Trying to improve earth ground.

[Mike]

Been lurking here for a while. I got an HDTV for Christmas, and almost got sucked into the false security of point of use surge protectors. Anyway, I need someone to explain something to me. I have been doing alot of research on surge protection. My plan was to improve my earth ground (my house is 35 years old), and then get a whole house surge protector installed. Luckily, my CATV, Phone, and Power all come in right next to each other. There is a small pipe that comes straight down out of the meter box that contains a bare ground wire. I assumed that this wire went from the meter box to a cold water pipe underneath the house. My plan was to replace the wires coming from the cable grounding block, and the telco box with bare 6 gauge copper wire (which I did), and disconnect the ground wire from the cold water pipe, and attach everything to a new 8' copper grounding rod. Turns out that the wire coming from the meter went underneath the house to the switchbox. There was about 2 feet of slack buried in the ground with a rusted out grounding rod clamp attached to it. There was also a grounding rod there that I hadn't seen before. I'm guessing that at one point the wire was attached to the grounding rod.

Anyway, my question is, is this a typical setup? I know a good bit about "post switchbox" wiring, but not alot about what happens before there. This may very well be the way it's supposed to be, but for some reason, I was thinking there would be two grounding wires.

Since there was no way to slide on a grounding rod clamp, I went back to Lowe's and bought a cold water pipe clamp, and clamped all three wires to the existing ground rod. With ALL that being said, what is the best way to improve my earth ground system? Is this enough? I REALLY want to protect my new electroinics.

One more thing.... The breaker that controls the outlet that the TV is plugged into is not in the main switchbox. For some reason, it is in a smaller switchbox along with the downstairs A/C, outside. I don't know if this affects anything. Thanks in advance!!!!!

- Mike

[buffalobill]

"In a continuous UPS, the computer is always running off of battery power and the battery is continuously being recharged. You could fairly easily build a continuous UPS yourself with a largish battery charger, a battery and a power inverter. The battery charger continuously produces DC power, which the inverter continuously turns back into

120-volt AC power. If the power fails, the battery provides power to the inverter. There is no switch-over time in a continuous UPS. This setup provides a very stable source of power.

Standby UPS systems are far more common for home or small-business use because they tend to cost about half as much as a continuous system. Continuous systems provide extremely clean, stable power, so they tend to be used in server rooms and mission critical applications. " says

[Tom Horne, Electrician]

Mike wrote:

Mike Improving the earth ground is a project for a very well educated and experienced DIYer or a well qualified electrician. The effective grounding electrodes that can be added to your home are a ground ring or stacked driven rods.

Stacked driven rods are easier to install but they require parts that are not readily available. You will need four or five rods and the appropriate rod couplers. These can be special ordered by an electric supply house. You then go to a rental store to rent an electric jack hammer and a ground rod cup. Using the electric hammer you drive the first rod into the earth at least the distance away from the house that the footer is under the ground. If the footer is eight feet down then the rod should be eight feet out from the foundation wall. If you are using threaded rods you drive them with a screw on driving cap so as not to damage the threads. If you are using threadless couplers you apply the first coupler before driving the first rod. After you have driven the first two or three rod sections so that you are twenty to twenty four feet down you measure the resistance to earth of your electrode by using a ground loop impedance tester in urban areas or a fall of potential ground tester in less built up areas. Those meters can be rented from a rental company that specializes in the electrical contracting industry. These are usually found only in larger cities. Larger or specialized electrical contractors would also have them as part of the firms equipment. You keep adding stacked rods until the impedance of the total rod is less that twenty five ohms or less than five ohms if you want the equivalent impedance of a municipal water system. Depending on the soil and substrates this can take from two hours to all day. I have done electrical work that required specification level grounding for over thirty years. I have never seen two parallel rods have a lower resistance than the same two rods stacked by using a rod coupler and I do mean not once. In very rocky soil you will need one inch rods in place of the usual 5/8" ones. Thickly clad copper weld rods are the only type that is likely to maintain its conductivity over time in most soils. Should you strike true rock bottom before reaching the desired impedance you must either resort to paralleled rods or install a ground ring.

A ground ring is a bare copper conductor that encircles the building at a depth of bury of at least 30 inches. To be fully effective it should be buried below the permanent water table. As you can see that is a lot of work. If it must be a ground ring then you will want to use a ditch witch or a similar trenching machine to dig the trench clean around the building. A shorter length of buried conductor might work but you can't test it until it has been back filled and very well tamped preferably with a mechanical tamper. It will take weeks for a ground ring to reach it's lowest impedance so you should plan to go all the way around the home. Bury the ring conductor as deep as the trencher will go rather than settling for the minimum required by code.

[Mike]

I'm beginning to realize that after today. I'm thinking of having an electrician come out and look at everything, measure ground resistance, improve my earth ground, etc. I don't think that it will take too many stacked rods; I live in a wooded neighborhood (everything stays a little damp), and the soil composition is clay. One good thing that came out of all of this is that I realized that my "earth ground" was really 2 feet of slack buried about 6 inches under the ground.

I'm not intimidated by projects like this, I've done some pretty involved DIY stuff before (tile floors, plumbing, etc.), but I want to make sure that it is done right. Overall, I think that it will be a good investment. Like I said before, I live in a wooded neighboorhood that is prone to lightning strikes. I've lost a cable modem and a fax machine in the 2.5 years that I have been here. Another thing that has amazed me is the abundance of misinformation about surge protectors. Tom, no offense to your profession, but do you think that most electricans will do something similar to what you recommended, or just drive a new rod and say it's grounded?

[anoldfart2]

I got a question for you. Assuming a house is grounded to water pipes in a city water system, and an electrical problem developes, which is sending a voltage into the water pipes, but not enough to trip the breaker. Also assuming that the water mains and laterals supplying the homes are all metallic pipe (copper, steel, lead, etc), Can someone in a neighboring house get shocked when they touch their plumbing? I believe most newer houses have plastic laterals, but in the past they used copper and before that, lead. Connected to steel water mains.

Also, if a person has a well with steel casing, is that well casing not the best possible ground anyone could have?

[Bob]

I think that's possible. Years ago I was bench testing a motor in my garage and got a shock. I found nothing wrong with the motor, so I took a brand new motor out of the box and the same thing happened. Turns out that the rear of my old fuse panel was shorting out, causing voltage to be sent through the earth.

[Stubby]

The small UPS systems (350 watts and up) are nice. They are intended to keep your computer running only long enough to shutdown smootly, typically a minute or two. Also, note the batteries in those units only last about 2 years and replacements cost the same a replacing the whole unit.

[David Martel]

Mike,

Electrical Grounding by R. P. O'Riley, Delmar publishing, is pretty good at explaining this stuff. Sounds like the bad clamp at the electrode may have been your problem so measure the resistance of the grounding system now that you have corrected this. You should probably check with the various utilities before you hook their equipment to your ground. And be sure that your ground is not close to your lightning rod ground.

Dave M.

[Tom Horne, Electrician]

No offense taken by me because in this regard my profession needs offending. Most electricians know the code requirements and how to apply them. It is a rare customer who is willing to pay for anything more. Talk to several electricians. If they own a ground impedance tester that is a start.

You said that the Grounding Electrode Conductor (GEC) from the meter can goes to the main panel in your basement. Are you sure about that or does it go to an underground metal water pipe first? In any case the Grounding Electrode Conductor should not run from the meter can to the main panel because when wired like that it is a parallel path for neutral current. Some utility companies require that the ground rod be attached in the meter can while others absolutely forbid the practice. The code allows you to make the connection of a GEC at any point on the neutral between the end of the utility's service drop or lateral and the enclosure of the Service Disconnecting Means. The Service Disconnecting Means is the first switch, breaker, or fuse pull out that will disconnect the power to the building. There can be up to six such devices needed to deenergize a residential service. Best practice is to run a single GEC to the nearest electrode and from there to the next nearest and so on. That makes the point of attachment of the GEC the single grounding point for that electrical service. It is fairly common to find two or more GECs that are attached to the neutral at different points especially were the utility requires a ground rod at the meter or in lightning prone areas were the GEC for the ground rod is often attached at the service head. This is also common practice in situations were the two electrodes are in totally different directions. What should not be done and may be the case in your situation is that the GEC should not run in parallel with any portion of the neutral conductor.

[Tom Horne, Electrician]

A shock to a person in an adjacent home is unlikely because the Grounding Electrode Conductor in that home is attached to the metal underground water pipe and to the neutral of their service. That provides a lower impedance pathway for the neutral current to get back to the transformer. It would take several simultaneous failures for a shock hazard to develop.

A deep drilled well with a metal well casing is indeed an excellent grounding electrode. A municipal water system with it's miles of undergorund metallic piping is often of lower impedance then even a deep driven well's casing.

[Joshua Putnam]

You can mail-order coupled grounding rods, threaded or tapered, from McMaster Carr Industrial Supply,

They'll typically have them to you anywhere in the U.S. within a few days. Not the cheapest hardware supplier, but very reliable, and much easier to deal with than shop droids who say anything that isn't in stock doesn't really exist.

[Bud--]

Why not drive next to the building since you are using multiple rods and will pass the footing? That would reduce the conductor length and put it all in a more protected area. If away from the building can you use shallow burried #4? If aiming for 5 ohms should grounding electrode conductor be full size as for water pipe?

If a single rod is driven next to the building, as is common practice, only about half of the rod faces dirt. If the foundation was wood (insulator) I would think the ground resistance would be double that for a rod in the middle of the yard. For concrete walls is there conduction along the wall that lowers the resistance? Seen any information along these lines?

For a single rod I would think driving through the basement floor (misisng the footing) would give a lower resistance. The rod has earth all the way around, is not in frozen ground part of the year and is lower in the earth and likely nearer wetter soil or ground water. Probably should be 10' to put the required 8' in contact with the earth.

Great description of coupled rods and installation.

bud--

[Thomas D. Horne, FF EMT]

I've always driven them away from the footer and only part of that is electrical. The backfill near the footer often contains a lot of trash that will block or distort the driven rod.

Even at lower resistance the EGC need not be larger than Number two according to the papers that I read so many years ago.

As for driving through the basement floor that works during construction but after that it is usually too difficult to drive them in a basement with ceilings less than twelve feet.

[J Kelly]

The problem with the well casing is the impedance, as Tom alluded to. For a safety ground it is excellent, for lightning protection it can be marginal. Lightning is not a DC current but acts more like RF and a single long grounding conductor can act as an inductor. I always prefer multiple ground rods spaced at least twice the length of the rods apart, and connected with large stranded copper wire. Using bare wire can be helpful, but will also raise the possiblilty of the soil corroding it away over time.

[Bud--]

Voltage drop form a ground rod drops off rapidly away from the rod. A post quited IEEE 142, Recommended Practice for Grounding of Industrial and Commercial Power Systems as 52% of the total ground resistance within 6 inches of the ground rod and 75% of the total ground resistance within 3 ft of the ground rod. Why space the rods 2x, and why base it on length, not fixed distance. Longer rods should drop off as fast with radius. If concerned with long grounding conductor would multiple rods connect back with separate grounding electrode conductors. Any reference to the above or impedance?

bud--

[J Kelly]

All I can say is Polyphaser recommended the 2X length of rod spacing for protecting tower sites from lightning. They say the ground will saturate in a strike if the rods are too close together.