Ground rods

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I'm digging the basement out in my 100yr old house & am at a point that there is no poured floor & think it would be wise to drive some ground rods for my electric service.
The current service is grounded to the city water pipe. [a 1"copper line]
I've been here 20 years and the service is probably 10 yrs older than that. There is no other ground inside or out.
The soil is wet clay - so I don't see any problem in driving a couple 8' rods.
My plan was to drive one directly under the breaker box alongside the footing - and the other 6' away. [would more distance make any difference?]
Questions- Copper is expensive, but we're only talking about <15' of wire- is bigger better? How big?
Is one ground rod connector particularly better than any others?
Should the rods be driven to current grade so when the floor is poured the connectors are below or in the concrete?
Once these are in should I remove the ground to the city water- or leave it alone?
Thanks Jim
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The rods should be a minimum of six feet apart. Acorn connectors work fine. I would leave the conductor connection above the concrete to be sure the connection is in good shape. The size of the conductor between the rods and to the service ground buss depends upon the size of the service, but #4 is suitable for any service up to 200 amp and doesn't need supplemental protection. Leave the existing water pipe ground in place as well

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6' apart is the code minimum standard, but 16' or more apart is optimum. It has something to do with the length of the rods.

#4 should suffice. Solid is cheaper than stranded, but harder to work with.

Use the Bronze acorn style and put the wire between the clamp and the rod in the V; not between the bolt on the clamp and the rod.

You could do that. You might want to have a PVC sleeve coming out of the concrete to protect the wire at floor level.

Leave the connection to the water pipe in tact. You might want to check to make sure it is tight and not corroded. If so replace it.
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Jim Elbrecht wrote:

Leave the connection to the pipes. The connection to the pipe is to ground the plumbing, not provide a ground for the electrical system.
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This is incorrect. The existing water pipe ground is indeed part of the grounding electrode system, when attached to the first five feet of entrance pipe. You'll find it in NEC 250.50 Grounding Electrode System

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True, but under current code it is not to be relied on as the primary ground, as it apparently is in the OP's house.
nate
RBM wrote:

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel
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while your upgrading grounds add jumper around meter for safetys sake. frequently meters arent good grounds because of rubber washers, and the possiblity a meter might be removed at some point
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the street supply and the home. The tech can turn off the water, remove and replace the meter, and turn the water back on in just a few minutes. The "base" ensures the ground is maintained during the servicing of the meter.
In the "bad old days" the standard electrical ground in cities was the water pipe. These are routienly "grandfathered" in.
But there is nothin against the code in putting as many ground rods as you care to and bond these rods to your service ground. There is also nothing against the "code" in connecting ("bonding") various already grounded objects.
IOW: you can have as good as any "ground" as any modern system but your "official" ground would still be the water pipe.
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John Gilmer wrote:

The "bad old days" are still here. If you read the NEC quoted in Tom Horne's post you will find water pipe (at least 10 ft buried metal) is still *required* to be used as a grounding electrode, just as it has been for a very long time.

"Modern" systems require a "supplemental" electrode because water service pipe may in the future be replaced by plastic. Ground rods were used in the past because they were easiest to install. For new construction a "concrete encased electrode" (commonly called a Ufer ground) is now usually required.

The resistance to earth of a metal municipal water system will be much lower than 1 or 2 ground rods.
--
bud--


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That N8, is why I said "part" of the grounding electrode system. Supplemental rod(s) are also required

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That depends on WHAT current code you are referring to. The 2006 IRC does in deed allow the metal underground supply pipe in contact with earth for at least 10 feet to be the sole grounding conductor.
s

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RBM wrote:

It's interesting that you place reliance on NEC 250.50 which, to my certain knowledge, has never visited the houses in my neighborhood. All the houses here have PLASTIC pipes from the city system to the houses.
Reliance on such for grounding the electrical system is foolhardy at least and fatal at best.
The pipes IN the house, however, are metal and are connected to the electrical system. It is obvious, therefore, that the purpose in so doing is to ground the pipes, not provide a ground for the electrical system.
A good rule of thumb about NEC is the dictum: "Thou shalt not worship false gods!"
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That's fine and well, but the OP's question was regarding a metal water pipe and you answer was completely wrong.

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OP:
Don't forget the meter jumper.
G P
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HeyBub wrote:

HB:
Sure it's visited. "If available". Not available, therefore you don't use it, but still must bond the pipes to grounding electrode like any other pipes. No false gods here.
G P
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HeyBub wrote:

grounding electrode. For what it is worth I will just paste the applicable code section.
250.50 Grounding Electrode System. If available on the premises at each building or structure served, each item in 250.52(A)(1) through (A)(6) shall be bonded together to form the grounding electrode system. Where none of these electrodes are available, one or more of the electrodes specified in 250.52(A)(4) through (A)(7) shall be installed and used.
250.52 Grounding Electrodes. (A) Electrodes Permitted for Grounding. (1) Metal Underground Water Pipe. A metal underground water pipe in direct contact with the earth for 3.0 m (10 ft) or more (including any metal well casing effectively bonded to the pipe) and electrically continuous (or made electrically continuous by bonding around insulating joints or insulating pipe) to the points of connection of the grounding electrode conductor and the bonding conductors. Interior metal water piping located more than 1.52 m (5 ft) from the point of entrance to the building shall not be used as a part of the grounding electrode system or as a conductor to interconnect electrodes that are part of the grounding electrode system.
Please note the use of the term SHALL. If the "Metal Underground Water Pipe" is "available on the premises" it is one of the electrodes that "shall be bonded together to form the grounding electrode system." -- Tom Horne
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Tom Horne wrote:

Apparently a religious cult.
---------------------- You said in a different thread (and different newsgroup) that a "concrete encased electrode" is not identical to a Ufer ground. What are the differences?
=bud--
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wrote:

A Yfer is a concrete encased electrode, named after George Ufer who developed the system in WWII to ground ammo dumps in the desert.
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On Thu, 27 Sep 2007 12:21:10 -0400, snipped-for-privacy@aol.com wrote:

Sorry for the typo but I had to spell Ufer phonetically in case GW was reading this forum ;-)
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bud-- wrote:

Bud A true Ufer ground is constructed of half inch or larger rebar installed in the entire foundation floor and footing. Each cross point on the rebar is double tied. A piece of rebar is turned up out of the form work at the appropriate place to make it accessible for grounding after the pour. Herbert G. Ufer developed this grounding technique to protect ammunition shelters located in the USA's western deserts from lightning during world war two. A true Ufer ground has a very low resistance to earth when compared with any other electrode other than an extensive underground metallic water system.
It was Ufer's work on the conductivity of rebar encased in concrete that is in direct contact with the soil that led to the development of the "Concrete Encased Electrode (CEE)." The latter can be as little as twenty feet of bare number four copper which is tied to the rebar only to keep it from floating up during the pour. Compared to a true Ufer ground a CEE is just a "patch off the old mans coat." -- Tom Horne
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