Ground rods for 320 dual lug service

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Hey I beg to differ im only 50.But 32 years in trade makes me feel like 100 :wink: I only wish we were paid by the amount of ladder steps we climbed over the years. :wink:
 
Don't forget the water.

Don't forget the water.

I thought you said you had a water line involved. If the service is overhead I would drive stacked rods using rod couplers until I got lower than twenty five ohms or I hit rock bottom. I use a demolition hammer and a ground rod cup to do that. I then run a Grounding Electrode Conductor (GEC) from the neutral drip loop to the ground rod or rods. I then run a GEC sized for the service conductors from one panel to the water pipe and a GEC tap sized for the other panels supply conductors to the water line GEC. The only reason that I run the ground rod's GEC from the neutral drip loop is I started out in REA territory and it was required there by the local power coop to provide some lightning protection to the service entry conductors. I don't know if that is affective but until I find out it is not it makes sense to me.
--
Tom Horne

"This alternating current stuff is just a fad. It is much too dangerous for general use." Thomas Alva Edison
 
Re: Don't forget the water.

Re: Don't forget the water.

hornetd said:
If the service is overhead I would drive stacked rods using rod couplers until I got lower than twenty five ohms or I hit rock bottom.
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Do you charge by the hour or rod? :shock:
 
don_resqcapt19 said:
Tom,
If the service is overhead I would drive stacked rods using rod couplers until I got lower than twenty five ohms or I hit rock bottom.
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Why?
Don
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In order to provide some lightning protection to the service entry conductors. I did overstate this though. I only drive stacked rods on houses that sit out on larger lots with few mature trees or on ridge lines and knobs. In other words if the overhead conductors seam to be the highest thing around I use the stacked rods to try to get to 25 ohms. Houses that require 320 amp services more often fall into my "exposed to lightning" criteria.
 
Tom,
There is evidence that lighting current only travels a few feet into the ground and then travels horizontally. Longer rods are not any better for this purpose.
Don
 
don_resqcapt19 said:
Tom,
There is evidence that lighting current only travels a few feet into the ground and then travels horizontally. Longer rods are not any better for this purpose.
Don
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Agreed; however, more rods should increase effectiveness, no?
 
don_resqcapt19 said:
Tom,
There is evidence that lighting current only travels a few feet into the ground and then travels horizontally. Longer rods are not any better for this purpose.
Don
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Don
I was not aware of that. Does that mean that for protecting the service entry conductors that two rods would be more effective? I already use flat braided number two for the GEC, which I got some grief about from some inspectors but they were mollified by the UL listing mark on the roll of wire, can you point me at better information on this. I was stacking the rods to get under twenty five ohms because it bugged me that two rods were adequate regardless of the resultant impedance when one rod was acceptable if twenty five ohms or less. That made the second rod seem like wasted effort and materials. I hate doing useless work. If two rods are better for this purpose I'll happily install them.
 
Tom,
The following is from this document. I know that there are other documents that go into more detail, but I couldn't find them.
At the Sandia Research Lab, a U.S. Department of Energy laboratory, scientists studying triggered lightning have documented a constant characteristic. Lightning tends to move horizontally along the earth once it makes contact, as shown above. This research, coupled with ample evidence in nature, clearly indicates that lightning dissipates horizontally. As a result, grounding systems designed with horizontal electrodes are best suited to deal with lightning?s horizontal dissipation characteristics. Vertically oriented grounding systems, for example ground rods, are not as effective for lightning protection.
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Don
 
I can't help but think that if a lightning bolt can travel 100s (1000s?) of feet through the air that the difference of a few 100 ohms of grounding electrode resistance is going to make a bit of difference in the resulting damage from the strike.

When a speeding train hits a Yugo or a full loaded semi the result is very close to the same. The train is hardly slowed and the smaller vehicles are scrap.

I admit that is a very crude analogy but IMO untrained opinion a lighting bolt is just so devastating that a grounding electrode will do little.

If a lighting bolt strikes my overhead service drop near my home my electrical system and the stuff connected to it will be toast good electrode or bad.

wasted effort and materials. I hate doing useless work.
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IMO you are wasting effort and materials when you;

drive stacked rods using rod couplers until I got lower than twenty five ohms or I hit rock bottom. I use a demolition hammer and a ground rod cup to do that. I then run a Grounding Electrode Conductor (GEC) from the neutral drip loop to the ground rod or rods. I then run a GEC sized for the service conductors from one panel to the water pipe and a GEC tap sized for the other panels supply conductors to the water line GEC.
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and

use flat braided number two for the GEC
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That of course is just my opinion.

To each their own, it is wrong to fault anyone for trying to provide the best job possible. :)


Bob
 
I realize this is only an anecdote but I have had one of my REA style service entry arrangements struck by side flash lightning and it performed very well. The only thing that was really crispy was the secondary protector that I had installed in the panel. The protector had vented and converted to an air gap arrestor. The actual thing first struck was the antenna mast for the television aerial. The television survived. I had taken that as some evidence that my technique was at least somewhat effective. Prior to that heavy up the home owner had lost many electronic devices from microwaves to answering machines to lightning induced transients. After that incident I replaced the secondary surge arrestor with a combination Transient Voltage Surge Suppressor that protects his antenna lead, telephone line, and power all in the same unit. I have also stopped similar losses at a youth summer camp by installing better grounding, The soil there is so rocky that all of the added electrodes were horizontal. Those electrodes consisted of #2/0 copper run with all of the new feeders in the bottom of the three to four feet deep trenches used to run the feeders between buildings. The feeders themselves are run in PVC conduit as four wire, single phase, 120/240 volt, lines. I had to lay two regular rods per building in the trenches with the number two in order to satisfy the local inspector. His position was that since the 2/0 did not encircle the building it was not an electrode regardless of it's length. If I had known about this horizontal dissipation stuff I would have run the rods in stub trenches at right angles to the 2/0. In the case of the summer camp the biggest factor may well be the 2/0 between the buildings that bonds all of the building grounds into a single electrode system rather than the actual impedance of the resultant system. The reason I used the 2/0 by the way was that the supply house offered me the wire from the remainder of a very large real at the scrap price when they realized I was trying to buy bare #2 for grounding. I still have a lot of that real left so I'll use it until it is gone. It must have been left over from the ground ring order of some very large commercial job.
 
I`m in the lightning capitol of the country.Last year after returning from OK. I went to make a phone call no phone,then I flipped on the TV Nascar was scheduled no TV after checking the total was 3 TV`S,1 micro,3 phones,2 computers,A brand new stereo.The phone junction box was blown over 75 ft. away and my cable box looked like it had been part of a barn fire.Oh the lightning arrestor survived :shock: The next time I go build a church for charity I guess I`ll just unplug everything and hope for the best :p
 
allenwayne said:
I`m in the lightning capitol of the country.Last year after returning from OK. I went to make a phone call no phone,then I flipped on the TV Nascar was scheduled no TV after checking the total was 3 TV`S,1 micro,3 phones,2 computers,A brand new stereo.The phone junction box was blown over 75 ft. away and my cable box looked like it had been part of a barn fire.Oh the lightning arrestor survived :shock: The next time I go build a church for charity I guess I`ll just unplug everything and hope for the best :p
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I'm sorry for the beating your house took. Would you be willing to share details of your homes grounding?
 
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