Placement of Grounding Rods...

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linespike

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I have a 100 amp service panel mounted inside a shop building and will be hooking up two 1/2" copper coated grounding rods over six feet apart to ground it. The #4 solid copper ground wire is running from the box through 1 1/4" PVC conduit and exiting about two feet below-grade outside.

Q1: Is 1/2" grounding rod sufficient for this application?
Q2: Can I drive the first rod approximately 6" or less away from the outside of the building?
Q3: Can I run the #4 copper wire continuously from the grounding clamp on the first rod to the next rod?
:confused:

Thanks for your help in advance,

Richard Linespike
 
Re: Placement of Grounding Rods...

#1 the rod must be 5/8" 250.52(A)(5)(b)
#2 yes
#3 yes but it only needs to be a #6 250.66(A)

Roger
 
Re: Placement of Grounding Rods...

i was taught to use #4 min to avoid arguments about protecting it.Only cost a little more and very hard to cut accidently.But yes #6 is legal
 
Re: Placement of Grounding Rods...

Jim I`m with you,Buy a roll of #4 done deal!
 
Re: Placement of Grounding Rods...

Jim and Allen, how do you guys run your GEC that would cause it to be subject to physical damage?

Don't you secure it to the structure?

When I was wiring custom homes in Fl I always sleeved it in PVC regardless, simply because it was a better looking installation IMO.

Roger
 
Re: Placement of Grounding Rods...

Roger, a listed 1/2" x 8' non-ferrous ground rod is acceptable per 250.52 (5) (b). A galvy rod must be 5/8"dia. The GEC is continuous from main system bond termination point through to both electrode direct burial clamps. A #4 x 20' rebar UFER works also but check for local AHJ preferences.

rbj, INSTALLER'S QUICK-REFERENCE HOUSE WIRING AND THE PROCESS
 
Re: Placement of Grounding Rods...

The GEC is continuous from main system bond termination point through to both electrode direct burial clamps
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There is no where in the NEC that requires that the GEC has to be continuous to both rods. remember the first conductor to the first rod is the EGC. the conductor to the second rod is only a jumper and does not have to be continuous.

gndrod While you can use a 1/2" galv. rod it must be listed in fact I was shown where most galv rods are not a true 5/8" as when they are drawn they have to draw them a little smaller for the platting and after they are plated they come up short for a true 5/8" rod.
 
Re: Placement of Grounding Rods...

Gndrod, what does an AHJ's "preference" have to do with anything? Unless it is a formal amendment, what is required by the NEC or the local addopted code is all that can be enforced.

I wasn't thinking about a listed rod in my first post, my mistake.

Roger

[ October 10, 2004, 02:04 AM: Message edited by: roger ]
 
Re: Placement of Grounding Rods...

I guess I thinking in the "2005" to much but was told at the Western confrance that it was alway's intended for 1/2" galvanized rod's to be allowed if listed but in the "2002" it just doesn't say galvanized, it just says: "or their equivalent"

(b) Electrodes of rods of iron or steel shall be at least 15.87 mm ( in.) in diameter. Stainless steel rods less than 16 mm ( in.) in diameter, nonferrous rods, or their equivalent shall be listed and shall not be less than 13 mm (? in.) in diameter.
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The "2005" does say galvanized.
 
Re: Placement of Grounding Rods...

Roger, My apologies also for such a shoddy post and not addressing the post partially to linespikes inquiry.

As far as rod hot dips its not worth spitting hairs over 5/8" diameters.

Hurk27, I'm glad you are keeping me honest, so I learn by experience too. Just so you can see why my post alludes to a continuous GEC that is not a bonding jumper (unless the remaining 6' was cut from a two rod ground electrode system that is a requirement if a 25 ohm resistance check is not made or qualified..... 250.70 states "not more than one conductor shall be connected to the ground electrode by a single clamp or fitting unless the clamp or fitting is listed for multiple conductors." I have been hit by that can of worms more than once in different AHJ's. The technicality lies in 'listed single clamps' that tie two conductor wires together at one electrode regardless of whether they are in parallel or series. (exothermic is the exception)The rational is that the integrity of the connection is easily prone to separation damage during backfill or the concrete pour. And if you are working in a new jurisdiction I bet there is a question of which preferred (sorry..change that to 'local code')NEC electrode grounding system is required.

rbj, INSTALLER'S QUICK-REFERENCE HOUSE WIRING & THE PROCESS :)
 
Re: Placement of Grounding Rods...

Originally posted by gndrod:
Just so you can see why my post alludes to a continuous GEC that is not a bonding jumper (unless the remaining 6' was cut from a two rod ground electrode system that is a requirement if a 25 ohm resistance check is not made or qualified..... 250.70 states "not more than one conductor shall be connected to the ground electrode by a single clamp or fitting unless the clamp or fitting is listed for multiple conductors." I have been hit by that can of worms more than once in different AHJ's. The technicality lies in 'listed single clamps' that tie two conductor wires together at one electrode regardless of whether they are in parallel or series. (exothermic is the exception)The rational is that the integrity of the connection is easily prone to separation damage during backfill or the concrete pour.
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I am not sure I am following you. Of course we can not use two conductors in a single type clamp. You can use two single type clamps on the first rod, one for the GEC and the other for the bonding jumper to the next rod.

Unless there is a local amendment the inspector has to accept this.


By the way have you read the Forum Rules?

Please note that advertisements, chain letters, pyramid schemes, and solicitations are inappropriate on this forum.
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Forum Rules
 
Re: Placement of Grounding Rods...

Gndrod, I've recently become interested in where the idea that you must have a continuous GEC to more than one electrode comes from. (Beleive me, you're not alone). Are you saying It's because you can't use two clamps on one electrode?

There's a thread in "Groundin and Bonding" "GEC Rod and Water Pipe" you'll have to go back about 7 days. I tried to paste a link for but I'm to stupit to figure out how.

Editted for clarity

[ October 11, 2004, 03:51 AM: Message edited by: physis ]
 
Re: Placement of Grounding Rods...

physis, Don't feel alone, I belong to the same club too. The basic point iwire makes relates to being able to bond the jumper from the initial ground rod to the second rod that will require actually two single clamps on the first rod and one on the rod spaced 6' away if the GEC has been cut short of the extra 6 ft. This would only happen in the case that the last 6' of the #4 was added after the fact of needing to meet the section 250.56 resistance requirement. Maybe I misinterpreted the original post, but the continuous GEC thread-thru comment I made comes from the practicality and ease of threading the acorn clamps on the GEC for a high integrity connection of both rods together, thus, saving installation time and the cost of an extra burial clamp to conform to the requirement of 250.70. (acorns are not listed for clamping two separate conductors together.) You can also use Jr. Weavers but clamp costs add up if you're doing a few residentials at a time. (My comment was intended to help but the wording didn't come out that way.) The flip side of using a single rod to save the extra rod cost depends on soil and moisture conditions and being able to sell off the resistance reading to the AHJ in dry soil. Most of the time we bite the bullet and run two stakes and that eliminates any questions by the AHJ. In most cases, UFER's were mostly used in the hardpan clay country. The GC would pop for the use of connecting to one #4 x 20' footing rebar and we saved on rod costs. I hope this helps.

rbj
 
Re: Placement of Grounding Rods...

iwire, Is that a residential requirement for an insulated GEC mentioned in that link? Haven't run across that requirement in the western states I've worked in. Occasionally I have run short on bare conductor and had to resort to window strip-outs but I can see where threading would be a might labor intensive.

rbj
 
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