Chopping the driven ground

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#1

Originally Posted By: kshepard
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Driving an 8 ft. copper rod completely into the ground in the “Rocky” Mountains is often near impossible. I keep talking to EC’s who say they’ll try 3 times, then cut it off. Often at 18". Sometimes they’ll drive a second rod but you just know they have the same problem. Since all you can ever see is the top of the rod anyway, technically the main grounding electrode isn’t ever visible (at least when it’s a driven rod).


Does four 2ft driven rods equal one 8 ft. driven rod? An you'd have to spread them out over 24 ft. Or recommend ground quality confirmation by an EC at every inspection. I'd almost rather do it myself if I had the equipment. What's used? Or is that another can of liability worms?

Kent

#2

Originally Posted By: Jay Moge
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sounds like a little over the sop. even though i’m not a full member i still follow it to a “T”. i mearly note the presence of the rod and that i have no way of telling if it’s deep enough. just like a poured slab, i can’t tell if the soil is compacted enough or if there is a barrier, nor am i going to start carrying a shovel to check. sounds like it’s not cost effective to me. a multimeter can give you a good idea on the resistance of the rod to earth, but still a lot of variables to consider for me to say it’s deep enough. but maybe some one els has a better answer. icon_cool.gif

#3

Originally Posted By: jpope
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Quote:
Rod and pipe electrodes shall not be less than 2.5 m (8 ft) in length. . .


Tell them to try a "Plate Electrode." 250.52(6)

--
Jeff Pope
JPI Home Inspection Service
"At JPI, we'll help you look better"
(661) 212-0738
#4

Originally Posted By: jpope
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Jay Moge wrote:
i have no way of telling if it's deep enough.


Unless they cut it before the drive it, you should be able to see the listing stamp.

--
Jeff Pope
JPI Home Inspection Service
"At JPI, we'll help you look better"
(661) 212-0738
#5

Originally Posted By: Jay Moge
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jpope wrote:
There are other methods that can be used for the GEC. I don't see how "doing it wrong" 4 times, can make it right.

Quote:
Rod and pipe electrodes shall not be less than 2.5 m (8 ft) in length. . .


Tell them to try "Plate Electrode." 250.52(6)


he's right. 4 wrongs don't = right, but 3 lefts = a right. ![icon_cool.gif](upload://oPnLkqdJc33Dyf2uA3TQwRkfhwd.gif)

#6

Originally Posted By: kshepard
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True, I commonly see it both ways when I see it at all.

"Plate Electrode"

Thanks Jeff

#7

Originally Posted By: gbeaumont
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Hi to all,


many people also think that the driven ground has to be vertical, in fact the driven rod can be at an angle, the important issue is the surface area of the rod that is able to dissipate stray current.

Regards

Gerry

--
Gerry Beaumont
NACHI Education Committee
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NACHI phone 484-429-5466

Inspection Depot Education
gbeaumont@inspectiondepot.com

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#8

Originally Posted By: Jay Moge
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kshepard wrote:
Unless they cut it before the drive it, you should be able to see the listing stamp.

True, I commonly see it both ways when I see it at all.

"Plate Electrode"

Thanks Jeff


the lazy apprentice may be inclined to cut the bottom of the 3rd attempted rod to get home befor beer:30. ![icon_cool.gif](upload://oPnLkqdJc33Dyf2uA3TQwRkfhwd.gif)

#9

Originally Posted By: bkelly1
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Here they also accept it horizontal at least 18 inches deep.

–
“Do, or do not. There is no ‘try’.” -Yoda (The empire Strikes Back)

#10

Originally Posted By: kshepard
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In parts of the country where it’s difficult to drive a rod, ufer’s ought to be a good alternative, but I never see them. They ought to be visible in the crawlspace, although often the GEC just disappears down into the wall and it’s not apparent where it goes. Before about 1970 there was a lot of real funky unpermitted building back up in the mountains here.


On new construction why can’t they bury a plate electrode during backfill for a really good ground?


Kent

#11

Originally Posted By: Greg Fretwell
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Ufers are the standard electrode in Florida new construction. It is part of the footer inspection.

#12

Originally Posted By: jmyers
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Gerry,


Not that I am one to disagree, but I am pretty certain (about 95%) that the ground rod can not be driven on less than a 45 degree angle, per the NEC.

BTW....HIYA Gerry LTNS.

--
Joe Myers
A & N Inspections, Inc.
http://anii.biz

#13

Originally Posted By: Thomas Ogryski
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Joseph is correct, a ground rod driven at an angle must be within 45 degrees of vertical.


Also, galvanized ground rods are not required to be listed, so there are no marks stamped on them. Just look for the saw marks on the top of the rod, it is amazing hopw many people don't beat them off with a hammer.

I once did a service inspection and the first thing I noticed was two 2' pieces of ground rod laying on the ground. The homeowner misunderstood the power company handout & put in two six foot rods eight feet apart.

#14

Originally Posted By: bbadger
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kshepard wrote:
In parts of the country where it's difficult to drive a rod, ufer's ought to be a good alternative, but I never see them. They ought to be visible in the crawlspace, although often the GEC just disappears down into the wall and it's not apparent where it goes.


Just how would anyone but Superman 'see' a uffer?

The NEC requirement for a concrete electrode is as follows.

Quote:
250.52(A)(3) Concrete-Encased Electrode. An electrode encased by at least 50 mm (2 in.) of concrete, located within and near the bottom of a concrete foundation or footing that is in direct contact with the earth, consisting of at least 6.0 m (20 ft) of one or more bare or zinc galvanized or other electrically conductive coated steel reinforcing bars or rods of not less than 13 mm (? in.) in diameter, or consisting of at least 6.0 m (20 ft) of bare copper conductor not smaller than 4 AWG. Reinforcing bars shall be permitted to be bonded together by the usual steel tie wires or other effective means.


By the way a small and unimportant point is that we use the term Uffer as slang for a concrete encased electrode.

A "Uffer" is a specific system of concrete electrodes, the NEC does not require a true ufer, the only thing the NEC requires is as described above.

What this means is all uffers are concrete encased electrodes but not all concrete encased electrodes are Uffer systems. ![icon_wink.gif](upload://ssT9V5t45yjlgXqiFRXL04eXtqw.gif)


Quote:
On new construction why can't they bury a plate electrode during backfill for a really good ground?


A concrete encased electrode in the footing is the best connection you are going to get to the earth.

It is almost imposable for it to be compromised and it has the greatest surface area in contact with the earth.

At the voltages used in a dwelling unit grounding electrodes do nothing for faults in the home.

Here are some things that the grounding electrode can help with.

1) Lightning strike on any items bonded to it.

In this case an electrode may help but if the strike is close enough all bets are off.

2)Overvoltage from the utility.

There are few ways that utility company faults can direct high voltages 7,200, 13,800 etc. into your home wiring. This is not a 'Good Thing'. ![icon_wink.gif](upload://ssT9V5t45yjlgXqiFRXL04eXtqw.gif)

For those voltage levels a grounding electrode will help.

I will try to explain.

Imagine you have a grounding electrode with 25 ohms of resistance.

Now have a 120 volt fault into it.

120 / 25 = 4.8 amps.

4.8 amps will not trip a 15 or 20 amp breaker or fuse.

Now imagine a 7,800 volt fault into it.

7,800 / 25 = 312 amps.

312 amps will open the power company's over current protection.

Maybe saving your house from burning down.

--
Bob Badger
Electrical Construction & Maintenance
Moderator at ECN
#15

Originally Posted By: Greg Fretwell
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Bob, Ufer grounds, Florida style do not require superman to inspect. There will be a 4x4 square cover on the wall adjacent to the service panel. Under that cover there will be a piece of #5 rebar that dissapears down the wall, into the footer. Usually there will be a lot of green paint in the hole from the construction so it doesn’t get poured solid when they pour the dowelled cells. Your GEC to electrode connection will be there, typically an acorn.


Part of the footer inspection it to insure that the stubbed up #5 is tied to the steel in the footer. That is two #5s here, lapped and tied all the way around and also lapped and tied to the dowelled cells rebars that get tied to the tie beam that the trusses strap to. Your ground electrode ends up being a virtual Faraday cage from footer to the trusses. It makes RF stuff hard to use tho. icon_wink.gif

#16

Originally Posted By: bbadger
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Greg you can not see the concrete electrode unless you are there before the pour. icon_smile.gif


All your 4" x 4" cover lets you see is the connection.

I still do not agree an HI can see a concrete encased electrode. ![icon_smile.gif](upload://b6iczyK1ETUUqRUc4PAkX83GF2O.gif)

I do not know what they are doing for homes here but we usually stub up a length of 4 AWG to 4/0 copper that will reach the service disconnect.

Bob

--
Bob Badger
Electrical Construction & Maintenance
Moderator at ECN

#17

Originally Posted By: rschuemann
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I know in the Denver area you can call Xcel Energy & they will come out & test the ground.


For an added charge to your next utility bill, of course.

RS

#18

Originally Posted By: Greg Fretwell
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They don’t have much luck with the copper wire idea. It either gets broken accidently or someone is just stealing them.


By stubbing up the #5 they have an attachment point that is mason and/or framer proof.


Just between you and me, it is also something the concrete crew can do. They don't have copper wire or acorns. Electricians may not even be contracted yet when this is installed ... just don't tell the electrical inspector.
The structural inspector checks the Ufer since 250.52(A)(3) says "Reinforcing bars shall be permitted to be bonded together by the usual steel tie wires or other effective means."
The stub up for the Ufer is made up just like the stub ups for the dowelled cells. (a 36" "corner bar" tied to the rebar in the footer) That is why they have to spray it green or the cell it was in would be poured solid.

#19

Originally Posted By: kshepard
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I thought the steel was just stubbed out the top or inside (crawlspace) of the foundation wall (poured or CMU) where it would be accessible for clamping to a copper wire to the panel.


Of course there’s be no way to confirm the connection to other steel in the foundation, but doesn’t the concrete or grouted block act as a ground as well?

#20

Originally Posted By: pabernathy
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Hey Guys,


ON most UFERS or even cased electrodes they simply turn up the rebar at the panel location and if it is done differently then most EC's ( like myself ) will throw quite a FIT and you bet next time it will be turned up at the panel location.

Now.....lets say you have not even BID the job...will they know where to turn it up..maybe not but if it is a contractor you have been working with they will learn as you go and will start to know the best locations for the panel and thus the turn up point.

I have to say....I prefer a good UFER to a Bad UFER anyday...thehehe

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