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Old 09-05-2013, 03:58 PM   #1
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Grounding and bonding of Service meter and distributor panel


Hello
I am new to the forum and I'm hoping to get some advice and help from people. I am building a cabin in Whatcom County, Washington and I am getting ready for new electrical service installation.
I am fairly confident in the installation so far but I've been reading lots of mixed information on the Grounding and Bonding and I'm hoping some people can help me out with this aspect.
I'll provide some background information and photos so please criticize if you see any issues (I'm hoping to get this inspected next week!)

BACKGROUND
The power company is Puget Sound Energy and they will be putting in 350 kcmil service entrance wires due to the length from the transformer. Based on this wire, I will be putting in 2 AWG grounding cables.

The service meter box and distributor panel (200 amp Square D Home line )are back to back installations connected by 2" x 3" long metal pipe and standard lock nuts. The lock nuts are not on any eccentric or concentric rings so I believe the meter box and panel are effectively bonded without the use of jumpers.

Here are the two images of the enclosures.

(I MADE A MISTAKE AND I HAVE TO REPLACE THE BARE NEUTRAL WIRE WITH AN INSULATED WHITE WIRE HENCE THE PHOTOEDITED WHITE NEUTRAL WIRE ):






For conductors between service meter box and distributor panel, I used 3/0 (black) wire for the two hots and 3/0 (white) wire for the neutral (hence the photo-edited white neutral)

GROUNDING
As depicted in the photo above, my intention is to run 2 AWG from:
- starting at the lug on the right side of the neutral lug
- down through the lug on the ground bus bar
- down through the bottom of the enclosure
- to two ground bars separated 6 feet apart.

QUESTION:
1) will this system be properly grounded?
2) do I need to run anything to the ground bus bar on the right side of the distributor panel?
3) what do I do with that green screw (provided by the manufacturer) that is pointed to in the photo?
4) Manufacturer provided another lug identical to the one on the left ground bus bar. What is it for? Or what do I do with it?

Any help or advice will be greatly appreciated.
Thanks

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Old 09-05-2013, 04:36 PM   #2
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Grounding and bonding of Service meter and distributor panel


Your supplementary electrode conductor just terminates to the point at the neutral connection where you show it.

No need to run through the ground lug because, once you install your bonding screw, the panel can will be bonded.

I'm not sure why you need to run an insulated neutral. (nevermind, brain fart)

To ground rods only needs to be #6.

Edit: the bonding screw goes in the hole just above where it is now. The hole is U shaped.


Last edited by wirenut1110; 09-05-2013 at 04:47 PM.
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Old 09-05-2013, 04:40 PM   #3
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Grounding and bonding of Service meter and distributor panel


You will need a bonding bushing on the panel side of your nipple since it is metal.

I would remove it and put PVC.
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Old 09-05-2013, 05:11 PM   #4
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Grounding and bonding of Service meter and distributor panel


Thanks for your quick response.

Quote:
Originally Posted by wirenut1110 View Post
To ground rods only needs to be #6.
I was reading NEC 250.66 that states that if the size of the ungrounded service entrance cable is 350 kcmil, that the required grounding electrode conductor needs to be 2 AWG. PSE will be using 350 kcmil cables to the meter box.
Am I misinterpreting this section?
Should I be looking at the table with the 3/0 conductors from service box to panel instead (so to use 4 AWG instead)?


Quote:
Originally Posted by wirenut1110 View Post
Edit: the bonding screw goes in the hole just above where it is now. The hole is U shaped.
Can you clarify which hole above? there are about thirty holes above where the bonding screw is now.
Are you referring to the U shaped hole at the very top just to the left of the screw holding the neutral bus bar in place?

Thanks again Wirenut1110
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Old 09-05-2013, 10:09 PM   #5
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Grounding and bonding of Service meter and distributor panel


As far as I can remember it goes here, where I marked in red.

You need to size the grounding electrode conductor for the size service entrance conductors for the load side of the meter, not for the POCO's wire.

250.66 is for the grounding electrode conductor(s) which is water pipe, building steel, etc.

If you don't have any of these and all you have are ground rods, all you need is a #6.

Even if you do have have metal water pipe, you can run a #4 but still # 6 to the ground rods.

Edit:Ground rods are supplementary electrodes and not required to be larger than a #6 up to, I believe, 2000 amps
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Grounding and bonding of Service meter and distributor panel-panel-1.jpg  
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Old 09-06-2013, 07:15 AM   #6
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Grounding and bonding of Service meter and distributor panel


Yeas, the main bonding screw goes at the red arrow.
You DO NOT need the green wire drawn in the picture. The panel box does this for you.
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Answers based on the 2008 & 2011 NEC.
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Old 09-06-2013, 10:13 AM   #7
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Grounding and bonding of Service meter and distributor panel


Quote:
Originally Posted by Speedy Petey View Post
Yeas, the main bonding screw goes at the red arrow.
You DO NOT need the green wire drawn in the picture. The panel box does this for you.
Speedy Petey
Do I not need to run a ground wire from the panel box to the grounding rods? I was going to run a bare ground from the terminal beside the neutral lug down to the two grounding rods in the ground.
Please elaborate.
thanks
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Old 09-06-2013, 10:33 AM   #8
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Grounding and bonding of Service meter and distributor panel


Quote:
Originally Posted by wirenut1110 View Post
No need to run through the ground lug because, once you install your bonding screw, the panel can will be bonded.
He was talking about this.

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