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robt65

Feb 24, 2011, 8:31 AM

Post #26 of 31 (1237 views)

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Re: [turnabout] Building Natural Stone Posts for Electric Lamps and Metal Gates

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The NEC Code requires you to space rods at least 6 feet apart [250.53(B)]. This spacing is a minimum — and far from ideal. When using the typical 8-foot or 10-foot ground rod, you get the best results by spacing the rods at least 16 or 20 feet apart, respectively. This is much greater than the Code minimum 6-foot spacing. If the rods are longer they should be further apart. "If you are very concerned about soil resistively you could always install 3 or 4 rods".
Ground rods spaced less than two rod-lengths apart will interfere with each other because their effective resistance areas will overlap. For reference, see IEEE-142 and Soares Book on Grounding. The overlap increases the net resistance of each rod, making the grounding electrode system less effective than if the rods were spaced farther apart.
Grounding rods must be at least 8ft long, 5/8" in diameter, a resistance that does not exceed 25 ohms (NEC 250.56), typically located 2ft away from the house, and driven vertically into the ground. But, if you can't manage to get it vertically down into the ground, while it is permitted to lay a grounding rod horizontally in a trench in the ground at least 2 1/2 ft deep or to drive it in at a 45 degree angle, just as long as there is at least 8ft of length in contact with the soil, I do have what appears to be a different soil depth (but very dry) and a water table could be reached at a depth of 14 to 17 feet, making a good conductivity.

Note that if the resistance is over 25 ohms or there is very dry soil (damp soil will help to lower ground resistance and dissipate the energy better), you may want to put a second grounding rod in. Place it a minimum of 6ft away from the first. It can also be laid horizontally and must be connected with a jumper cable. No less than 6'. There are rods made that have the ends threaded to add length.

I plan on using my grounding system also for a lightning protection system, which I may want to consider for peace of mind, since we do get a lot of electrical storms.

There are also 3/4" x 10' ground rods that are available at some electrical supply companies, but my depth of water table is greater than 10 foot. I do have a shelf that I believe one ten foot rod (21 feet apart) from two 8 foot rods threaded together would reach. I know this will be over the heads of some, but my information comes from the NEC which I certainly trust over some posters idiotic remarks on this forum.
robt65

A distance of 16' or more from each other is optimal for 8' rods. If the rods are longer they should be further apart. Since I am concerned about soil resistively, I will be installing 3 or possibly 4 rods, (threaded two together) given the depth of the local ground water.

Ignorance is bliss isn’t it turnaround or is it turnabout? But maybe you just can’t understand what the cost of replacing an entire household of major electrical appliances (stove, microwave, side by side refrigerator, 3 flat screen televisions, air conditioners or mini splits, telephone system and several computer systems) would cost, not to mention the loss of spoiled foods. Better skip and whistle back to your tent in SMA and reflect on your ignorance.


(This post was edited by robt65 on Feb 24, 2011, 9:01 AM)


robt65

Feb 24, 2011, 8:37 AM

Post #27 of 31 (1233 views)

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Re: [Rolly] Building Natural Stone Posts for Electric Lamps and Metal Gates

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Hi Rolly,

I believe my reply to turnabout (above) will explain my ground situation. The property lays on very dry soil (with little conductivity) over rock shelves. There are a few areas (within reasonable distance from the structure as stated by NEC) that could support driving a double (threaded rod) that would reach our water able; hence the use of three ground rods, one 10 foot 5/8ths rod and to 8 foot threaded together. I am also using my grounding for a lightning protection system as well as general grounding for the household 200 amp electric system. Hope that explains it for you. Any suggestions, Rolly?

robt65


(This post was edited by robt65 on Feb 24, 2011, 9:02 AM)


Bennie García

Feb 24, 2011, 11:50 AM

Post #28 of 31 (1214 views)

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Re: [robt65] Building Natural Stone Posts for Electric Lamps and Metal Gates

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Us idiots increase soil conductivity by filling the hole around the ground rod with rock salt. Most Mexican electricians know and use this method.


turnabout

Feb 24, 2011, 1:44 PM

Post #29 of 31 (1203 views)

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Re: [Bennie García] Building Natural Stone Posts for Electric Lamps and Metal Gates

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Bennie, I have to agree. All signs point to little or no practical building experience here or elsewhere. Overkill is a sure sign of a novice in any trade. It is part of learning. And who ever said to coat forms with vasoline, that sounds like it came from " Family Handyman". And that´s not good.


Moisheh

Feb 24, 2011, 2:22 PM

Post #30 of 31 (1196 views)

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Re: [Rolly] Building Natural Stone Posts for Electric Lamps and Metal Gates

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I do not know who Benni Garcia is but I can tell he is disagreeable. My remark to Robt. stated ( in the Mexican manner). The pyramids in Mexico were not built by Mexicans . They did not exist as a people when the pyramids were built. Nothing superior about my posts or Robterts. There is nothing wrong with building something to a standard. This is rarely done in Mexico. How would you suggest fastening that "orange crap" to an electrical box or panel? Any installation I have seen has them just shoved into the box. I have never seen any recognized standard label on the tubes nor on the reel. There are a lot of building materials in Mexico that do not met the proper Mexican standard and certainly not UL or CSA. To build a structure and then spend days with a 4.5 inch grinder burying that "crap" into the walls is a horrible idea. The electrical boxes are also "crap" As thin as aluminum foil. Much of the PVC water pipe is second class. If you buy Mexican Sch. 40 it is decent. Look around any large structure in Mexico ( Costco, Soriana, etc. ) They use real conduit and have real tradespeople working on those jobs. The housing industry employ albanils that lay 10 blocks an hour, electricians that think the max # of wires in a conduit is limited only by the # you can squeeze into the conduit. They also do not believe in Marettes ( Wire nuts). Prefer to twist and tape. I could go on for hours. Nothing to do with being superior. Everything to do with doing it right. There are world standards for all of these methods and that is what is followed in both Canada and the USA. How many Mexican tradespeople are actually certified by a governing body? How many trades schools for plumbers or bricklayers exist in Mexico? How many trained building inspectors exist in Mexico? Robert wants to do it right as that is his field of expertise. I say : Go for it!

Moisheh


Rolly


Feb 24, 2011, 2:40 PM

Post #31 of 31 (1190 views)

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Re: [Moisheh] Building Natural Stone Posts for Electric Lamps and Metal Gates

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It seems this thread has run its course and everyone has had a say, so let's move on.

Rolly Pirate
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