Grounding assistance - 320A Meter socket w 2 x 200A main panels

[dcg9381]

I'm doing a "utility installation" for a personal residence.
The design is a 320A meter socket that feeds 2 x 200A service mains.
The 320A meter socket will be wired (utility side) by the utility from a 15kv step down transformer.

I'd like a little assistance correctly grounding the meter socket and double checking my wiring of the 2 x 200A panels.


On grounding the 320A socket, the utility specifies:
"Grounding bushings shall e used on the inside of the meter socket, panel, or panels, attached to to grounding bus bar with #6 copper grounding conductor. Regular locknuts shall back them up on the outside of the meter socket, panel, or panels.

 

[Dennis Alwon]

I am closing this thread, in accordance with the Forum rules. This Forum is intended to assist professional electricians, inspectors, engineers, and other members of the electrical industry in the performance of their job-related tasks. However, if you are not an electrician or an electrical contractor, then we are not permitted to help you perform your own electrical installation work.


If I have misjudged the situation, if for example this project is related to your work, then send me a Private Message. If you can show me that I am wrong, and that you are a licensed electrician (or at least a licensed apprentice), then I will reopen your post, and offer an apology for the delay and inconvenience.

A reminder to all members, if you see a questionable post, feel free to report it by clicking the

button at the bottom left corner of the post.

 

[Dennis Alwon]

After conversation with the op I am re-opening the thread. There is a master electrician involved in this project.

 

[Dennis Alwon]

I have 2 comments and your electrician should know this--- one is the wire to the ground rod doesn't need to be any larger than a #6 no matter what size the service may be.

I just noticed you have a 10' 3/4" rod... Not sure what they can handle per NEC

Secondly, a 320 amp meter is really a 400 amp meter but only rated 320 amps for continuous loads. This is not an issue for a home so consider the service with 2-200 amp panels....

 

[Dennis Alwon]

Thirdly, unless the power company requires rigid nipples I would use pvc and forgo the bonding bushings. There is absolutely no reason to use galvanized nipples.

 

[augie47]

FWIW:
When the grounding electrode conductor is routed to ground rod(s), a #6 is the largest required by the NEC.
If you are not able to show 25ohms or less resistance, a single rod is required to be supplemented by an additional electrode.

 

[Dennis Alwon]

FWIW:
When the grounding electrode conductor is routed to ground rod(s), a #6 is the largest required by the NEC.
If you are not able to show 25ohms or less resistance, a single rod is required to be supplemented by an additional electrode.

That would be my fourth comment...LOL-- Probably needs 2 rods or 2 3/4" rmc conduits

 

[dcg9381]

I'll post photos tomorrow of how this is wired currently. The meter pedestal is not currently grounded - the panel was just set in place this weekend.
The utility company can require whatever they want here, we need to comply. I can add a 2nd rod, if that's required/recommended per NEC.
Appreciate the pre-pre-inspection from you guys.

 

[dcg9381]

Enclosed - this is meter socket is pending ground. Master electrician says this looks OK to him - let me know if you guys see anything I'm missing.

 

[augie47]

Master electrician needs to read 250.92
As Dennis mentioned in Post #5, you need grounding bushing on one end of your offset nipple between he panel & socket OR use PVC and avoid that hassle all together.
I would likely just bond my neutral bar in each panel and not bother with running a bare ground and installing ground bar but what you have is acceptable.
A #6 minimum from the meter socket to ground rod(a) ia all that's needed fro a grounding electrode unless there are other electrodes present

 

[Redcliffe]

and the 2 inch pvc coming from the bottom needs a bushing

 

[Dennis Alwon]

Enclosed - this is meter socket is pending ground. Master electrician says this looks OK to him - let me know if you guys see anything I'm missing.





View attachment 20385

This entire install is wrong. The neutrals should be bonded to the can with a bonding screw or strap. You also need to remove the bare copper conductors running thru the nipples. Install the grounding bushings and then run from the nipple to the neutral bar.

I also don't see a grounding electrode conductor.

Your bending radius on the wires in the left panel does not look compliant.

 

[shortcircuit2]

Thats a top feed meter socket...not to be fed from the bottom. Get rid of the bare ground. Bond nipples. Bond jumper in panels needed. GEC needed.

 

[dcg9381]

Master electrician needs to read 250.92
As Dennis mentioned in Post #5, you need grounding bushing on one end of your offset nipple between he panel & socket OR use PVC and avoid that hassle all together.

I believe there is a requirement for rigid nipples (power company).

Master electrician indicated that grounding bushings are necessary between panels if I used PVC between the panels (as it's non-conductive). This made sense (to me) - if the goal was to provide a conductive path between the boxes and one of them is grounded. I hear you guys saying that this is wrong. I think he (maybe) got it confused with load side:

Another POST has the same question - "...this means a steel EMT connector made up tight to an enclosure is an acceptable method of bonding service equipment together and bonding the grounding electrode conductor raceway to the enclosure. "

Suggestion was to read 250.92 - I did and found:

"Bond all metal raceways and enclosures that contain (or support) service conductors [250.92]"
"Standard locknuts, sealing locknuts, and metal bushings are not acceptable as the sole means for bonding a raceway" (line side)

I believe the applicable corrections to resolve this are, can you guys confirm or provide any other obvious suggestions:

• bonding type locknuts
• bonding bushings - on breaker box side run to ground bar

and the 2 inch pvc coming from the bottom needs a bushing

Done.

The neutrals should be bonded to the can with a bonding screw or strap.

Clarify. The meter socket panel has ground/neutral bonded and is connected a ground rod. I considered the 200A panels to be "sub panel" from the meter socket.

You also need to remove the bare copper conductors running thru the nipples. Install the grounding bushings and then run from the nipple to the neutral bar.

Use insulated #6 wire?
With grounding bushings, they run to the neutral, not the ground bar?

I also don't see a grounding electrode conductor.

Correct. It was added today. #6.

Your bending radius on the wires in the left panel does not look compliant.

Increase the radius of the 2/0 bends. IE - no "sharp" turns.

 

[shortcircuit2]

I looked up that socket and it is rated for overhead/underground. Just turn the lugs around and torque them correctly...

Is that SCH-80 PVC from below? 300.5(D)(4) & 352.10(F) or 352.12(C)

Did you place an expansion fitting to compensate for ground settlement? 300.5(J)

 

[Dennis Alwon]

I think we have gone way too far in this thread. If you have a contractor who is licensed then ask him to join the group and get this info. Quite frankly it really feels like we are showing you how to do the job and that is not allowed here.