most of my new home electrical installations i install a meter/breaker combo and run a 4 wire to the main panel. on a current job i was able to run a nearly back to back installation. (nearly meaning the meter was 3' lower than the panel)i installed meter base only and ran a 3wire to the panel. my question is..if i run the grounding electrode conductor from the rod into the meter base and then on into the panel will this constitute a parallel path for the neutral? please cite any code ref's.
thx, ken m

Ken,

Yes, this will be a parallel path, it will be a code violation since the 2 conductors in question are not the same size.310.4

Some power companies and inspectors will not allow the grounding electrode conductor to be connected in the meter base, nevermind that many meter sockets come with a lug for that purpose.

tom, thx for your reply. so the best or proper method would be to run the gec from the rod through the meter can (with no termination) ending and terminating on the grounded bus in the main panel?
thx, ken m

Ken,

In northern NJ where I inspect. the power company doesn't want the GEC inside of their meter enclousre, nor do they reay want any other wire in there or passing through it. Check sec. 250-24(a)(1) 1999 NEC where it say..."any assessible point...". The service meter technically is not assessible.

HArold

Harold,
Why isn't the meter accessible? Even a sealed meter meets the defintion of Accessible as applied to wiring methods. In this area the grounding electrode connection from a ground rod is almost always made in the meter can for a residential service.
Don

"In this area the grounding electrode connection from a ground rod is almost always made in the meter can for a residential service. "

Same here.

GJ

Harold, I have to agree with Don and GJ, the meter is accessible. I have always made this connection in the meter in residential sevices, but in all the areas I have worked, it is, or was accepted by the utility.

I would prefer this lightning braceing to be outside the house. IMHO

If you were to encounter a facility with locked electrical closets, it would probably be as, or more difficult to access the GEC. In reality when would the GEC need to be accessed?

Now back to the original question, if you are attaching the GEC to the panel, I would run it without going through the meter.

Roger

[This message has been edited by Roger (edited 12-08-2002).]

In northern Va here, the meter base is the property of the pwer company in that area and you wont be allowed to put anything other than cable intended for their use in it.period

VaSparky, isn't the GEC for their use as well as the home owners?

Roger

ken m,

You mentioned running 4 wire from meter to panel. Is this a 3W 120/240V system?

Have made some calculations where, 5 feet of RMC, EMT, Alum RMC, and RNC have been the conduits between the meter and the Main-panelboard and a #6 GEC to a ground rod from the meter and a #4 GEC from the panelboard to the water grounding electrode and assumed 25 ohms between the ground rod and the underground water electrode.

For a 200A Residential 120/240V 3W 1Ø Service and using 2/0 Copper in the raceways as noted above, for a 30 ampere unbalanced load ( where one of the Ungrounded conductors carries 30A more than the other ungrounded conductor, thus the grounded conductor [ neutral ] is carrying 30 amps) the:

RMC carries about 48 percent of the 30 Amps and the 2/0 copper about 52 percent.

EMT carries about 27 percent of the 30 Amps and the 2/0 copper about 73 percent.

The Alum RMC carries about 78 percent and the 2/0 carries about 22 percent.

and the the PVC carries 0 percent.

The grounding electrode (GE) system as noted above varied from about .003A to about .01A of the 30A parallel paths of the 2/0, the raceway(s), and the GE system.

Metallic raceways do carry an appreciable amount of the grounded conductor current on an "all" metallic raceway service installation as discribed above.

There are Many thousands of such services installed.

In many rural coops the GEC to the ground rods is connected at the drip loop to the service entry's neutral conductor. This is done for the specific purpose of shunting lightning and other surges to ground outside of the structure served. This practice was part of the service standards of the Rural Electrification Administration (REA) that set up those power cooperatives in the first place.

I still do it that way when wiring an overhead service in an exposed location such as on an open ridge top. It has confused a few inspectors who have never seen it before. In one case I had used the 2/0 flat braided copper conductor that is used for lightning down lines and until I showed him the label on the spool he would not believe it was large enough. He also did not like the fact that I ran bare number two copper from the second rod to the well casing. Once I pointed out the language in 250.64 f he was quite gracious about it even though that jurisdiction was still enforcing the 1996 NEC.

Was there any similar language in previous editions that anyone here can point me to.
--
Tom

250.64 Grounding Electrode Conductor Installation.
Grounding electrode conductors shall be installed as specified in 250.64(A) through
(F) To Electrode(s). A grounding electrode conductor shall be permitted to be run to any convenient grounding electrode available in the grounding electrode system or to one or more grounding electrode(s) individually. The grounding electrode conductor shall be sized for the largest grounding electrode conductor required among all the electrodes connected to it.

In reference to Harold's post:

My new (residential) service in Northern NJ was installed about a year and a half ago. The 2 rods are connected into the panel with the cable coming in via a separate hole in the side of the house (underground), completely separate from the meter base. (This is for an overhead service.)

Roger, I have to agree with Harold and Thinkgood. Though i realize that utility companys have their own rules and they vary widely across the country, I have always seen the power company install their own GEC to their own ground rods,almost always at the xfrmr or pole.Only one or twice have they tapped to my ground grid but that was on atleast a 250 mcm grid with a minimum of 6 rods ( 4000 amp service). A line voltage meter base ( no ct's)is never dependent on the homeowner's service panel or its ground system in this area. That leads me back to a similar question that Im always questioned on. NEC states that the neutral will be bonded at a point between the source of the derived system and its first means of overcurrent protection. If this is a house service, we bond it in the panel, even though the power company has bonded it @ the xfmr. If we're at a xfmr thats feeding a lower voltage panel ( lets say 480 to 208 ) can I legally bond it at both the xfmr AND at the first 208 panel? Given, Ill still will have the GEC to building steel at the Xfmr. Whats your input?

Locally, the utility did furnish the meter enclosurers for single meter, 200 Amps and less. They did not , as per their 'Electric Rules' did not allow the origination of a GEC from their enclosurer.
About four years ago they stopped furnishing the meter enclosures and now have removed that requirement from their 'Electric Rules'.

Now, many installer do what was done many years ago. They drop the ground rod GEC out of the meter enclosure and the (buried) Water pipe GEC out of the Panelboard.

That is the reason I noted the CURRENT on the metallic raceway between the meter and the panelboard in a previous post.

Locally, it is typically, about a 5 feet long raceway.

If Aluminum Rigid Metal Conduit (ARMC), the ARMC carries approximately 80 percent of the grounded conductor paths on a 2/0 Copper neutral conductor between the meter and the panelboard.

Don,

I have seen you on these boards for years and I highly respect your opinions. Let me offer some reasons for my opinion, If you lose your neutral at the service panel, and the supplemental grounding electrode conductor (SGEC)is attached at the meter pan, and the house has a well, with plastic pipe running out to the well. Where is the house grounded wire now? You would have 240 volts into the house with no grounded conductors. IF however the SEGC was attached to the service panel, then you might still be able to have the house function on the SEGC. I always believed that everything should be tied to gether to make up the grounding grid. Anyway you look at it, if the PoCo says no, no matter what I say, they won't hook it up. They don't want anything that isn't under their control in their meter pan.

Harold

I am a supporter of a 'single point grounding' system and also believe that such a system is not achievable when the NEC must also depend on the NESC for some of the requirements.

It will be interesting to see the ROP's for the 2005 NEC, which apparently Don has some, along the thought of ' single point grounding' or at least better definitions for Grounded, Grounding, Bonded, Bonding.

Even though the Vd (voltage drop) is very low on the metallic raceway 'in parallel' with the 'Grounded Conductor' between the meter and the Main Disconnect, the amperes carried by the metallic conduit is very high on an unbalanced 120/240V 1Ø 3W system.

Va Sparky and Harold, in commercial situations with ground rings, triads, steel coloums, rebar in slab, etc... the GEC would most likely carry the current safely, but we are talking a driven ground rod or rods here.

Lets call them what they are, placebos.

The average driven ground, even if per the NEC where a single rod would not meet 25 ohms or less, and the second rod is added, is probably just enough on any given day to inject a potentialy hazardous voltage gradient for a few feet around it.

A house would not ever safely function off of any SGEC.

Now as far as a ground rod type electrode, it is simply for lightning braceing, and not supplemental as far as sharing current flow to the MGN.

In my earlier post, , I meant that if the house took a strike, some of the voltage at this high a level would be shunted at this point, and not solely in to their equipment.

Please don't confuse my terminology of ground rod type electrode, and (for lack of better term) a true electrode as I mentioned earlier.

The service grounded conductor can be grounded as many times as you want ahead of the first disconnect, which would help.

Roger




[This message has been edited by Roger (edited 12-12-2002).]

Don,

As you know, I got a call this morning from the power company allowing the SEGC to be attached in the meter compartment. So there is no reason to fail the job because of the power company anymore, or the "assesible" rule. I also kinda agree with Roger about the "placebo" effect of 2 ground rods. I feel that if you get one ground rod down in the soil, and it is really in there good and solid, then it should be good enough. Where I inspect though, I work in 4 different towns and the soils in each town is very different. 1 town is subject to flooding, 1 town is a bottom of an old lake and it is very sandy, 1 town is very mountainous and it is very hard to get an 8 foot ground rod in the ground at all, and 1 town is a combo of mountains and soft soil. It the soft soil towns, you can almost push the ground rods in by hand 8 foot down. Is this rod good for 25 ohms? I doubt it. (Put in two rods) in the town that is all mountains, the rods go in very hard. good connection but most houses are wells, no city water connections, so 2 rods are better. The combination town also has city water, so if you get a good hard driven ground rod, the 1 rod is more than likely good enough.

Harold

i now have a different scenario from still a different county. i have a #6 bare(contractor installed) gec from the foundation rebar to the grnd elect and into the meterbase disconnect(un-spliced) i bonded the water line to the breaker panel located inside the house. the ahj said to remove the bond from disc panel and install water pipe bond to the meter base and terminate up in the meter portion of the meter/disc panel using #4 bare(which is proper for 200amp service). all your comments are very informative.
thx., ken m