grounding rods oh but why

P bar Y Safety Consultants Alberta Canada

Grounding Rods Oh but Why?

Electrical circuits may be connected to ground (earth) for several reasons. In mains powered equipment, exposed metal parts are

connected to ground to prevent contact with a dangerous voltage if electrical insulation fails. Connections to ground limit

the build-up of static electricity when handling flammable products or when repairing electronic devices.


• If you’re reading this, chances are you have enjoyed the sense of accomplishment that comes from driving an 8-foot long, mostly steel rod into the earth and connecting a ground wire to it. It’s tough work. At the end of the day, you know that your effort was justified because you have installed a system that will protect people from electrical shock, help safeguard expensive electronic equipment, limit neutral-to-ground voltage and satisfy the NEC along the way. There is an increasing awareness in the electrical industry of the benefits of a low-resistance, high-quality grounding system. This article takes a nuts-and-bolts approach to examining one the most commonly installed components: the ground rod.


What is a ground rod?...•

A ground rod is a metal shaft used for grounding. With plastic pipe now being used for water systems these rods are being used for services and other devices to be grounded. These rods are to be driven in the ground at least 8 ft. These rods when made of iron or steel shall be at least 5/8 inches thick. Non ferrous rods should be free of paint or any other non conductive material should be listed and not less than 1/2 inches thick.Most codes call for a ground system of 25 ohms or less. While, as a practical matter, you can't get to zero ohms, you certainly can get to 25 ohms if the ground rods are properly installed. A single electrode consisting of rod, pipe, or plate that does not have a resistance to ground of 25 ohms or less shall be augmented by one additional electrode of any of the types specified above. Where multiple rod, pipe, or plate electrodes are installed to meet these requirements, they shall not be less than 6 feet apart.


Copper• Copper-bonded, galvanized, and stainless steel ground rods are available

in many different sizes. We will not focus on stainless steel rods as their high cost prohibits widespread use. More commonly used are copper-bonded and galvanized steel ground rods. Besides price, what really makes these rods different? Both rods are composed of a steel core with a tensile strength ranging from 58,000 psi for galvanized rods to >90,000 psi for copper-bonded steel rods. From a theoretical standpoint, the higher the tensile strength, the less likely the rod is to “mushroom” or spread when being driven. This is a concern when rods are being coupled or when connections are being made to the top of the rod. Practically speaking, we all know that any ground rod will mushroom if you hit it without using a drive sleeve specifically designed to prevent this. So, the steel used in a copper-bonded rod may give it a slight edge in “driveability,” but not enough to classify it as a superior electrode.


Galvanized ground rods

• Recently, UL-listed galvanized ground rods have shown up in the market. You may have wondered why now and what does this mean? Underwriters Laboratories had never listed galvanized ground rods in the past and there are no listing requirements for galvanized rods in the existing UL 467 Standard, unlike copper-bonded and stainless steel rods which have clear listing requirements. These rods use the higher tensile strength steel found in copper-bonded rods, which is a plus, but we’ve already established that as a minor benefit. These galvanized rods have a smaller diameter than non-UL listed galvanized rods requiring special accessories and different exothermic welding equipment.

• Most importantly, these rods are coated with the same amount of zinc as their non-UL listed cousins (3.9 mils). Since the coating is the same, there is no increase in service life. So what makes them better? It has been suggested that the UL listing will make the inspector’s job easier by allowing them to visually inspect for the UL mark. Inspectors that had trouble qualifying galvanized rods in the past may appreciate this, but I believe this to be a small minority of the dedicated individuals in this profession.


Effective

• Effective earth grounding is essential for grounded AC and DC electrical equipment and distribution systems. Effective grounding provides the level of safety required to protect personnel and equipment from shock and fire hazard. The understanding and evaluation of a facility ground system should be part of any power quality assurance program


Time vs. Nature. Vs. Chemicals

Over time, corrosive soils with high moisturecontent, high salt content, and high temperatures can degrade ground rods andtheir connections. So although the groundsystem when initially installed, had low earthground resistance values, the resistance of thegrounding system can increase if the groundrods are eaten away.


Shake and Bake Values

First, the NEC code (1987, 250-83-3) requires aminimum ground electrode length of 2.5 meters(8.0 feet) to be in contact with soil. But, thereare four variables that affect the ground resistanceof a ground system:1. Length/depth of the ground electrode2. Diameter of the ground electrode3. Number of ground electrodes4 . Ground system design


In the United States• A national standard to improve product quality as well as

dimensional and physical characteristics for users of galvanized ground rods, the National Electrical Manufacturers Association (NEMA), Rosslyn, Va., recently released ANSI/NEMA GR 1-2001, Grounding Rod Electrodes and Ground Rod Electrode Couplings.

• The ANSI-approved standard, which replaces NEMA GR 1-1997, provides information concerning the construction, testing, performance, and manufacture of ground rod electrodes and ground rod electrode couplings. It includes information about materials, construction, and performance of copper bonded, hot-dip galvanized ground rod electrodes.

•


It is not for life

• The main difference between the two rods is the thickness and type of material used to cover the steel core. Galvanized ground rods are coated with zinc to a thickness of 3.9 mils or .0039 inches. Copper-bonded ground rods are coated with copper to a thickness of 10 mils or .010 inches. It is the thickness and type of material coating that primarily determines the rod’s corrosion resistance and service life. In essence, we are comparing zinc to copper and 3.9 mils to 10.0 mils. I think everyone would agree that, regardless of the material, a thicker coating would provide better corrosion protection and, therefore, longer service life.


Think what do I need


It is about this simple


Grounding Eliminates

• limits voltage in a electrical distribution system to definite fixed values

• limits voltage to within insulation ratings• provides a more stable system with a minimum of transient over

voltage and electrical noise• provides a path to ground in fault conditions for quick isolation of

equipment with operation of ground fault protection• provides grounding of all conductive enclosures that may be

touched by personnel, thereby eliminating shock hazards• reduces static electricity that may be generated within facilities• provides protection from large electrical disturbances (such as

lightning) by creating a low resistive path to earth


It Prevents the Incident• No matter the cause of the ground fault, the path of the electricity

does not flow through the circuit as normal. When working properly the electricity is fed through the positive wire into a load, such as an appliance, then it returns to the electrical panel via the neutral wire. When a ground fault happens, the current bypasses the load and if wired correctly pass through to the grounding wire. Because the circuit now has a direct path to the ground, it causes what is known as a short or short circuit. This short in turn causes the circuit to use overflowing power, this extra power consumption then results in the breaker inside your electrical panel to trip shutting off the power to the circuit.

• Because grounding is so terribly important, the connections that connect your electrical panel to the earth must be made using specific connections.


We use them everywhere


Remember

• Often an issue of great confusion, static electricity can cause catastrophic damage if not controlled properly, especially when transferring flammable materials


Size does matter

Length/depth of the ground electrodeOne very effective way of lowering ground resistance is to drive ground electrodes deeper.Soil is not consistent in its resistivity and can be highly unpredictable. It is critical when installing the ground electrode, that it is below the frost line. This is done so that the resistance to ground will not be greatly influenced by the freezing of the surrounding soil.Generally, by doubling the length of the ground electrode you can reduce the resistance level by an additional 40 %. There are occasions where it is physically impossible to drive ground rods deeper—areas that are composed of rock, granite, etc. In these instances, alternative methods including grounding cement are viable.Diameter of the ground electrodeIncreasing the diameter of the ground electrode has very little effect in lowering the resistance. For example, you could double the diameter ofa ground electrode and your resistance would only decrease by 10 %.


You are at risk

Poor grounding not only contributes to unnecessary downtime, but a lack of good grounding is also dangerous and increases the risk of equipment failure.Without an effective grounding system, we could be exposed to the risk of electric shock, not to mention instrumentation errors, harmonic distortion issues, power factor problems and a host of possible intermittent dilemmas. If fault currents have no path to the ground through a properly designed and maintained grounding system, they will find unintended paths that could include people.


Your safety too• Electric current can be described

as the flow of microscopic particles called electrons through wires and electrical appliances. Materials like metal and water through which electric current (electricity) travels easily are called conducting materials or conductors. The body is an excellent conductor, and electric current from any source passing through the body produces electric shock injuries.


It comes with instructionsTo create a proper ground, you need to drive the rod into the ground. Be aware that pounding the top of the rod may make it impossible to fit the coupler and/ or the wire clamp over the top of the rod. Make sure you put the coupler and wire clamp onto the rod before you begin pounding. You can secure the ground wires to the rod after you’ve driven the rod into the ground.The height of the grounding rod, when fully assembled, may make it difficult to pound the top. You might want to stand on a ladder when pounding or you might want to place the coupler onto the bottom rod (flat side into the coupler) and pound the top of the coupler to drive the rod into the ground a little way.Then place the second rod into the coupler (point side into the coupler) and continue driving the assembled rod into the ground as described below. You may simply place the rod, point side down, in the desired location and drive it into the ground until only 4-5 inches (10-12 cm) of the rod remains visible.Or, you may dig a hole about 6” (15 cm) deep and 6“ (15 cm) wide into which you will drive the rod. Place the rod, point side down, in the desired location (inside the hole) and drive it into the ground until only 4-5 inches (10- 12 cm) of the rod remains visible. Attach ground wires to the rod at this point.The advantage of digging the hole is that you may partially fill in the hole once you have attached ground wires to the rod, thus making less of the rod visible above ground. However, you should always leave some portion of the rod visible above ground.


There is a distance used


ATTACHING GROUND WIRES

• To attach ground wires to the rod, strip away 1 inch (3 cm) of insulation, insert

• the wires between the wire clamp and the rod, and secure the wires in place by

• tightening the wire clamp


A rule of thumb


Earth grounding

There are four types of earth ground testingmethods available:• • Soil Resistivity (using stakes)• • Fall-of-Potential (using stakes)• • Selective (using 1 clamp and stakes)• • Stakeless (using 2 clamps only)


Soil resistivity

The formula is as follows:ρ = 2 p A R(ρ = the average soil resistivity to depth A in ohm—cm)p = 3.1416A = the distance between the electrodes in cmR = the measured resistance value in ohms fromthe test instrument


Place it here please

The soil composition, moisture content, and temperature all impact the soil resistivity. Soil is rarely homogenous and the resistivity of the soil will vary geographically and at different soil depths. Moisture content changes seasonally, varies according to the nature of the sub layers of earth, and the depth of the permanent water table. Since soil and water are generally more stable at deeper strata, it is recommended that the ground rods be placed as deep as possible into the earth, at the water table if possible. Also, ground rods should be installed where there is a stable temperature, i.e. below the frost line.


Put it in the groundThe first method. • I call the barbarian method. Please let me explain. • We take ground rod in hand and place it in the location of are picking and then with are free hand we strike it

with a hammer or other blunt instrument. Results? Well usually you never get that ground clamp on. Secondly you probably have several banged up parts all over your upper appendages. And finally you'll get disgusted and saw it off long before you have it deep enough to do any real benefit. This is the hard and wrong method.

The second method. • is simply an improved version of the above where we fashion a covering device such as section of iron pipe

with a cap screw on. And pound it in the same fashion. End result about same as above. The third method. • Now this will get you all wet that I promise you. But here we go. We construct are own piece of machinery

here folks. So get ready to visit your local hardware store. You will need a piece of ¾ inch steel conduit 10 feet long if you doing an 8-foot rod add 3 feet for 12-foot rods. You'll need 1 bronze hose adapter and lastly a garden hose. Now to assemble are parts. You need to have the conduit thread with national standard pipe thread on one end. This is where you screw the bronze adapter on.

• Connect water hose and insert rod in to conduit. Place the unit over where you want the rod and turn on the water. You may want to install a ball cock valve on conduit between bronze adapter and conduit to start and stop water flow. Now you simply what the water rushing out the pipe dig your hole for you. I like this method it is not fast and don't work in rocks. But hey you have the tool left for whom ever May want use it. And they think your pretty darned smart to have made this gizmo.


For me• MOST OF US HAVE OVER THE YEARS SIMPLY POUNDED THE GROUND RODS WE USE

DIRECTLY INTO THE GROUND AND THEN MADE OUR CONNECTIONS. I HAVE LEARNED THAT THIS IS NOT THE BEST WAY TO INSTALL A GOOD GROUND ROD. IN FACT, POUNDING THE GROUND ROD ALL THE WAY IN DAMAGES THE GROUND ROD AND WILL REDUCE THE LIFE OF THE ROD. WHEN YOU POUND IN THE ROD, THE ROCKS IN THE GROUND SCRATCH OFF THE COPPER PLATING EXPOSING THE UNDERLYING STEEL. THE STEEL CORRODES AND THUS YOUR ROD STARTS TO DETERIORATE.

• LOCATION CONSIDERATIONS: CHOOSE A LOCATION AS CLOSE TO THE CONTROLLER AS POSSIBLE. ALSO LOOK FOR ROUTES FOR YOUR GROUND WIRE WHICH WILL BE AS STRAIGHT AS POSSIBLE. KEEP IN MIND THAT ELECTRICITY, LIKE WATER, WILL TRAVEL THROUGH THE PATH OF LEAST RESISTANCE. BENDS, CURVES, AND DISTANCE CHANGE CONDUCTIVE CHARACTORISTICS. IF USING A MULTIPLE ROD CONFIGURATION, AND IF YOU HAVE THE REAL ESTATE TO ACCOMODATE, INSTALL THE RODS 2 TIMES THEIR LENTH FROM EACH OTHER. THE GEOMETRIC SHAPE IS NOT AS IMPORTANT AS THE SPACE BETWEEN THE RODS. IF THE ROD IS 10 FEET LONG, SPACE THE RODS 20 FEET APART EITHER IN A STRAIGHT LINE OR IN A TRIANGLE.


Rod measurements

• The length and diameter of the ground rod not only affect its resistance but also its driving characteristics. Although larger diameter ground rods do not have an appreciably lower ground resistance value, they do have a larger steel core that makes them easier to drive in harder soil by providing extra rigidity. It's probably no coincidence that most rods driven in Canada, with its harder soil, are 3/4 inch in diameter as opposed to 5/8-inch rods which dominate in the United States.

• The length of a ground rod plays a much bigger role in its final ground resistance measurement, and it goes without saying that it takes longer to drive a longer ground rod. The NEC and UL require a ground rod to be at least 8 feet in length. This specification was obviously created by engineers that had never driven a ground rod or noticed that most people are not 8’ tall. Longer rods are more dangerous to install and bow more when being driven. The more a rod bows or shudders, the less efficient the driving process is. Shorter rods are safer and easier to drive. In fact, I would love to see the industry standardize on using two 4-foot rods and a coupler to achieve the required 8 feet total length. Installations would be faster, easier, and safer not to mention that the logistics of transporting and storing a 4-foot rod are much simpler than longer 8- or 10-foot rods.


Not all ground rods are created equal

• Not all ground rods are created equal nor are the techniques used to install them. Installing a grounding system is best-done right the first time as it is every expensive to rework, and failure of the grounding system puts people and expensive electronic equipment jeopardy. Understanding the functions of a grounding system and the characteristics of the various components used to implement it will allow the electrical contractor to make educated buying decisions.


Ground resistance

Another way to lower ground resistance is to use multiple ground electrodes. In this design, more than one electrode is driven into the ground and connected in parallel to lower the resistance. For additional electrodes to be effective, the spacing of additional rods need to be at least equal to the depth of the driven rod. Without proper spacing of the ground electrodes, their spheres of influence will intersect and the resistance will not be lowered.To assist you in installing a ground rod that will meet your specific resistance requirements, you can use the table of ground resistances,below. Remember, this is to only be used as a rule of thumb, because soil is in layers and is rarely homogenous. The resistance valueswill vary greatly.


Assurance of an Incident

However, good grounding isn’t only for safety; it is also used to prevent damage to industrial plants and equipment. A good grounding system will improve the reliability of equipment and reduce the likelihood of damage due to lightning or fault currents.Billions are lost each year in the workplace due to electrical fires. This does not account for related litigation costs and loss of personal and corporate productivity


Last Page the test of your work

• ALWAYS MEASURE AND RECORD THE GROUND RESISTENCE OF YOUR WORK WITH A METER

•Measure electrical ground rod and grid resistance

grounding rods oh but why

Presentations & Public Speaking

galvanized steel ground

stainless steel ground

ground system

galvanized rods

grounding rods

ground voltage

ground earth

stainless steel rods