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ericc

11:29AM | 01/08/01
Member Since: 01/07/01
3 lifetime posts
Bvelectrical
Hi. I am trying to install a grounding rod.
The area near my electrical box is paved in
with concrete. I acquired a 3/4" star drill
and hand drilling hammer, and drilled
through approximately 4" of concrete over the
next few weeks. The bit dropped a few
inches, and I figured that I hit earth. I
then attempted to drive the grounding rod.
A few inches down, it hit an impenetrable
obstruction. The tip (steel) became blunted.
This was almost a foot down, and I went to
work with the star drill again. The barrier
seems to be impenetrable. What should I do?
Use a larger star drill to make a stepped
hole? Request someone to weld an extension
to the drill? Use a carbide tipped or
tungsten drill?

By the way, service entry is overhead. This
may or may not be applicable.

Thanks, Eric

Lawrence

07:26PM | 01/08/01
Member Since: 11/14/00
333 lifetime posts
Depending on where you live, you might have hit a shelf of bedrock. You also just might have hit a large, buried rock. Rock is much harder than concrete, so the same bits will not work on them.

You might need to find an alternative grounding mechanism if it is a shallow shelf of bedrock. COnsult your local electrical inspector, who might be able to give you solutions to localized problems like this one.

ElectrcBil

08:39PM | 01/08/01
Member Since: 07/21/00
77 lifetime posts
How close are you to the house? If you are too close you are probably hitting the footing of the foundation. I would move out at least 10 inches and redrill. Another suggestion is to rent a large hammer drill. They make the job a lot easier and usually have an bit that will hammer the ground rod in with ease. Try looking for a Hilti t-74 or equivilent drill, make sure you get a large enough bit to fit the rod into the hole it makes. Longer bits are also available. You can also drive the rod by using a little water and a large hammer. Pour the water in the hole and work the rod with the hammer a few inches, pull the rod back out and then put a little more water in and then use the hammer again. Continue this until the rod is in.

rpxlpx

04:47AM | 01/09/01
Member Since: 03/13/00
1678 lifetime posts
ElectricBil's got it.
You'll want to get some concrete mix or concrete repair material to fill the first hole.

ericc

09:27AM | 01/11/01
Member Since: 01/07/01
3 lifetime posts
Hi. Thanks for all the helpful suggestions.
There is a tripping hazard if I drill too far
from the house wall, since the grounding wire
will be too long. Also, I spent a lot of
time drilling the initial hole (about 1 foot,
and 4" of actual hard labor). What I was
hoping was that there was nothing very
dangerous to hit. Gas lines are on the
other side of the house, and the sprinkler
comes out a different end. Is it a good idea
to test with a magnet or steel drill?

I think that I will try ElectricBil's
suggestion to get a big power drill and try
to keep drilling. Also, the water suggestion
sounds helpful, since the base foundation may
be pretty hard.

Thanks again,
Eric

codyboy

05:27PM | 01/18/01
Member Since: 01/09/01
15 lifetime posts
Was wondering does the ground rod have to be above ground and the line coming from the box to the rod. Other wise could not one just dig down 6" or more then put line in and run it to the rod driven down to ground level. Also would it be taking a chance drilling into unknown cement, crack footer
or floor to house like ours on a slab footer. We ran our rod over 3' from the house and buried the line. Wrong ?

tdhorne

08:56AM | 10/04/02
Member Since: 09/01/02
31 lifetime posts
quote:
Was wondering does the ground rod have to be above ground and the line coming from the box to the rod. Other wise could not one just dig down 6" or more then put line in and run it to the rod driven down to ground level. Also would it be taking a chance drilling into unknown cement, crack footer
or floor to house like ours on a slab footer. We ran our rod over 3' from the house and buried the line. Wrong ?

You are not only permitted to bury the rod and the grounding electrode conductor that connects it to the service equipment, you have to either bury it or provide protection from physical damage. Most rods are only eight feet long. If it is not driven below ground it does not have the code required length buried. If you use a ten foot rod you could just bury the GEC but why leave the rod sticking up to trip you, damage car tiers, or damage lawn care equipment.

(G) Rod and Pipe Electrodes. The electrode shall be installed such that at least 2.44 m (8 ft) of length is in contact with the soil. It shall be driven to a depth of not less than 2.44 m (8 ft) except that, where rock bottom is encountered, the electrode shall be driven at an oblique angle not to exceed 45 degrees from the vertical or, where rock bottom is encountered at an angle up to 45 degrees, the electrode shall be permitted to be buried in a trench that is at least 750 mm (30 in.) deep. The upper end of the electrode shall be flush with or below ground level unless the aboveground end and the grounding electrode conductor attachment are protected against physical damage as specified in 250.10.
NEC Handbook © Commentary: "All rod and pipe electrodes must have at least 8 ft of length in contact with the soil, regardless of rock bottom. Where rock bottom is encountered, the electrodes must either be driven at not more than a 45 degree angle or buried in a 2&1/2 ft deep trench. Ground clamps used on buried electrodes must be listed for direct earth burial. Ground clamps installed above ground must be protected where subject to physical damage."

250.64 Grounding Electrode Conductor Installation.
Grounding electrode conductors shall be installed as specified in 250.64(A) through (F).
(B) Securing and Protection from Physical Damage. A grounding electrode conductor or its enclosure shall be securely fastened to the surface on which it is carried. A 4 AWG copper or aluminum or larger conductor shall be protected if exposed to severe physical damage. A 6 AWG grounding conductor that is free from exposure to physical damage shall be permitted to be run along the surface of the building construction without metal covering or protection where it is securely fastened to the construction; otherwise, it shall be in rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, electrical metallic tubing, or cable armor. Grounding conductors smaller than 6 AWG shall be in rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, electrical metallic tubing, or cable armor.
--
Tom

harold endean

06:03AM | 10/06/02
Member Since: 08/30/02
23 lifetime posts
You might want to go to the local rental store and rent an electric hammer drill with a ground rod driver attachment. It could save you a lot of time and bruised fingers.
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