Bonding/Grounding Question - Service Entrance

[gcammerata]

I have a couple grounding related questions related to the attached drawing of my service entrance (which has a very typical configuration).

1. It is my understanding that the neutral should be isolated in the meter box (not physically connected to the grounded enclosure), because if the neutral and ground were tied together at the meter box as well as the main panel, loop currents would be created. is this correct?

2. Should the meter box be grounded via the grounding block that is mounted on the enclosure? If so, to where? Should it go to the grounding rods associated with the main service panel? Should it go to the grounding lugs in the main panel? If it should not be grounded, why not? The meter box is mounted to a steel building, so it is essentially being grounded indirectly through the steel of the steel building to the main panel enclosure, which is grounded through the grounding rods.

3. The meter box and the main panel are mounted to the same steel building. So they are indirectly grounded together.

4. Is there a possibility of loop currents because the steel building is grounded itself, and the grounding rods are grounded. So each would be at a slightly different ground potential level, which would create loop currents? Is this correct?

5. Should the steel building structure be grounded to the service panel grounding rods?

I have done many service entrances over the years, but this was the first that involved mounting on a steel building, which made me question some of these items. Any help would be appreciated!

Greg

 

[LarryFine]

1. It is my understanding that the neutral should be isolated in the meter box (not physically connected to the grounded enclosure), because if the neutral and ground were tied together at the meter box as well as the main panel, loop currents would be created. is this correct?

No. On the line side of the service disconnect, there is no EGC. The meter bases I'm familiar with have bonded neutral blocks. Any enclosures or raceways are considered to be part of the neutral.

2. Should the meter box be grounded via the grounding block that is mounted on the enclosure? If so, to where? Should it go to the grounding rods associated with the main service panel? Should it go to the grounding lugs in the main panel? If it should not be grounded, why not? The meter box is mounted to a steel building, so it is essentially being grounded indirectly through the steel of the steel building to the main panel enclosure, which is grounded through the grounding rods.

Again, it should be bonded to the neutral, with no additional EGCs needed.

3. The meter box and the main panel are mounted to the same steel building. So they are indirectly grounded together.

Yes they are, to no detriment. Think of the body and chassis of your car as one large conductor.

4. Is there a possibility of loop currents because the steel building is grounded itself, and the grounding rods are grounded. So each would be at a slightly different ground potential level, which would create loop currents? Is this correct?

Hopefully, the impedance of all of these interconnections render all of that metal at a single potential.

5. Should the steel building structure be grounded to the service panel grounding rods?

Connect a GEC to the building steel as if it was a grounding electrode.

I have done many service entrances over the years, but this was the first that involved mounting on a steel building, which made me question some of these items. Any help would be appreciated!

Hope your questions have been answered.

 

[roger]

What Larry said.

 

[infinity]

What is between the ground "block" and the neutral "block" in the panel? If it's just the metal enclosure the GEC needs to go to the neutral bar.

 

[gcammerata]

What is between the ground "block" and the neutral "block" in the panel? If it's just the metal enclosure the GEC needs to go to the neutral bar.

 

[gcammerata]

The attached pic is what is in the meter. There are no separate ground/neutral lugs.

 

[LarryFine]

The attached pic is what is in the meter. There are no separate ground/neutral lugs.

Then the meter base is bonded to the neutral already.

The two large terminals are for your incoming and outgoing neutral conductors, and the small lugs are for your GECs if you're allowed to land them there and want to use them.

 

[roger]

Then the meter base is bonded to the neutral terminal already.

And all that would need to be done after that is to put a Main Bonding Jumper in the Main Panel

 

[gcammerata]

Is it a requirement and/or best practice that I land a GEC on this same block (in the pic) as the neutrals? It is a triple lug, so I could have the incoming and outgoing neutral as well as the GEC. If the GEC is not typically landed on that block, then I won't bother. I guess I was just over-thinking the whole loop current possibilities.

Last question: why do some meter sockets have isolated neutral bars (mounted on plastic)?

 

[infinity]

Is it a requirement and/or best practice that I land a GEC on this same block (in the pic) as the neutrals? It is a triple lug, so I could have the incoming and outgoing neutral as well as the GEC. If the GEC is not typically landed on that block, then I won't bother. I guess I was just over-thinking the whole loop current possibilities.

Many POCO's do not allow a GEC connection in their metering equipment. If permitted that is the often easiest place to land the GEC(s).

 

[gcammerata]

Thanks to all for the valuable insights. I learn a great deal every time I post on here.