ECN Forum
Posted By: sparky66wv Ground Rod Woes Revisited... - 10/01/02 02:02 AM
A picture is worth 1000 (curse) words...

[Linked Image from users.stargate.net]

The above pic shows the consistency of the um, "soil"... for want of a more descriptive word... The groundrod visible is resting upon the back-fill pile.

[Linked Image from users.stargate.net]

Shown above, one ground rod will lie in the trench at 30" deep, as far from the 1-1/2" PVC conduit as practical.

[Linked Image from users.stargate.net]

The second rod will be in the as yet non-existent trench, which will extend another 15' from the end of the existing one.

How would you tackle this?

Does your PoCo accept Ufers, plates, rings or other electrodes? If not by default, how do you gain acceptance of alternate means?

This is but the first of many possible services I'll do in the general area of these photos, so I'll be tackling this problem many times. Large, powerful, and dangerous machines and methods will also be considered!

[This message has been edited by sparky66wv (edited 09-30-2002).]
Posted By: txsparky Re: Ground Rod Woes Revisited... - 10/01/02 10:48 PM
Where I'm at,we have sand or clay or any combination in-between.Haven't had to deal with rock.None of the PoCos I deal with(5 different ones) would ever know to look for a second rod.Can you drive a rod there with a roto-hammer?I asked because I noticed someone was able to auger in the trailer tie down rods(Hmmm.... I wonder....nah)Anyhoo,what are you doing your trenches with now?That trailers gonna need water and sewer;any chance of working something out with the plumbers? I've gotten many a trench dug for a case or two of their favorite beverage [Linked Image]
Posted By: sparky66wv Re: Ground Rod Woes Revisited... - 10/01/02 11:08 PM
I've tried a rotary-hammer once and wasn't very impressed. The combination I was using may have had something to do with it. I had better luck with a sledge. The rotary hammer was one of the big bosch's, can't remember the #... SDS Max, I believe. I'd used it to core drill a 2" hole and figured, that since I'd paid the damage waiver on the rental, I'd give driving a rod a shot. (I know, that probably wasn't a cool thing to do...)

It didn't work well.

The only thing that has actually impressed me is a Bosch electric jack hammer. But I ain't liftin' 90 lbs eight feet up! Besides, they're a couple grand I think!

Would a ground plate require a smaller hole, and would it offer less resistance/impedance and be a more effective electrode?

What about Ufers?

Txsparky, No problem on this particular one, the trench was extended and back filled today. Plus this installion will only be here about a year. Since this is a future golf course, (the Greenbrier) I'm trying to plan for better grounding options if/when the time comes and I'm called upon. I'm just trying to explore more options for the not-too-distant future, but I want to really offer electrodes that work.

Am I right to assume that ground rods are practically useless in these soil conditions?

[This message has been edited by sparky66wv (edited 10-01-2002).]
Posted By: Bjarney Re: Ground Rod Woes Revisited... - 10/02/02 12:24 AM
Shot from the hip, but any chance a chemical rod/counterpoise would do the job? http://www.lyncole.com/html/Rod.asp#lshaped
Posted By: Fred Re: Ground Rod Woes Revisited... - 10/02/02 12:39 AM
Sparkywv,
I've went to Ufer grounds everywhere in the last 2 years. It took some educating of the local inspectors but it's worth it. It does make the telephone guys mad that they don't have my ground rod to tag on to but that's life. It can be such a crap shoot when driving a rod around here. It always seems like the drains, gas line sleeve or water line ends up in the same corner as the UG service does and it's a gamble to start ramming 8' of anything in the ground there. Not to mention what nature or someone has burried there. I did a new house once and couldn't get anything deeper than 3'. The excavator who dug the foundation later told me he uncovered 6'x10' sections of concrete sidewalk. The building site had once been a dumpsite for the city when they re-did Main Street. On a rural new home job that had been a farm years ago, the excavator dug up a 1947 Plymouth sedan while digging the basement for the new house!
Ufers all the way!
Posted By: sparky Re: Ground Rod Woes Revisited... - 10/02/02 01:09 AM
to be honest Virgil
i can rarely cut 250.53(G), save for an 'oblique' angle myself.... (puff...puff..pant...)

aw, just throw 'em in the ditch...
[Linked Image]

Quote
What about Ufers?

well, the NEC does not quite come out and say it, but 250.52(A)(3)sounds Uferish ....
it almost sounds as if the 1-7 are in order of preference....

Quote
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.

Quote
Formal Interpretation 78-4
Reference: Article 250.50
Question: Is it the intent of 250.50 that reinforcing steel, if used in a building footing, must be made available for grounding?
Answer: No.
Issue Edition: 1978
Reference: 250-81
Issue Date: March 1980

right... ever try convincing the concrete dudes? i just did a ufer last month, & was dubbed loco sparky'......

now the poco engineers recognize the efficy , seems the linecrew traditionally look for rods..... i guess you'll need to talk to the poco boss..
[Linked Image]
sometimes a 250.52(A)(4) "ground ring" is spec'd out by architects. i just don't know how to 'encircle' a structure with only 20' though...

Quote
Am I right to assume that ground rods are practically useless in these soil conditions?

comparitively i'd vote yes, useless...

i'm sure there's a Soares ditty about the efficy of 'made' electrodes, i've heard of some who drive excessive depths and/or distances apart to achieve a decent ohmic value.

I also heard the IAEI did a study....

[Linked Image]

[This message has been edited due to blistered fingers}

[This message has been edited by sparky (edited 10-01-2002).]
Posted By: HotLine1 Re: Ground Rod Woes Revisited... - 10/02/02 01:13 AM
Hey 66
I have to ask....what the x@#$ is a "ufer"
Some of us boys up here in the "cities" ain't heard of that.

In a serious note; what is a ufer???

John
Posted By: sparky Re: Ground Rod Woes Revisited... - 10/02/02 01:16 AM
Quote
excavator dug up a 1947 Plymouth

no, no... Fred, put it back....i can make it work..
[Linked Image]

(7) Other Local Metal Underground Systems or Structures. Other local metal underground systems or structures such as piping systems and underground tanks.
Posted By: sparky Re: Ground Rod Woes Revisited... - 10/02/02 01:18 AM
read here John
[Linked Image]
Posted By: sparky66wv Re: Ground Rod Woes Revisited... - 10/02/02 03:12 AM
Beej, as a last resort, I've had to make my own L-shaped rods (good 'ol MAP gas!) after hitting limestone or granite. The hammer gets to be like hitting a brick wall with an aluminum baseball bat! Ouch! [Linked Image] The sandstone in the pics above is relatively soft in comparison!
I could drive 'em at about 100 strokes per inch, but I'm getting to old for that crap!

I've even been crafty enough to actually dog-leg a rod so that the top of it looks like it's going straight down, just in case the AHJ likes it that way...

John, A Ufer is a Concrete Encased Electrode. I've never used one, but I'm told they are the default and primary grounding means in Oregon (Someone here said that, I think). So a Ufer is, what 20' of copper in atleast 2" of concrete? What size copper? Pipe, Rod or wire?

Fred, shoulda bonded to the Plymouth like Steve is eluding to! Hee hee!

[Linked Image]

Steve, gimme a minute to read all those links! You da man, BTW! (What you got, like 3100 posts or something?!!? *jealous*)

BRB...
Posted By: sparky66wv Re: Ground Rod Woes Revisited... - 10/02/02 03:25 AM
Well, I guess it comes down to:

If I gotta work so hard at getting a particular part of the service installed, I want it to be something that actually works.

What would be the cheapest and simplist, yet effective way to install a ufer with a target of say, 25 Ohms?

I need to get a "megger" don't I...

*watches $100 bills fly out the window*

Great soundbites Steve, and I've already called AP, but haven't talked to an EE yet...

Maybe tomorrow.

*...meditates saying "Ohm" and thumping self in head with the 2002 NEC...*
Posted By: stamcon Re: Ground Rod Woes Revisited... - 10/02/02 03:29 AM
Sparky66, the electrode can be at least 20 of #4 rebar in the bottom of the footing(at least 2" of concrete around it) or 20' of no smaller than bare #4 copper wire. The 20 feet is the horizontal length at the bottom and does not include the vertical portion that comes up and out of the foundation. New construction in CA requires them.
Posted By: Sean WB Re: Ground Rod Woes Revisited... - 10/02/02 03:36 AM
Hey spark,I scored a kik ass megger from ebay for $60!. They are the crank type.1000v 1000m-ohms. earth tester/megger/insulation .
not a bad deal for a guy on a budget. http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=1771774872

PS, I think you could drive a couple of 8' ground rods. looks that way from my house anyway [Linked Image]

[This message has been edited by Sean WB (edited 10-01-2002).]
Posted By: sparky66wv Re: Ground Rod Woes Revisited... - 10/02/02 03:44 AM
Sean, here's the kicker...

I don't know how to use one!

I've heard about fall-of-potential methods and the like, and I have been led to believe that the mega-expensive meggers designed for ground rods without external test rods are the most convenient.

How does one test grounding electrodes with an analog crank megger?

PS: Are you a journeyman yet, Sean? [Linked Image]


[This message has been edited by sparky66wv (edited 10-01-2002).]
Posted By: caselec Re: Ground Rod Woes Revisited... - 10/02/02 04:17 AM
Hey Virgil

You don't want a megger to test your ground rods. A megger is used to test very high resistance. You need to test for low resistance.

I just wanted to say something before you went out and spent hard earned money and discovered you purchased the wrong thing.

Curt
Posted By: sparky66wv Re: Ground Rod Woes Revisited... - 10/02/02 05:30 AM
Ahhhh!

Thanks, that makes sense...
Posted By: Electricmanscott Re: Ground Rod Woes Revisited... - 10/02/02 11:07 AM
Anyone read 250.53 A "Where practicable rod, pipe, and plate electrodes shall be embedded below permanent moisture level" What does this mean and who does this?
Posted By: tdhorne Re: Ground Rod Woes Revisited... - 10/02/02 02:03 PM
Quote
Sometimes a 250.52(A)(4) "ground ring" is spec'd out by architects. i just don't know how to 'encircle' a structure with only 20' though...


The operative phrase in that case is "at least." The reason for the restriction is that very small structures such as guard shacks and well houses could be encircled with less wire. Twenty Feet is the minimum length. The perimeter distance around most structures assures that the length will be adequate to provide a ground that is a lower impedance than the two driven rod minimum solution.

(4) Ground Ring. A ground ring encircling the building or structure, in direct contact with the earth, consisting of at least 6.0 m (20 ft) of bare copper conductor not smaller than 2 AWG.
--
Tom
Posted By: resqcapt19 Re: Ground Rod Woes Revisited... - 10/02/02 02:38 PM
The only electrodes that the code requires 25 ohms or less for are rod, pipe or plate electrodes. No testing is required by the NEC for water pipes, Ufers and building steel.
Don
Posted By: Tom Re: Ground Rod Woes Revisited... - 10/02/02 08:46 PM
Virgil,

Don't waste your $$ on a ground resistance tester. It is unlikely that you will find anyplace in WV that you can get 25 ohms or less, except maybe the bed of the Ohio or Potomoc river.

Tom
Posted By: sparky Re: Ground Rod Woes Revisited... - 10/02/02 10:15 PM
Quote
250.56 Resistance of Rod, Pipe, and Plate Electrodes.
A single electrode consisting of a rod, pipe, or plate that does not have a resistance to ground of 25 ohms

Right on Don. 5/8" x 8' contact area simply can't compete...

Quote
(A) Rod, Pipe, and Plate Electrodes. Where practicable, rod, pipe, and plate electrodes shall be embedded below permanent moisture level. Rod, pipe, and plate electrodes shall be free from nonconductive coatings such as paint or enamel.
interesting obsvervation E~Scott, i never really considered this ( so thank you~!)...... [Linked Image]
again appliable to what seems the least efficent
Posted By: pauluk Re: Ground Rod Woes Revisited... - 10/03/02 08:23 PM
Well, the last ground rod I sank took all of two minutes and went in with nothing more than a 2 lb. ball-pein hammer. Still, that was only a 4 ft. rod and the soil here is sandy and largely free of rocks and other impediments!

Virgil,
Have a look here where we discussed testing ground rod resistance using the traditional three-electrode method.
Posted By: Scott35 Re: Ground Rod Woes Revisited... - 10/04/02 06:27 AM
Virgil,

If you do an Encased Electrode [Ufer], here's some specs:

<OL TYPE=1>

[*]At least 20 feet of Encased Conductor,

[*]Depth of at least 24 inches,

[*]Largest Conductor size is 4 AWG cu I believe - verify in Article 250.
</OL>

Suspend the bare Conductor so it will be in the center of the Concrete. This can be done several ways, but one of the simplest is to pour a "Bottom Layer" of Concrete first, place the Conductor on top of it, then pour the "Top Layer" of Concrete.

Good luck!

Scott S.E.T.
Posted By: Sean WB Re: Ground Rod Woes Revisited... - 10/04/02 06:45 AM
I am not sure yet sparky66, Im still waiting for the snail mail from SBCCI [Linked Image]
yeah, the megger I got is used for checking old feeders etc. mostly underground feeders because of the corrosive soil here by the coast. most of them I check fail.. I was fed up with that last barn I worked on and a megger would have saved me lots-o-time. at least I made enough on that job to by a megger [Linked Image] ...
On second thought , maybe I will suggest new underground feeders/services BEFORE I troubleshoot [Linked Image]
Posted By: Nick Re: Ground Rod Woes Revisited... - 10/05/02 04:38 PM
Here are some pictures of a Uffer I recently installed. It has to be near the bottom exterior of the footing. The pictures were for the AHJ incase he didn't show up for the 8:00AM concrete pour. The pour was on a Monday morning and I discussed getting pictures for him the previous week. The job is in a rather shady industrial area and I convinced them that if I installed the copper the previous week for inspection it would disappear over the weekend. Now that is in and we are off site I am expecting to come back and see the tails that go to the gear cut off at the concrete. Maybe I will get lucky.
You probably can't see in the picture but the copper is suspended off the rebar. I got in this habit because of a rebar inspector a while back. He did not like to see our 4/0 copper running with and tied to the rebar. He claimed it displaced concrete. So what I did was hung it off the top straps with tie wire then tied it down to the lower straps to keep it from floating. Keeps everyone happy. Even doing it this way the whole thing takes about 20 minutes to install.

[Linked Image from pstr-m02.ygpweb.aol.com]
[Linked Image from pstr-m02.ygpweb.aol.com]
[Linked Image from pstr-m04.ygpweb.aol.com]
Posted By: Bjarney Re: Ground Rod Woes Revisited... - 10/05/02 11:45 PM
Nick — Aren’t pictures you don’t have to get from the drugstore wonderful? And this crazy internet.
Posted By: tdhorne Re: Ground Rod Woes Revisited... - 10/06/02 04:56 PM
Have any of you had any success getting the rebar stubbed up at the location of your service disconnecting means? Since the rebar itself is acceptable as an electrode why not use it?

On one job I supplied a twenty foot long, half inch, galvanized, rebar and the concrete guys put the 90 and the kick in it and tied it to the top of their stirrups. After the connector sleeve was in place I painted the whole thing with the same black protective coating that is used on rigid conduit threads. I am assuming that it will outlast the building.
--
Tom
Posted By: caselec Re: Ground Rod Woes Revisited... - 10/06/02 05:37 PM
In my area (Northern CA) the foundation contractor usually provides the UFER ground many times without asking them to. They tie 2 additional 20' pieces of rebar (1 in each direction) to their lowest bar in the footing and leave them sticking up above the foundation about 18" near the service panel location.

Curt
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