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#18658 - 12/12/02 10:19 PM 2 ground rods???  
sparkync  Offline
Member
Joined: Oct 2002
Posts: 826
NC
Where did they get the inspiration to start making us drive 2 ground rods??? Just had to do it the first time since code change in my area, and wouldn't you know it, the house is built on granite rock I think. I hit rock about everywhere I started. Finally got them to go down a little at a time... Hardest ground rods I have driven in 31 years and I had to drive 2 of them.. (the hard way with a pole driver and sledge hammer) [Linked Image] What a work out... wonder if it is really necessary??? [Linked Image]


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#18659 - 12/12/02 10:34 PM Re: 2 ground rods???  
HotLine1  Offline


Member
Joined: Apr 2002
Posts: 6,853
Brick, NJ USA
Hey SparkyNC:
250-56 was in the '99 NEC...not to mant people paid attention to it.
It's being enforced in this area now (NJ).

The choices that you have are to provide "documentation" to the AHJ that one rod tests 25 ohms or less...OR drive a second rod. No testing or documentation is required if two rods are driven.

The "tester" is about $2500-$3000 toy, and there is a lot of instructions to read to perform the testing. You could "just" hand a document to the AHJ, but if he requests proof...????. OR last but not least you can drive the second rod!

For what it's worth, my guys use a B&D Hammer Drill to drive the rods. (Macho 4)

John


John

#18660 - 12/12/02 10:46 PM Re: 2 ground rods???  
sparky  Offline
Member
Joined: Oct 2000
Posts: 5,311
everyone feels the need to build on a mountain here*, so the blasters get the biz.

I usually try for a Ufer , if i'm in the 'loop', and rods commonly go in the service lateral ditch...

*there is no 'flat'.....just up & down


#18661 - 12/13/02 07:56 PM Re: 2 ground rods???  
GEC-1  Offline
Member
Joined: Jun 2001
Posts: 32
Covington, Georgia USA
Hey SparkyNC
Here is another way to look this. To prove that you have 25ohms or less to ground, you would have to drive a second rod to get the readings between them. Here in Georgia, we have to drive two rods also. I choose to drive them right below the drip line of the roof. Because of the moisture falling off the roof there, you're more likely to get a better ground for your grounding electrodes ( not to mention that the ground will be softer there too)!
Also, try driving your ground rods at about a 45 degree angle. The NEC will allow up to 45 degrees on your rods. And last, I use a Bosch hammer with a ground rod bit to drive my rods. Not only wil it drive through rocks with ease, but it will also stop the end of the rod from mushrooming... thus allowing you to put your acorn clamp on after the rod is driven. The3 only downfall I have encountered has been the electrical inspector questioning me if I cut the rod off because the end of the rod looks new after I drive it.
Good luck, and I hope this will help you!


#18662 - 12/13/02 09:13 PM Re: 2 ground rods???  
resqcapt19  Offline
Member
Joined: Nov 2000
Posts: 2,148
IL
This is not a new code rule. The 25 ohm rule is in my '78 code book. 250-84.
Don


Don(resqcapt19)

#18663 - 12/13/02 09:20 PM Re: 2 ground rods???  
sparky66wv  Offline
Member
Joined: Nov 2000
Posts: 2,236
West Virginia
Unfortunately, the 2 rod rule wasn't enforced until recently in my area.

When Allegheny Power came into town, services went up in installation price 50 to 100%!

I am NOT complaining!

[Linked Image]


-Virgil
Residential/Commercial Inspector
5 Star Inspections
Member IAEI

#18664 - 12/13/02 10:04 PM Re: 2 ground rods???  
Nick  Offline
Member
Joined: Aug 2001
Posts: 599
Riverside, CA
GEC-1
Every ground rod I have seen lately has listing marks on the top. You can expose this for the inspector to prove you didn’t cut it.


#18665 - 12/13/02 10:54 PM Re: 2 ground rods???  
crlnva  Offline
Junior Member
Joined: Dec 2002
Posts: 5
in va if the incoming water pipe is copper then you only have to drive one ground rod, thats something i always look for before driving ground rods


#18666 - 12/14/02 03:22 AM Re: 2 ground rods???  
Matt M  Offline
Member
Joined: Mar 2001
Posts: 93
Laporte, MN, USA
Crlnva,

Does VA adopt the NEC into law? If so, then you would still be required to drive a second ground rod if one will not provide the 25 ohms or less to ground as specified in section 250.56, regardless whether the waterpipe primary electrode is copper or not.

Because the average electrical contractor doesn't own the special testing equipment required to measure ground resistance, most electricians will just drive the second rod to satisfy the requirement. Matt


#18667 - 12/14/02 04:08 PM Re: 2 ground rods???  
crlnva  Offline
Junior Member
Joined: Dec 2002
Posts: 5
va is still using the 96 code so maybe that is why, all I know is that I have been present for many inspections of service upgrades and the grounding to the water was good enough


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