Service Equipment mounted off the building become a separate structure for Grounding requirements. Is there a specific distance? Is it 3 feet, 10 feet or the full 25 feet? If the pedestal is not a separate structure than neither is a site built backboard. If either supports the Service Disconnect does that really make the building they supply a separate structure.

This isn't a Gotcha question. I truly don't know. What I've seen done in a lot of manufactured home sites is that when the Service Equipment is immediately adjacent to the Manufactured Building, let's say within 5 feet, the driven rod Grounding Electrode's Grounding Electrode Conductor terminates in the Service Equipment but no second set is installed at the manufactured building a few feet away. If the required chassis bonding conductor was installed the inspector never even blinked. Put a Service Equipment pedestal at the maximum allowed separation, which I remember as 25 feet, is the manufactured building now a separate structure which requires a grounding electrode system and a building disconnect?

Tom Horne

PS: I didn't do many manufactured building services but I did a lot of service calls to manufactured homes. I installed perhaps 5 manufactured building services in 45 years in the craft. That is unless you want to count communications equipment shelters then it would be North of 200. Thinking about Communications Equipment Shelters they come as both manufactured buildings and as field built structures with the manufactured type being the male lion's share of the units I installed. I wonder how the code would treat the walk in refrigerator kits that we used to save weight on some of the Helicopter transported shelters. We treated them as sight built. In both types the Service Equipment or building disconnect were inside the shelter to protect them from tampering. Before electronically communicating metering was in use the meter was sometimes in the shelter behind a locked reading port which was flush with or recessed into the exterior wall.

TH

 

[hornetd]

250.53 (B) is what I found tonight but the code use to say something like if two electrodes were less than 6 ft apart they had to be bonded together.

If two ground rods were driven at the OP pedestal do you see anything in 250 part lll that would prevent a bond between the pedestal ground rod and the service ground rod
I will agree with your reading that the pedestal has to have a code compliant grounding electrode

Once that happens though I see nothing in 250 part III that would prevent the two systems from being bonded together

I would argue if there was four ground rods total on the same premise and they were closer than 6ft from each other they would have to be bonded together

Much depends on whether the pedestal is the location of the Service Equipment, the meter socket enclosure, or both. The US National Electric Code allows the connection of Grounding Electrode Conductors (GEC)s to the Grounded Current Carrying Conductor (neutral) at any point between the end of the utility's Grounded Conductor to the Bus Bar that is bonded to the Grounded Conductor bus bar in the Service Equipment enclosure.

With a meter socket only pedestal that would only be to the Grounded Conductor on the load side of the meter socket because the grounded conductor on the line side of the meter socket is part of the Utility's Service Lateral and it' connection to the Load side of the Meter Socket is the Demarcation Point between the utility's conductors and the premises Service Entry Conductors.

If the Pedestal is the location of both the Service Equipment and the meter socket then the Grounded Conductor Busbar would be the only place you could terminate any Grounding Electrode Conductor (GEC). The US NEC specifically allows that to be done because that bus bar is on the load side of the Grounded Conductor Disconnect which is the terminal which connects it to the. In the absence of a Grounded Conductor pole or breaker terminals to open the Grounded Conductor

If the pedestal is the location of the Service Equipment but the meter socket is located elsewhere, such as on the last utility pole as is done in some utility service areas, then according to the NEC you could terminate one or more GECs at either the Meter Socket Enclosure or the Service Equipment pedestal.

Tom Horne

 

[jaggedben]

My question is "Is a free standing panel support, such as a factory made service pedestal or a site built mounting board, a separate structure for the purpose of that requirement.

...

On a plain reading of the Article 100 definitions, it clearly is a separate structure. Note that the discussion above didn't hinge on that.

 

[hornetd]

On a plain reading of the Article 100 definitions, it clearly is a separate structure. Note that the discussion above didn't hinge on that.

Structure. That which is built or constructed, other than equipment.

How would a pedestal or self standing backboard not be equipment?

Tom Horne

 

[petersonra]

Structure. That which is built or constructed, other than equipment.

How would a pedestal or self standing backboard not be equipment?

Tom Horne

What is the definition of equipment.

 

[jaggedben]

How would a pedestal or self standing backboard not be equipment?

Generally speaking, it would not be.