Meter pan and main panel grounding

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  #1  
Old 09-18-15, 06:18 AM
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Meter pan and main panel grounding

Hello,
I am installing a meter box and a 125 amp main panel for new service on a piece of vacant land. Meter and panel will be on a post. I will run two hot and one neutral from the load side of the meter to the panel using proper size wire, conduit, etc. The utility company will hook up to the line side. But I am not sure of the grounding. I know I need two 5/8" x 8' copper ground rods spaced at least 6' apart and connected with a continuous strand of #4 copper wire (these are the county specs). But here is what I am not sure of. The electric company diagram (which doesn't show much electrical detail) appears to show the ground wire coming from the meter can (attached to the ground lug, I presume), whereas drawings from other sources show it attached to the ground bar on the main panel. One utility company (not the one that will be supplying me) says to attach the ground wire to the neutral bar on the main panel and to bond the nuetral bar to the box. There is a screw that came with the panel that will allow me to make this bond. So which is it, or are these all equivalent in terms of grounding and are simply a matter of preference?

On another note, I have a GE panel TLM1212RCUP that I will be using as my main (this is a main lug designed to be converted to a main panel). Why are there two lug connectors for the neutral bar? Just curious.
 
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Old 09-18-15, 08:06 AM
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I will run two hot and one neutral from the load side of the meter to the panel using proper size wire, conduit,
You need to run 4 wires, 2 hots, 1 neutral and 1 ground to the subpanel.

The electric company diagram (which doesn't show much electrical detail) appears to show the ground wire coming from the meter can (attached to the ground lug, I presume), whereas drawings from other sources show it attached to the ground bar on the main panel. One utility company (not the one that will be supplying me) says to attach the ground wire to the neutral bar on the main panel and to bond the nuetral bar to the box. There is a screw that came with the panel that will allow me to make this bond. So which is it,
The GEC from your ground rods must terminate on the neutral whether it be in the meter socket or on the neutral bus in the main panel. Some power companies require the GEC to terminate inside the socket and some don't. Regardless, it is the neutral that must be grounded.
 
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Old 09-18-15, 08:36 AM
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The National Electric Code states to connect the grounding electrode (ground rods) to the neutral bar of the main panel. However, some power companies prefer that connection be made in the meter can. The power company rules override the NEC in this case. My best advice in this case is you'll have to find someone at the power company who can let you know the correct answer for your region.
 
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Old 09-18-15, 09:06 AM
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OK, thanks. The utility company wants the ground to come from the meter can. So how does the ground wire run between the meter can and the panel? Does it run from the neutral lug on the meter can to the neutral lug on the panel? If that's the case then there would be two wires connected to the panel neutral, the ground and the load side neutral. Yes? Where on the neutral would this ground wire attach? Just to any one of the neutral bar lugs?

And what kind of wire would that ground be? Would I run an insulated copper wire of appropriate guage through the same conduit as the two hot and one neutral? Or a bare copper wire that leaves the meter box and enters the main panel on its own?

Thanks.
 
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Old 09-18-15, 09:12 AM
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In that case you'll only need three wires between the meter and the main panel [hot-hot-neutral]. The main panel is grounded to the earth via the neutral to the meter can. The main panel should have the bonding screw or strap installed which connects the metal box to the neutral bar.
 
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Old 09-18-15, 09:33 AM
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OK, I think I got it. #4 bare copper wire from meter to grounding rods, and hot-hot-neutral from meter load lugs to panel and add bonding screw so that neutral bar in panel is bonded to the panel box. And that will complete the panel ground.

On another note, I have seen in some forums/posts etc. people sometimes use the terms bonding bar and neutral bar interchangeably, and in some cases they refer to a neutral/ground bar. But these are two distinctly different bars, why the apparent mixing of terms? Just curious.
 
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Old 09-18-15, 09:51 AM
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Hard to say, could just be unofficial terms getting crossed, could be referring to slightly different things. If you're reading code books or design manuals they will use unambiguous terms but you do need some background in the industry to interpret them. Terms like neutral and ground aren't really even used in the code or design documents because they are too general in their meaning and mean different things in different situations.
 
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Old 09-18-15, 11:43 AM
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#4 bare copper wire from meter to grounding rods
I am curious why your county requires #4 copper to the ground rods when the NEC only requires it be #6.
 
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Old 09-18-15, 12:46 PM
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Not sure why but I double checked their spec sheet and it is definitely #4. Okeechobee County, Florida. Could it be because it is going to a set of ground rods rather than plumbing or foundation rebar?

PS Thanks to everyone for their very helpful replies.
 
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Old 09-18-15, 12:50 PM
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Probably just overkill. You are in the lightning capital of the country, so it couldn't hurt I suppose.
 
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Old 09-18-15, 07:02 PM
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Could it be because it is going to a set of ground rods rather than plumbing or foundation rebar?
The NEC does require a ground connection to plumbing if the piping system is metallic and fed with metallic piping. A ufer is also required if one is available. Do the specs not mention these?
 
  #12  
Old 09-23-15, 08:05 PM
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There is no plumbing or anything else to ground to, this is a power service pole in the middle of a vacant piece of land. In this case my county code requires the meter box to be connected to two ground rods, minimum 5/8" x 8' copper (no aluminum) at least 6' apart using #4 solid copper wire. Main panel is grounded via a neutral wire bonded to main panel and connected to meter box neutral. This was made clear to me in earlier replies to this post. The information posted here also allowed me to ask my inspector some "intelligent" questions.

Anyhow, thanks to all of you I wired my stuff up and passed inspection yesterday. Thanks very much to you all.
 
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