ground rod configuration

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Old 10-19-07, 12:53 PM
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ground rod configuration

I am installing a new 200 amp service (main breaker). I'm going to use four 8' ground rods because my soil is very poor (gravel & sand), I have plastic water piping, and no other grounding path to use. I want a very good ground system, I'm not just trying to pass code. I was going to install the rods 8' apart in series with one continuous #6 copper wire using appropriate "acorn" nuts. However, I have been getting different "advice" from various folks, including an electrician. Some are telling me I should run two ground wires from the panel in a "V" configuration with 2 rods on each leg of the "V", others have said I should run 4 seperate groundwires from the panel, one to each rod to get the best ground. Which configuration is legal and will give me the best ground?

Also, if the 4 rods in series is the correct way, does it matter if they are in a straight line or make a 90 degree turn? My panel is on the side of the garage and I can run the ground straight out into the yard, run it along the garage and then turn and run in front of my deck, or run it the other direction along the garage and then in front of the garage overhead doors.

Thanks!
 
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Old 10-19-07, 01:15 PM
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how deep is the water table?

If you really want a good ground, sounds like sand may not allow you to reach an acceptably low resistance, even with multiple rods. You might try rods with threaded ends, so you can extend down 16, even 24' down.
There have been used some soil treatments to increase conductivity, if moist dirt to too far away.
 
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Old 10-19-07, 02:56 PM
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the ground rods should all be connected with one continuous conductor.

As telecom guy states, a longer ground rod (I have driven 40 feet rods before) would be your best bet. I tend not to prefer the treatment methods as they can diminish in benefit over time. As well, the affect of the treatment is only as good as the size of the area treated.

What you should do is drive a couple rods and have your electrician freind run an ohm test to check how resistive just two rods are and then go from there. You may be surprised at the consuctivity of the ground in your area. Just don't run the test in wet weather as that will not give you an accurate reflection of how the system will work in dry weather.
 
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Old 10-19-07, 06:20 PM
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Originally Posted by nap View Post
What you should do is drive a couple rods and have your electrician freind run an ohm test to check how resistive just two rods are and then go from there.
Nap, do you know of any electrician who has the $500-$1500 tester to check ground rod resistance? In almost 20 years I have not met one yet.


Mulligan, what are you trying to achieve with these ground rods?
 
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Old 10-19-07, 07:51 PM
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Actually, ya.

Although they aren;t really the electricians but the contractors they work for, most of the electricians I know have access to one.

It is required to test for resistance per some building contract specs.

the inspector in one of the jurisdictions I work in was telling me of an electricians method for determining adequate conductivity. Had something to do with a fuse, a spst switch, a second ground probe, a bit of electricity and ohms law.

btw: that tester is nothing (cost wise) to the cost of an OTDR. I have access to one of those as well.
 
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Old 10-19-07, 08:10 PM
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That's what I meant by electricians. The contractors.
I guess some bigger guys would spring for one.

Most guys just sink two rods and are done with it since that is what code requires.
Maybe guys who do serious grounding like tower installers. I bet they all have them.

IMO there is absolutely NO reason to sink more than two rods in a residence in pretty much ANY case. They serve almost NO purpose anyway.
If anyone thinks they have anything to do with safety and breakers tripping they are way off.
 
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Old 10-19-07, 08:36 PM
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Originally Posted by Speedy Petey View Post

IMO there is absolutely NO reason to sink more than two rods in a residence in pretty much ANY case. They serve almost NO purpose anyway.
If anyone thinks they have anything to do with safety and breakers tripping they are way off.
but they are intended to provide a 0 volt referrence point. I believe that would be included in the safety heading. I did finally find it in the code where that is astated reason for a GE system.

NEC 2005 250.4(A)(1).

250.4 (A)(2) also gives a safety based justification for a grounding system as well.

I do agree that the grounding electrode system does not provide a benefit for the OCPD's and their function.

As to having access to such testers, I work commercial/industrial so requiring a test and verification of a specified reading is more common than in resi. My current job has 22 ground rods used. Actually, it will have 23 when I am done.
 
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Old 10-19-07, 09:47 PM
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Originally Posted by Speedy Petey View Post
Nap, do you know of any electrician who has the $500-$1500 tester to check ground rod resistance? In almost 20 years I have not met one yet.


Mulligan, what are you trying to achieve with these ground rods?
Speedy Petey,

Obviously I want to meet code/pass inspection. But more importantly, I want to protect my electrical system and high value electronics (stereo, tv, computers, etc.) from the numerous power glitches we seem to suffer from the local power company and from possible damage from lightning. We have a lot of lightning storms in my area. Is there a better approach to achieve this protection?

I will be installing a system surge suppressor as well as individual suppressors on my equipment. However, I was under the assumption these (particularly the system surge suppressor) would be basically worthless without a good ground system.

I understand that in the case of ground faults the equipment grounding system is the important player not the earth ground system. But, I was also (maybe mistakenly) under the impression that a good earth grounding system could increase the speed of response of the OCPD's.

I was given information that the resistence to ground could be decreased with each additional rod. However, the idea of adding sections to the rods to get deeper makes a lot of sense. Our groundwater level varies significantly through the year, and with the gravel (porous) soil any rain or surface water rapidly disappears leaving the soil dry.

Thanks for the input!

Mulligan
 
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Old 10-19-07, 10:11 PM
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But, I was also (maybe mistakenly) under the impression that a good earth grounding system could increase the speed of response of the OCPD's.
Reducing the resistance presented to the shunted power will allow it to be redirected easier. (which gets into Ohms law and affects how much power your system is exposed to.)

I was given information that the resistence to ground could be decreased with each additional rod.
true but how much is dependent on how much continuity each rod has to the ground.

A TVSS does nothing for power sags, only increases greater than the voltage limit of the TVSS. A power conditioner would offer better, smoother power.
 
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Old 10-19-07, 10:38 PM
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Originally Posted by nap View Post
Reducing the resistance presented to the shunted power will allow it to be redirected easier. (which gets into Ohms law and affects how much power your system is exposed to.)

true but how much is dependent on how much continuity each rod has to the ground.

A TVSS does nothing for power sags, only increases greater than the voltage limit of the TVSS. A power conditioner would offer better, smoother power.
NAP,

I'm not familiar with power conditioners. How do they work, where are they installed in the system? Do you have any recommendations on specific conditioners? Are they expensive and do they last very long or get toasted like surge suppressors?

Sorry, lots of questions! But I'm intrigued by the idea and would appreciate any additional info you can provide.
 
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Old 10-19-07, 10:45 PM
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Perhaps the single most important part of any electronics protection scheme is a good homeowner's insurance policy with a full replacement clause on all contents. Be sure that this policy covers loss from all perils.
 
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Old 10-20-07, 05:25 AM
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furd may be right.

a power conditioner is a device used to control the voltage to another device. It "cleans up" ypu power. It prevents sags and surges of voltage.

Google "power conditioner" and read to your hearts content. It is more efficient than writing it all here.
 
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Old 10-20-07, 07:09 AM
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it's about lightning

Ground rods, metal water pipes, rebar, ... work to give a ground path for an on-site lightning strike. A secondary purpose is to provide a path for a surge caused by a primary to secondary short in the utility transformer. If either of these events occur, the grounding system might not be enough to save on site electronics (or even receptacles!). The real purpose is to save the building from explosive forces and fire. Just the inductively coupled energy from a close strike could take out electronics, especially those that have sensitive RF circuits (radio/tv). Tall buildings, cell towers, substations can have elaborate grounding systems to give this protection (grids, many ground rods, air electrodes, large bonding conductors). Single ground rods have been known to blow out of the ground, and i've heard of some spec requiring 10' min. from a building to protect the foundation (i think).
But yeah, if you know that your only ground rods are giving you 25 ohms or more of ground resistance, I'd likely work on them a bit more; the code allows this, but doesn't demand it.

25 ohms times 10,000 amps is how much voltage on your washing machine frame?? A lot, and should give you some pause when dealing with mega-energy.

Power conditioners typically are controlled tap transformers, especially useful for places hit with sags and brownouts. They will raise (or lower) the incoming voltage. Not my first choice for transient protection, since the microseconds of energy duration may not be handled by the conditioner. UPS is another story, likely with a better outcome, but more $$ for a given load.
 

Last edited by telecom guy; 10-20-07 at 07:16 AM. Reason: and conditioners
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Old 10-20-07, 09:56 AM
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Power conditioners typically are controlled tap transformers, especially useful for places hit with sags and brownouts.
actually, that is not true. I believe you are reffering to an isolation transformer which is another animal altogether.

A power conditioner does, or any one of value, would also have a surge supression installed. The conditioning portion will deal with the less than catastrophic (but still possibly damaging) surges while the TVSS portion will shunt the catastrophic surges.

as telecom guy states:

ust the inductively coupled energy from a close strike could take out electronics, especially those that have sensitive RF circuits (radio/tv
that is what the conditioning portion will deal with unless the charge is so great it would then be shunted. There are spikes and surges all the time from lightning and such that are not great enough to engage the function of a TVSS so the conditioner will take care of those lower level changes.
 
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Old 10-20-07, 03:21 PM
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more on conditioning

[QUOTE=nap;1245209]actually, that is not true. I believe you are reffering to an isolation transformer which is another animal altogether.

This topic is difficult to cover in just a couple of sentences, but in the interest of conversation, here goes:

A "basic" power conditioner consists of an autotransformer with a few taps, to take care of typically +/- 20% of power fluctuations. So, a brownout of 100 volts gets 'boosted' to ~115v, too much voltage of ~135v gets 'bucked' to maybe 120v. So it goes. There is some detection and switching circuits in them that take some reaction time, thus limiting their useage to "slow" responses. Slow relative to what a UPS can do; a conditioner is maybe a few sine wave cycles response. These kind of conditioners are great for those folks downstream from a major industrial user, that causes power sag. There is no inherent "transient" protection, UNLESS you also combine the conditioner with TVSS/MOV's which many do. So, yeah, many power conditioners do have transient protection with these additional components, the same as what you have in a surge suppressor outlet strip and the like.

There are "not basic" ferroresonant types that ARE fast, there are "isolation" transformers that are useful for the rare and mysterious "noisy" grounds, a discussion in itself. Both are more $$ than the basic autotransformer auto tap device. Check out the Triplite series for a basic device with TVSS builtin.

And then there is the UPS, which quite simply, won't let anything but a clean sinewave of the correct voltage on the output terminals almost no matter what the input is doing, up to and including unplugged, a very nice thing when computers are involved.
 
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Old 10-20-07, 06:59 PM
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yes, this is too large of a topic to get too deep. the problem with the discussion is there is no standard definition of any of the devices we have been speaking of. Some UPS's offer no filtering and some conditioners offer UPS capabilities and there are several technologies for each and all have their weak points. TVSS inclusion can be found in either of the above devices or not.
 
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Old 10-20-07, 10:22 PM
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My Two Cents

My two cents here, from the POV of the End User:

I had been having fluctuations at my house, major flickering of lights even when larger appliances were not kicking on.

Surely I expected to see an amp draw when the fridge or A/C turned on, but random flickering, especially at certain times of the day?

It sure did have me puzzled, then one of my UPS units stopped working. I tore it apart and found a large-ish capacitor melted down!

No problems with circuit breakers tripping or any fuses blown in any sensitive electronic devices... then a few days later, my microwave in the kitchen stopped working properly.

Okay, it was old, get a new one. Had the new one for a short while, same thing happened (not completely dead, but stopped functioning properly.) I had also noted some strange behavior in my other UPS unit that was not explained on the vendor's website support pages.

Something was amiss.

I metered out the circuits on the first floor where these items are located, and there was in all instances, proper voltage and grounding.

Next, I checked the breaker box-- then had a friend who works for the local PoCo come out and check. He said the same thing... all looked hunky-dorey, except for one thing.

What would that be, I wanted to know?

I had suspected lack of a proper ground, and put new copper clamps on the main water pipe in the basement... the old ones were pretty corroded.

When was the service put in? my friend inquired. I told him that the guy I bought the house from said the 150 A service was installed in 1993 by an electrician. I had the paper work to prove it. Surely it was part of the code that this electrician installed grounding rods. Right?

Okay. But do you know he put in grounding rods, or are you assuming he did?

Naturally, I'm assuming. I've been so busy with other home repairs.

We looked. Nope. He did NOT.

The two of us promptly went out and spent a "few" of my dollars on two copper rods, some connectors, etc. We sank those babies just outside the garage wall, connected everything and I waited patiently to observe any changes inside my house.

I never EVER had any more problems with flickering lights... the UPS stopped its very very odd behavior, and there are no more dead microwaves in my house beyond the first two.

I'm recently contemplating what it might take for me to repair the "new" microwave (only 1 year old, but after investigating my 'warranty'-- what a joke-- it would cost me MORE to have it repaired than buying a new one, which I did anyway.) I'm wondering if it would just be a fuse... but without good grounding, why didn't other devices in my house blow a fuse? And why then did the UPS melt a capacitor?

So the moral of my tale is that good grounding goes a long way to helping preserve the 'health' of our sensitive equipment. Granted, I hadn't ever thought to put my microwave on a surge suppressor or UPS, but the UPS units on the four computers in my house DID keep them safe from the same problem that killed two microwaves.

Sounds to me like two very very LONG grounding rods in your sandy area is the best way, eh? My area has great Earth Ground! yummy.
 
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Old 10-21-07, 05:30 AM
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I am suspicious of this story. I think something else had to be done at the same time.
In '93 there HAD to be some sort of ground to pass code. I don't remember the minimums but you needed something.

Does your house have a metal water pipe coming in?

If this is all true then what do your think the ground rods did? I suspect there was a problem on the POCO's end (NOT in your panel or meter pan) that the ground rods put a band-aid fix on.
 
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Old 10-21-07, 05:25 PM
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It's True

I'm sure you're suspicious, but I'm relating exactly what happened.

Yes, there is a metal water pipe entering the house in the front of the foundation.

I suspect that the small grounding wire I cleaned and reclamped wasn't enough for the 150 A service that guy put in in '93. Maybe it was enough for the original (much lower amperage) service installed in 1948! The former owner told me when he bought the house in 1992, the original box was there, with four fuses. Yes, only four circuits in the entire house.

So he hired an electrician to come in and replace the fuse box with a breaker box, up the service to 150, and run separate circuits for the furnace, A/C (to be installed), the washer, the dryer, the microwave and the refrigerator.

But no... no grounding rods. This isn't a story... it's a fact.

If it is a problem stemming from the PoCo side, so be it. They will not act on it. I've called and asked them to come to the pole, check their end, etc. etc. and they always call back a few days later and say everything is fine.

Now that the rods have been in the earth (since May of '07) there has not been any flickering. Once in a while, there will be a slight dimming when the washer kicks on-- that good old amp draw-- but that's it. No more sags, no more odd noises from the UPS units, no more dead microwave ovens.

It's such a pleasure to simply not have to endure the chronic flickering! Besides, no matter what the context, be it in home, in an automobile, in the PoCo distribution grid, in industrial equipment, if there is no symptom, it's damned hard to "fix" something.

As long as my house and its contents are safe and performing as expected, I can't complain. And in fact, when I had complained, it didn't get me anywhere.

Go figure.
 
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Old 10-21-07, 05:49 PM
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So not much changed with the new service. You say it was "not enough" for the 150A service. The size of the service is totally irrelevant. Your load did not change very much. All you did was separate some circuits. Besides, regardless of service size, the largest required GEC (grounding electrode conductor) going to a ground rod only is #6cu. Anything bigger and your simply wasting money.

Your water pipe is your main grounding electrode. YES, it IS an electrode. The rods are simply supplemental. I don't doubt that they were not installed previously.

Your POCO story is nothing I haven't heard or expereinced.
I called in for a lights going up and down, SEVERELY. This is a classic open or compromised neutral situation. Well, it HAD to be on our side the POCO said. The put their fancy load tester on the meter and got no negative results.
Problem continued. Thing is the pole was in the back yard not reachable by bucket truck. Well, after a few more complaints we got a good line crew to show up, guys I knew for years in the field and I explained it to them. One guy goes up the pole and finds the neutral bug loose and arcing. I mean arcing to the point it melted the aluminum bug nut.
Problem solved.


Nothing against you, and I am glad your problem is fixed, but I would bet that the rods did not fix anything. Especially since you already had a much better electrode in use, the water pipe.
Like you say, it's fixed and that's all that matters.
 
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Old 10-21-07, 10:55 PM
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One last chance...

Y'know, SP... what I'm thinking is this:

On August 9th, there were severe t-storms here, which knocked down trees and lines to all the houses at my end of the street in our small neighborhood. It took 3 days for a crew to come out and restore service, since we are basically at the bottom of the food chain in emergency situations.

Anyhow, when they finally did arrive, several guys pulled like mules with an attached cable (put on by a co-worker up in a bucket) until the pole with the connections was almost upright. Then they put some anchors in the ground, set four orange cones around the anchor point, and took off, as it was sunset.

That was August 13th... and the cones are still there, the crews never returned, the lines above DO work, and there were no further repairs at that time. Nor since.

I'm sure that eventually they will get back and repair what is damaged above, but for now, it is the way it is. Once I got power back to the house, all systems "normal" as one might say.

Perhaps when they do show up (maybe in the spring? I'm guessing...) they would then, without knowing it, repair any neutral problems that might be residing up there. The PoCo probably would never send a crew over to look around like the way you described it, or not without me and several of my neighbors throwing a FIT. I'm not sure I can outlast their stone-walling. But if the top of the pole and the connections are scheduled for a repair sometime in the next few months, perhaps whatever else ails the supply will be taken care of.

Funny how the PoCos all sing the same songs, huh? They must send their reps to seminars on how to deal with John Q Public, aka the serfs, in their eyes.

Thanks for your input.
 
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Old 10-22-07, 05:21 AM
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Well here in NY deregulation has had a big (negative) impact.

We couldn't learn from California's mistakes. We had to copy them.
 
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Old 10-23-07, 01:29 AM
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Hey guys, thanks for all the input! I appreciate it. Not being an electrician, and wiring a house for the first time, I didn't know the subject was so deep and contentious. I am glad to hear that 4 ground rods aren't needed. Being that I alread purchased them, I plan to spread them out, sinking the last one on the back side of my garage where I will be mounting a tv ant., internet radio receiver and sat. dish on the garage peak. I will tie it all together with # 6 copper wire. If I don't get the low ohms I need, I will try going deeper. I will also discuss this with my inspector prior to installation. He seems like a reasonable and helpful fellow. I also plan to install a system surge suppressor and some UPS's on specific high dollar equipment.

Montana also suckered for deregulation, and the PoCo for my current residence is a real pain. Amazing how half a town can experience major power glitches (including power slamming off and on 4 or 5 times in less than a minute, as well as occasional power dips) and their response is always "we didn't experience any problems on our end"! Hell no they didn't experience any problems - they didn't have to replace any equipment, computers etc. The PoCo for the house we are building is a rural electric co-op and they seem much easier to deal with. Might have something to do with being directly accountable to their members ya think? The only thing the other outfit is accountable to is their stockholders.

Anyway, thanks again!
 
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