Ground Wire: Meter Socket to Panel

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  #1  
Old 08-27-12, 06:29 AM
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Ground Wire: Meter Socket to Panel

Hello,

I'm installing a meter socket with a 200 amp breaker. The socket is connected to the panel by a ~6' 2" conduit run and an LR.

Does the ground wire need a separate conduit run or can it go in the same pipe as the service wires?

On a separate note, I'll be using 2/0 or 3/0 copper wire from the weatherhead to the socket in 2" rigid (need to double check with the inspector what he wants 2008 NEC).
The breaker is factory connected to the socket plug.

From the breaker to the panel, will I be using the same gauge wire that I'm using from the weatherhead to the socket (2/0 or 3/0), or is slightly smaller wire used?

Thanks!
 
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Old 08-27-12, 06:33 AM
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Are you asking if conduit is needed for the wire going to the ground rod or something else?

The wires will be the same size from the meter to the panel.
 
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Old 08-27-12, 06:35 AM
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Wow! Thanks for the FAST reply!

I'm asking if the ground wire from the socket to the panel can be in the SAME 2" conduit as the 2 hots and neutral, or does it need to be in it's own conduit?
 
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Old 08-27-12, 07:03 AM
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Does your utility allow grounding in the meter socket? Is this a meter/main combination?

Sorry for all the questions, but want to make sure you get accurate info. normally between the meter and panel is a 3 wire setup, 2 hots and your neutral. Grounding occurs in the panel.
 
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Old 08-27-12, 07:06 AM
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It is a meter/disconnect (200 amp main breaker) combination. It was my understanding that grounding occurs where the main breaker is.
 
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Old 08-27-12, 10:07 AM
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It is a meter/disconnect (200 amp main breaker) combination. It was my understanding that grounding occurs where the main breaker is.
That may be correct.

Bare conductors should not be installed in conduit. If you're planning on using #6 bare copper, it can be run in open air. I should be OK from either the acorn nut on top of the ground rod or from a lay-in bonding lug in the meter/disconnect combination. It can be held to the outside of the conduit with UV-resistant cable ties to keep it from being damaged.

I think it would work to run an insulated conductor inside the conduit, but I can't figure out how that could be made continuous to the ground rod - not sure whether a 2-barrel lug inside the combo base would be acceptable...
 
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Old 08-27-12, 10:45 AM
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It's entirely possible that I'm missing something, but I think the OP is asking what wires should be run from the meter/main to the subpanel.

3 wires from weatherhead to meter/main, 4 wires from main to subpanel in the house.
Ground wire from meter/main to ground rods.
 
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Old 08-27-12, 12:51 PM
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4 wires from main to subpanel in the house.
Yes. The OP is asking about the preferred wiring method for the GEC between the meter and the subpanel.
 
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Old 08-27-12, 05:48 PM
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3 wires from weatherhead to meter/main, 4 wires from main to subpanel in the house.
Ground wire from meter/main to ground rods.
Exactly. The service entrance wiring ends at the service disconnect, the panel in the house is a subpanel. Since it's a subpanel, IIRC, 2/0 copper would satisfy code for the hot conductors and neutral and the ground could be #6 insulated copper in the same 2" conduit terminating in a separate ground bar in the panel inside the house. The grounds and neutrals in the subpanel would, of course, be isolated. Grounding of the neutral would take place at the neutral bar at the main disconnect outside; #6 copper to the ground rod and #4 copper to the water service entry into the house (not in the 2" conduit).
 
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Old 08-28-12, 06:52 AM
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Thanks for all the replies!

Ok, let me try to get this all straight:

From weatherhead to meter socket (service disconnect)
3 conductors in 2" rigid conduit: all 3/0 insulated copper, 2 hot one neutral.

In meter socket box
Two 3/0 hots connected to top of meter socket from weatherhead. Two 2/0 hots connected to main disconnect running to breaker panel.

Neutral is connected to neutral bar which, via #6 copper, is grounded by 2 earth grounding rods. The grounds are 8' 5/8" copper which are connected via #6 bare copper using clamps.

From meter socket (service disconnect) to breaker panel
4 wires all in the same 2" rigid conduit: two 2/0 insulated copper hot, one #6 insulated neutral, one #6 insulated ground .

In the breaker panel
2 hots connected to breaker lugs, neutral connected to neutral bar, ground is connected to DIFFERENT ground bar. From the ground bar #4 copper is connected to the copper plumbing pipes with a clamp for grounding.

Is this correct so far?

As long as it is insulated I can run the ground from the meter socket to the breaker panel in the same conduit as the rest of the wires.

I do have a question.

In my meter socket/main disconnect box, where the neutral connects. I have 2 huge lugs 1 for the neutral from the weatherhead and one to the breaker panel. But, I only have 1 smaller screw for ground. Don't I need 2? 1 for the wire to the grounding rods and 1 for the ground wire to the breaker panel?

If this doesn't make sense, I'll take a picture later. I have to go to work now.

Thanks again everyone for all your help/advice!!
 

Last edited by pcboss; 08-28-12 at 07:18 AM.
  #11  
Old 08-28-12, 09:21 AM
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Yes, a double lug for the two grounds at the disconnect.

neutral connected to neutral bar, ground is connected to DIFFERENT ground bar.
Yes. In addition, because the distribution panel is a subpanel, the neutrals must be made on an isolated bar and the grounds, and ground bar, must be bonded to the cabinet.
 
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Old 08-28-12, 05:55 PM
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From weatherhead to meter socket (service disconnect)
3 conductors in 2" rigid conduit: all 3/0 insulated copper, 2 hot one neutral.
In a residential 200 amp service, these can be either 2/0 copper or 4/0 aluminum. 3/0 copper is not necessary, but it can be used if you happen to already have it.

In meter socket box
Two 3/0 hots connected to top of meter socket from weatherhead. Two 2/0 hots connected to main disconnect running to breaker panel.

Neutral is connected to neutral bar which, via #6 copper, is grounded by 2 earth grounding rods. The grounds are 8' 5/8" copper which are connected via #6 bare copper using clamps.
In addition to grounding to the rods, you'll need to also ground the neutral via a #4 copper ground wire to where the water service enters the house.

From meter socket (service disconnect) to breaker panel
4 wires all in the same 2" rigid conduit: two 2/0 insulated copper hot, one #6 insulated neutral, one #6 insulated ground .
#6 is too small for the neutral, I'd make it 2/0.
 
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Old 08-29-12, 06:52 AM
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Ok, so all 2/0 hot and neutral wire both to meter socket and breaker panel; check.

Isolated neutrals... I know that the ground bar needs the isolated from the neutral bar and bonded to the panel box. Is isolated neutrals something different, or is that what mean?

The water enters my house in the basement near the floor. Can the grounding of water pipes occur off of a lug on the ground bar in the breaker panel (which is ~ 3' from the pipes)?

Double lug for grounds in the meter socket. Not sure what this means.

Here is a picture of my meter socket:
[ATTACH=CONFIG]2995[/ATTACH]

A closer look of the bottom neutral/ground lugs:
[ATTACH=CONFIG]2996[/ATTACH]

I understand that the big lugs (top and right) are for the neutrals. Top is from the weatherhead and right is to the panel.

Under these I see the receiver for the ground wire(s). There is NO bolt in there. Is there some sort of bolt that can receive 2 wires?

Thank you guys for all your help!! It is really appreciated!
 
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Old 08-29-12, 08:21 AM
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Isolated neutrals... I know that the ground bar needs the isolated from the neutral bar and bonded to the panel box. Is isolated neutrals something different, or is that what mean?
The neutrals need to be electrically isolated from the grounds and the bonded enclosure. Look for a bar from the same company that made the panel, that has insulaters that hold it off the can.

Just for shiggles, here's a bar from/for Eaton cutler-Hammer that does both. The grounds go on the lower bonded bar and the neutrals co on the upper isolated bar. Eaton ISOGROUND Insulated/Isolated Ground Assembly

Double lug for grounds in the meter socket. Not sure what this means.
This is a 2-barrel, or double, lug.

This is a 4-barrel stacker lug. I would look for one of these, sized for a range that includes both 2/0 and #6, to replace the lugs now in your meter base. The enclosure cannot be counted as part of the bond.
 
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Old 08-29-12, 08:39 AM
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I don't see why the enclosure could not be drilled to add another ground lug. Perhaps a call to the power company to see how they deal with the second EGC to the subpanels would provide some insight.
 
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Old 11-16-12, 06:20 PM
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Hi again!

So my project is moving along, I'm almost done. I ended up getting a double lug, the grounding bushing is on the panel side of the connecting raceway.

Would you guys mind taking a look at what I've done and let me know if it looks alright (connections, wires, etc.). This is just to the breaker box, I'm going to run the wires through the overhead this weekend.

Ignore the junk at the bottom of the box, it has been vacuumed out!

Thanks!

 
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Old 11-16-12, 07:11 PM
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Would you guys mind taking a look at what I've done and let me know if it looks alright (connections, wires, etc.).
That looks good. The only comment I would offer is that I like - and the inspectors around here like - to see the re-designation marking start at the very end of the insulation and run back 6".
 
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Old 11-16-12, 07:12 PM
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Assuming this is residential (I think that's what we were talking about in this thread) the service wires by 2008 NEC can be 2/0 copper; are those 2/0 or 3/0 copper. If 3/0, no problem. What I assume is a #6 ground wire entering a metal conduit down to a ground rod is a problem, it could be PVC conduit, but not metal. I usually recommend #6 bare stranded copper ground wire for this with no conduit, but securely fastened with 1-hole straps such as Jiffy 105C. I see 4 wires leaving the socket and headed to the subpanel, that's is correct, but I usually recommend the insulated ground wire be green. I don't, however, see a #4 copper ground wire to where the water service enters the house. I usually recommend a #4 bare stranded copper ground wire for this too.

the grounding bushing is on the panel side of the connecting raceway.
You should have a bonding bushing on each end of a metal connecting raceway meaning, you need one in the meter socket end too.

Does the power company have requirements over and above the 2008 NEC. Who is the power company, is it AmerenIllinois up there?
 
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Old 11-16-12, 09:52 PM
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Thanks for the replies.

By re-designation I assume you mean the colored tape? I will add some more.

The large gauge wire I'm using is 3/0 copper.

That is #6 wire going to the 1/2" emt. I'm confused by your suggestion that the conduit shouldn't be metal, because all my neighbors have metal conduit running to their ground rods. What is the concern with metal conduit?

The ground wire running to the breaker panel I will wrap with green tape.

Our water enters the house in the basement so the #4 wire will run from the ground bus bar in the breaker panel to the water pipe.

I had the inspector come do a preliminary inspection before I pulled the wire so I didn't have to buy more if he didn't like the locations. He was cool with only one bonding bushing.

Our POCO is ComEd here and I've met all their requirement in the "red book".
 
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Old 11-17-12, 07:50 AM
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I had the inspector come do a preliminary inspection before I pulled the wire so I didn't have to buy more if he didn't like the locations. He was cool with only one bonding bushing.
By all means, do what the inspector wants, but a bonding bushing on each end of the connecting metal conduit meets the code. I don't see any type of bushing on the metal conduit where the service wiring leaves the meter socket.

Our water enters the house in the basement so the #4 wire will run from the ground bus bar in the breaker panel to the water pipe.
The intent of the code is to ground the neutral at the first disconnect which is the main breaker at the meter. You are planning on just grounding the box with the #4 copper, not the neutral. Grounding the neutral from the subpanel (what you are calling the main panel) neutral bar is a code violation. The neutral bar in your panel should be kept isolated from the metal box and the ground wire (4th wire) from meter should termninate in a separate ground bar in the subpanel.

That is #6 wire going to the 1/2" emt. I'm confused by your suggestion that the conduit shouldn't be metal, because all my neighbors have metal conduit running to their ground rods. What is the concern with metal conduit?
By all means, you have to do what the AHJ wants. I'll look for a reference on this.

The large gauge wire I'm using is 3/0 copper.
The NEC only requires 2/0 copper for a 200 amp residential service, but I have no problem whatsoever using the full sized 3/0 copper. 2/0 is, however, cheaper and easier to work with. From what I recall, Madison County in your state used to require 3/0 copper (no aluminum) service wiring in rigid heavywall conduit (no service cable, no EMT and no PVC conduit). The AHJ has the authority to increase requirements by ordinance so you have to follow what they want.
 
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Old 11-17-12, 09:25 AM
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That is #6 wire going to the 1/2" emt. I'm confused by your suggestion that the conduit shouldn't be metal, because all my neighbors have metal conduit running to their ground rods. What is the concern with metal conduit?
Ok, found a reference. In this case, I may have been incorrect as you are using an insulated ground wire and not a bare one as is typical. If the wire were bare, it would be required to be bonded at each end of the metallic conduit. You can also check it at NEC 250.64(E). I believe the NEC allows an insulated ground wire to a ground rod, but I don't recommend it. From my observations, within 10 years, the fine strands in a typical #6 copperTHWN conductor corrode, turn green and break easily. I prefer a bare copper ground wire.
 
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Old 11-17-12, 04:11 PM
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Thank you so much for your input and time!

I'm still not sure about this part:

Our water enters the house in the basement so the #4 wire will run from the ground bus bar in the breaker panel to the water pipe.


The intent of the code is to ground the neutral at the first disconnect which is the main breaker at the meter. You are planning on just grounding the box with the #4 copper, not the neutral. Grounding the neutral from the subpanel (what you are calling the main panel) neutral bar is a code violation. The neutral bar in your panel should be kept isolated from the metal box and the ground wire (4th wire) from meter should termninate in a separate ground bar in the subpanel.
The neutral from the overhead service line will connect to the lug in the meter socket base (as seen in the last pic I posted, the white taped 3/0 wire).

Isn't it grounded there? From that lug (and attached double lug) the #6 wire runs into the sub panel where it is attached to a SEPARATE ground bus bar. (In the sub panel, the neutral is NOT bonded to the box.) From the separate ground bus bar the #4 wire will run to the water pipes.

Is this not correct?
 
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Old 11-17-12, 10:08 PM
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The neutral from the overhead service line will connect to the lug in the meter socket base (as seen in the last pic I posted, the white taped 3/0 wire).

Isn't it grounded there? From that lug (and attached double lug) the #6 wire runs into the sub panel where it is attached to a SEPARATE ground bus bar. (In the sub panel, the neutral is NOT bonded to the box.) From the separate ground bus bar the #4 wire will run to the water pipes.

Is this not correct?
Yes, all of that is correct - until you get to the part about connecting from the ground bar in the subpanel to the water pipe.

As I understand it, the point, and the intent, is not to add a separate earth ground to your GEC. That's complete, as you noted. Rather, the point and intent is to bond the water pipe (and you should also do this with your gas pipe, if you have one of those) to the GEC. That can only be done in compliance with code by bringing the conductor to the single bonding point in the meter base.

Check with your AHJ, of course. But you may need to add one more lug into the base.
 
  #24  
Old 11-18-12, 01:38 PM
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Ok, I'll have to do something about the water pipe connection.

As for the ground wire that goes to the ground rods, casualjoe suggested that insulated copper ground will corrode in ~10 years (I'm guessing that is due to water getting trapped between the copper and insulation.) Is there anything wrong with, after the insulated copper leaves the metal conduit, stripping the insulation and leaving it bare (not just at the acorns) the rest of the length?

Also, should I put any anti-corrosion compound on the lug connections? I've read that di-electric grease acts as an insulator. Do you guys suggest anything?

Thanks again!!!
 
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Old 11-18-12, 06:52 PM
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casualjoe suggested that insulated copper ground will corrode in ~10 years (I'm guessing that is due to water getting trapped between the copper and insulation.)
Stranded insulated wire such as THHN/THWN has fine strands versus 7 strand bare ground wire. What I observed was corrosion on the fine strands at the ground rod clamp. No, this has nothing to do with water being trapped between the strands and the insulation. Although insulated wire is allowed as a ground, I wouldn't use it and would use either solid or stranded bare copper ground wire. I prefer stranded because it is easier to route neatly than solid ground wire.

should I put any anti-corrosion compound on the lug connections?
I normally only suggest that on aluminum connections, but in this case it might be a good idea. If you go this route, be sure the product you use is for either ALL electrical connections or specifically copper connections. Some antioxidant compounds for aluminum are not formulated for use on copper connections. Here is a good one.

CP8-TB Thomas & Betts Kopr-Shield Compound, 8-Oz

Here is one that can be used on copper or aluminum and less expensive.

CTB8 Thomas & Betts Contax Oxide Inhibiting Compound, 8-Oz
 
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