A Full Guide To Ground Rods
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A ground rod, also known by the names earth rod and grounding electrode, is an electrode that is installed into the ground to create the path for grounding. It serves as the link between the ground neutral in the electrical system and Earth, intending to reduce the resistance between the two.
A ground rod is an essential component of a proper grounding system. In the event of a fault, an adequate grounding system ensures that there's enough current flow to trip circuit breakers or blow fuses, disconnecting the faulty circuit.
Ground rod is a long, slender metal rod made from a conductive material copper-bonded steel, solid copper, or galvanized steel. In this guide, we will look into the different types of ground rods on the market.
Types of Ground Rods
Copper-bonded steel ground rods
: These are the most commonly used ground rods in many installations. They are made from steel cores coated with copper, which provides a good balance of strength (from the steel) and conductivity (from the copper).
Galvanized steel ground rods
: Made of steel and coated with zinc for corrosion resistance. They are less conductive than copper rods but are more affordable. Use a galvanized steel ground rod in case you have budget constraints.
Solid copper ground rods
: These rods are made entirely of copper. They offer excellent conductivity but are generally softer and more expensive than copper-bonded steel rods. Great for areas with high-corrosion potential and low-resistivity soils.
Stainless steel ground rods
: These are used in special applications where extreme corrosion resistance is needed. Good for coastal areas and industrial settings.
Graphite ground rods
: These are used in specific applications, especially in high-resistivity soils. They are more brittle than metal rods.
Tungsten ground rods
: Used in rare and specific applications due to their cost, these rods offer a unique combination of properties. The applications include high-temperature environments, scientific facilities, nuclear facilities, telecommunications, aerospace, and military.
Chemical electrodes
: These are not traditional 'rods,' but they are tube-shaped devices filled with salts that, when moistened, help improve the soil's conductivity around the electrode. They are used in areas with high soil resistivity.
Ufer grounds (concrete-encased grounding)
: Named after its inventor, Herbert G. Ufer, this isn't a rod but a grounding method involving embedding a grounding conductor in concrete. It's particularly effective in arid regions (drylands) with low natural soil conductivity.
Plate electrodes
: Instead of rods, large conductive plates (often made of copper) can be buried in the ground to serve as grounding electrodes. They are used when soil conditions are not conducive to driving long rods.
Copper vs. Galvanized Steel Ground Rod
Now, let's compare the most popular ground rods: copper and galvanized steel. They are often compared because of how popular they are compared to other types. Here are the main points you should consider when choosing between copper and galvanized steel:
Copper ground rod is more conductive compared to a galvanized steel rod.
Both are resistant to corrosion, but copper ground rod is more resistant. The zinc coating of a galvanized ground rod can corrode in acidic soils.
Galvanized steel ground rods have more strength, so they perform better in challenging installation conditions.
The main advantage of a galvanized ground rod is the cheap cost.
Copper ground rods have a longer lifespan.
Copper ground rods are great for critical installations or where longevity is a priority. Galvanized ground rods are best for applications with budget constraints.
How To Install a Ground Rod?
Installing a ground rod properly is crucial for effective grounding. Here's a step-by-step guide to installing a ground rod:
Safety First: Always make sure to wear appropriate personal protective equipment (PPE) such as safety glasses, gloves, and sturdy footwear. Also, ensure you're not working near live electrical equipment or lines.
Choose the Location
:
Select a spot away from the building foundation, buried utilities, and other potential obstructions.
Ensure the location complies with local electrical codes and regulations.
2.
Prepare the Ground Rod
:
If you're using sectional rods that need to be joined together, assemble them as per the manufacturer's instructions.
Sharpen or taper the end of the rod if it isn't already. This makes it easier to drive into the ground.
Drive the Rod
:
Hold the rod upright at your chosen location.
Using a sledgehammer or a specialized ground rod driver, start driving the rod vertically into the ground. For greater ease and efficiency, especially for deep installations or hard soils, consider using power tools like an electric or pneumatic hammer drill with a ground rod driving attachment.
Keep the rod as vertical as possible while driving. If the rod starts to bend, you can use a tool called a 'ground rod straightener' or withdraw the rod, straighten it, and restart.
Drive the rod until it's flush with or just above the ground surface. Typically, ground rods are 6 to 10 feet long and should be driven almost entirely into the ground, leaving just a few inches exposed.
4. Connect the Ground Wire
:
Use a grounding clamp or connector appropriate for the rod diameter and wire size.
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Attach one end of a thick copper grounding wire (often #6 or larger, but consult local codes) to the rod using the clamp. Make sure the connection is tight and secure.
The other end of this wire will typically connect to the electrical service panel or the device/equipment you're grounding.
5. Inspect and Test
:
Once installed, visually inspect your work to ensure the rod is secure and the wire connection is tight.
For critical applications or as required by local codes, you should also measure the ground rod's resistance to Earth using a ground resistance tester. This ensures that the grounding system will function effectively.
6. Backfill and Finish
:
If you had to dig up a significant amount of soil or if the ground around the rod was disturbed, backfill the area and compact the soil around the rod.
7. Labeling
(if required):
Some jurisdictions or standards require that the grounding point be visibly marked or labeled. If so, place a label or marker indicating a ground rod below.
3.
Important: Always check with local building codes and regulations before installing a ground rod. Some regions may have specific requirements or need permits for such installations. Also, consider using a utility locating service before you dig or drive anything into the ground to avoid damaging buried utilities.
Rules For Ground Rods
Ground rods typically need to be at least 8 feet in length and have a minimum diameter of 5/8 inch, though 1/2 inch rods are acceptable if they are made of steel and copper-coated.
Ground rods should be driven vertically into the ground to a depth of at least 8 feet. If obstructions, like rocks, prevent the rod from being driven vertically to the full depth, it can be driven at a 45-degree angle or buried horizontally in a trench at least 30 inches deep. A 4-foot ground rod is generally not considered sufficient for primary grounding purposes.
The resistance to ground for a single ground rod should ideally be 25 ohms or less. If it's not, a second ground rod is typically required, spaced at least 6 feet apart from the first rod. The two rods are then bonded together with a grounding wire. If you are contemplating using one or two rods, follow this rule.
Ground rods should be placed away from potential damage sources and should not be installed where they might puncture underground utilities.
After installation and before backfilling any trenches, the grounding system should be inspected to ensure compliance with local codes.
NNC offers various types of ground rods.
For years, manufacturers and users alike have struggled with the selection of ground rod electrode coating alternatives, striving to select the most effective alternative that provides the longest service life. This process is a noble goal, as grounding all too often is looked upon as a step-child and once in the ground that is often the last time any thought is given to effectiveness and reliability of the overall grounding electrode system.
Any number of charts, graphs and allied information available offer suggestions in ground rod coating selection but in the most general of terms. Some national studies have arrived at conclusions using an inconclusive basis for coating selection, leading one to select a product without performing any soil analysis. One does have to be extremely careful of the &#;agenda&#; in use of this information when considering this rod coating, for the number of variables involved, in reality, is too pervasive for even the best soils engineer to draw a single conclusion. One of the main reasons for this is that soil conditions often vary widely within a close area to where the soil sample may have been taken, the point of installation. Note that whatever the rod steel core coating is (copper-plating, zinc-coating and stainless in the case of cladding) is there to protect deterioration of the steel core, not for strength or conductive purposes.
Yet how often is soil analysis of the specific site actually employed? The cost is often prohibitive and, instead, general conclusions are made for overall economic purposes. The most common statement is, &#;We have used this type of rod coating for decades, and it seems to work and we are not changing it under my watch.&#; While not always the most technically sound way to arrive at an engineering conclusion, it more often than not is the justification and probably is not too far off target. Moreover, a single soil analysis can often result in opposing views based upon the engineer conducting the analysis.
In reality, the cost of time and/or money to do otherwise is usually not acceptable due to a variety of reasons. There are many electrical and non-electrical components buried in the earth, and one component may cause the other to corrode via an anodic/cathodic cell. Years ago we experienced galvanized screw anchor failures due to copper-coated rods and other materials buried nearby, and we saw the solution as isolating the cell by one of several means.
On the other hand, engineers are now looking at buried steel poles as a means of grounding versus a driven ground rod electrode adjacent to the pole. What about life of the uncoated steel pole with the material at grade level often in the ³16 to ¼ inch thickness range? And the story continues to include buried gas pipe lines, to above ground pipe lines to include the Alaskan Pipeline where corrosion conditions are taken very seriously.
The following table provides a general guide for the selection of zinc-coated steel, copper-coated steel, or solid 304-stainless-steel ground rod electrodes in soil conditions identified by the ground rod resistance measured during site testing. This guide is NOT intended to be conclusive, but a fundamental guideline often used in rod type coating selection.
Ground resistance is only one measurement criteria to be used in the selection of a coating, but it is generally considered one of the prime factors. Soil pH is another critical factor to be considered, as are several other parameters mentioned below in the comment section. These two factors, combined, have been used as an economic, yet technically supported, basis for rod coating selection. This basis is NOT the most thorough technique to follow, but it is supported by many engineers as to an economical approach to addressing what could be a costly effort.
From the the general service guidelines chart, one might conclude that when faced with low resistance soil conditions most rod coatings are subject to more aggressive unfavorable conditions. On the other hand, under higher ground resistance conditions one might conclude that most coating types are acceptable. So let&#;s consider adding another parameter, soil pH.
The most comprehensive selection method to assure the highest degree of confidence in system reliability is to enlist a soils engineer and accurately identify soil characteristics at the exact location where each grounding electrode(s) is to be installed. Anything less is highly subjective and based upon incomplete technical support in the critical area of electrical service to residential, commercial, and industrial or power utility installations. How many installations are ever re-inspected unless faced with an upgrade where then current electrical codes must often be complied with? Moreover, what about changes to the site at a later date including chemical contamination, other buried installed components, and so forth?
Soil pH at or below 4 is particularly harmful to any of the above alternatives. The higher the pH number, the more likely system life reliability will be enhanced, whereas the lower the number, the more critical the soil conditions may be on any ground rod electrode.
pH&#;
<4 trends poorer (acidic)
4 threshold (neutral)
>4 trends better (basic)
From this information, one might conclude that the makeup of the soil from a chemical perspective is very critical, which of course it is. However, using resistivity and pH together will result in what is used in most cases without having the complete site analysis of soil by a qualified firm.
Well-aerated soils with a neutral or slightly basic pH are likely to cause only limited corrosion of a ground rod electrode.
While the above information based upon ground soil resistivity and pH alone does provide a basic guideline; however, other factors that should be considered in a thorough evaluation include
Copper-coated, zinc-coated or solid 304 stainless-steel ground rod electrodes will generally provide a service life of 30&#;40 years (or more) in certain soil conditions, but not all! This statement is further supported by the history of RUS who have used hot-dip galvanized rods since the early s; Investor Owned Utilities have used copper-coated rods for decades; and industrial facilities who have used stainless-steel ground rods for years, each with great success.
Salts are particularly adverse to zinc coatings, and as a result, galvanized ground rods should not be considered when near coastal areas where salts are prevalent. This situation is where common sense comes to play. Some conditions become quite obvious.
Hardness of the coating should also be considered as a factor in rod selection, as should the electromotive-series-of-metals should the coating ever be compromised. By nature, copper-coated rods are more inclined to be vulnerable to surface coating damage during installation, whereas hot-dip galvanized (not electro-plated) coatings are extremely hard and resist most coating damage resulting from being driven into the ground, similar to solid stainless-steel.
While no one method of rod selection may be considered &#;better&#; based upon continually changing soil conditions (moisture, freezing, etc.) this information is intended to offer suggestions on the most effective coating selection based upon what information may be available to the individual responsible for this selection.
Most errors in establishment and interpretation of corrosion protection for copper-coated, zinc-coated or solid stainless steel ground rod electrodes include one or more of the following issues:
So what does all this mean for those who are responsible for a system which will provide equipment protection, system reliability and personal safety? Maybe a headache would be a good place to start. However, every day decisions must be made that have consequences of one sort or another. Often the decision is to remain with what has worked in the past and not make any changes for fear of failure.
But to look forward and incorporate the technical information available today does allow decisions to be made with a degree of confidence. Using soil resistivity and pH does allow a reasonable conclusion to be made. But for one to say that one type of coating is much better than another is pure minutia. And do not overlook the likelihood of coating damage during the driving process in rocky soil as previously mentioned which opens up a completely new concern. That is, in a galvanized ground rod the zinc-coating then &#;sacrifices&#; to protect an exposed steel core; whereas in the copper-coated ground rod, the steel core &#;sacrifices&#; to protect the copper coating! Think about this!
If you are able find a ground rod manufacturer who offers a 30&#;40 year &#;life guarantee in most soil conditions&#; without conducting due-diligence, including all factors involved with corrosion of zinc, steel and/or copper at a particular site, you should be the first one to get that warranty in writing! If you disagree with this, ask an investor-owned utility firm in the domestic US if they have been offered such a warranty, as they would be the entity most interested in receiving such a guarantee due simply to the number of copper-coated and/or zinc-coated ground rod electrodes installed!
Do not be led by sales or marketing influences when the number of variables that need to be considered for a technically sound installation is too pervasive for any one chart or opinion, this one included! A sound engineering soil analysis is the only way to make a technically sound analysis and decision. Anything less is technically unsound and unsubstantiated!
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