USA Ground Rods are the

second key to Lightning

Protection on Oilfield Sites

Underwriters Laboratories (UL) is notifying electricians, regulatory authorities and consumers

that certain ground rods sold at various hardware and home improvement stores bear a

counterfeit UL Mark for the United States.

http://www.rd.usda.gov/files/UEP_LoM_Supplement3_2015.pdf All rods used must be tested

based upon

Hazard: It is unknown if the mechanical properties and dimensional tolerances of the ground

rods are suitable to ensure an adequate ground path. The performance characteristics for

these ground rods are unknown.

Identification: The counterfeit ground rods are marked NEHRING NCC 588. The marking does

not include a UL control number or the word "LISTED".

What you should do: If you suspect a counterfeit ground rod was installed on your premises,

contact a qualified electrician and have it replaced with a UL-LISTED ground rod. If you have

one of these ground rods in your possession that has not been installed, UL recommends that

the counterfeit ground rod be returned to the place of purchase.

Distributed by: Unknown

Photos of the counterfeit ground rod: The counterfeit ground rods are marked with only the

following information:

This information supersedes UL’s previous public notice dated July 16, 2007.

Name of Product: Ground Rod, Catalog Number PWC 588

Units: Unknown quantity

Manufacturer: Unknown

Date of Manufacture: Unknown

Hazard: The products in question have not been evaluated for safety by UL and are not eligible

to bear the UL Mark. The thickness of the copper plating for these ground rods does not

comply with UL requirements. It is unknown whether the mechanical properties and

dimensional tolerances of the ground rods are suitable to ensure an adequate ground path.

Identification: The counterfeit ground rods are marked with the following information:

What You Should Do: If you suspect a counterfeit ground rod was installed on your premises,

contact a qualified electrician and have it replaced with a UL-Listed ground rod. If you have in

your possession a ground rod bearing a counterfeit UL Mark that has not been installed, UL

recommends that the counterfeit ground rod be returned to the place of purchase.

Distributed By: The ground rods are known to be sold at electrical distributors throughout the

United States.

Counterfeit Ground Rod: Photos of the counterfeit ground rods are shown below:

Legitimate Ground Rod: A photo of the legitimate ground rod is shown below:

Consider the inspector who passes a grounding installation in which an unlisted, unmarked

ground rod is used. He can’t know if the rod is the required eight feet in length or if it has the

required coating thickness. Unless he is carrying a micrometer, he can’t really know whether

the rod is the proper diameter. Should an electrical fire be the result of improper grounding,

he could be liable for damages. If there is a death or a serious injury involved, the damages

could be staggering.

By demanding the use of clearly marked listed (UL or CSA) ground rods, the inspector avoids

this potential liability. Listed rods meet all requirements of the code.

Wholesalers also have significant liabilities associated with selling unmarked rods. While most

galvanized and stainless steel ground rods sold today are not marked, if a rod that has no

markings – neither a listing mark nor a manufacturer’s name or symbol – fails to pass

inspection, the installer could demand a refund from the wholesaler. If there is no way to

identify the manufacturer, the wholesaler is stuck with the loss. By the same token, if there is

a fire or electrocution associated with that same rod, with no traceable manufacturer’s

marking, the liability could stop at the wholesaler.

Selling only rods that are clearly marked with the manufacturer’s name or symbol provides

some protection for the wholesaler against this kind of potential product liability.

An unmarked rod protects only the manufacturer. If you’ve ever wondered why every ground

rod isn’t marked, now you know one big reason.

A contractor’s liability is often limited to a year and a day after a job is completed and passes

inspection. Still, it is hard to imagine why anyone would accept 365 days of potentially

catastrophic liability to save a few cents on a ground rod.

Those most at risk are consumers: homeowners and business owners who could literally lose

everything. They play no role in choosing ground rods, but the lives of their families and

companies are in the hands of those who do. Maybe it is just a ground rod to you, but to them

it could be a matter of life and death. Make the responsible choice. Installing and selling only

traceable, listed ground rods is in everybody’s best interest.

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. http://www.neca-

neis.org/

Testing.

The standard three-point fall-of-potential or slope test on a “totally isolated electrode,” as

described in the IEEE Std. 81-1983, will determine the effectiveness of a grounding system.

You can test nearly any site with a standard three-point ground tester. This equipment works

at a safe output of up to 50 mA and — when not affected by on-site stray voltages — provides

accurate values if properly employed. However, people often perform the test without shutting

down power or isolating the grounding system from the utility neutral. Such a mistake will only

provide you with a test of the utility neutral ground.

What Are Ground Rods?

Ground rods are used to connect the grounding system of electrical systems to earth ground.

Ground rods are manufactured of many different materials, although the two most popular are

probably made of copper clad or galvanized steel. These materials are very good conductors

of electricity and allow any dangerous electricty to flow to ground, taking the danger away

from you and the electrical panel.

Ground rods come in both 8' and 10' lengths, however, an 8' ground rod is the common size

used in residential installations. As a rule, ground rods must be a minimum of 8' long, so do

not cut them off! If you are in very dry ground, you may want to consider a special clamp that

allows you to stack ground rods.

Another option is to add a second ground rod, which is a better option, but remember that the

NEC requires them to be a minimum of 6' apart. If possible, try to get the ground rods in a

moist area around your home. Usually, the area close to the exterior wall has enough moisture

due to runoff water from downspouts.

Ground rods come in varying thickness that include 3/8", 1/2", 3/4", and 1". The minimum

diameter ground rod allowed is 3/8".

Although there are many types of wire, including copper and aluminum, copper is the best for

connecting to earth ground. You see, the ground wire, often referred to as the grounding

electrode conductor, is the link between the ground rod and the service ground connection.

Usually a #6 wire is used to make this connection, but a larger wire may be used to make a

bigger connection if you'd like. In larger electrical service installations, a larger ground wire

would be needed.

Grounding clamps are used to connect the grounding electrode conductor to the ground rod.

There are mechanical clamps that have set screws taht tighten the clamp around the ground

rod to form a connection.

An acorn clamp is an oval-shaped clamp with a bolt used to tighten it to the ground rod. An

acorn clamp is the most commonly used clamp for ground rod connections and is approved for

direct burial applications. The grounding conductor should be attached against the ground rod

and in the "v" of the acorn clamp, opposite the bolt side of the clamp.

Driven Rod

The standard driven rod or copper-clad rod consists of an 8 to 10 foot length of steel with a 5

to 10-mil coating of copper. This is by far the most common grounding device used in the field

today. The driven rod has been in use since the earliest days of electricity with a history

dating as far back as Benjamin Franklin.

Driven rods are relatively inexpensive to purchase, however ease of installation is dependent

upon the type of soil and terrain where the rod is to be installed. The steel used in the

manufacture of a standard driven rod tends to be relatively soft. Mushrooming can occur on

both the tip of the rod, as it encounters rocks on its way down, and the end where force is

being applied to drive the rod through the earth. Driving these rods can be extremely labor-

intensive when rocky terrain creates problems as the tips of the rods continue to mushroom.

Often, these rods will hit a rock and actually turn back around on themselves and pop back up

a few feet away from the installation point.

Because driven rods range in length from 8 to 10 feet, a ladder is often required to reach the

top of the rod, which can become a safety issue. Many falls have resulted from personnel

trying to literally ‘whack’ these rods into the earth, while hanging from a ladder, many feet in

the air.

The National Electric Code (NEC) requires that driven rods be a minimum of 8 feet in length

and that 8 feet of length must be in direct contact with the soil. Typically, a shovel is used to

dig down into the ground 18 inches before a driven rod is installed. The most common rods

used by commercial and industrial contractors are 10 ft in length. Many industrial

specifications require this length as a minimum.

A common misconception is that the copper coating on a standard driven rod has been applied

for electrical reasons. While copper is certainly a conductive material, its real purpose on the

rod is to provide corrosion protection for the steel underneath. Many corrosion problems can

occur because copper is not always the best choice in corrosion protection. It should be noted

that galvanized driven rods have been developed to address the corrosion concerns that

copper presents, and in many cases are a better choice for prolonging the life of the grounding

rod and grounding systems. Generally speaking, galvanized rods are a better choice in all but

high salt environments.

An additional drawback of the copper-clad driven rod is that copper and steel are two

dissimilar metals. When an electrical current is imposed, electrolysis will occur. Additionally,

the act of driving the rod into the soil can damage the copper cladding, allowing corrosive

elements in the soil to attack the bared steel and further decrease the life expectancy of the

rod. Environment, aging, temperature and moisture also easily affect driven rods, giving them

a typical life expectancy of five to 15 years in good soil conditions. Driven rods also have a

very small surface area, which is not always conducive to good contact with the soil. This is

especially true in rocky soils, in which the rod will only make contact on the edges of the

surrounding rock.

A good example of this is to imagine a driven rod surrounded by large marbles. Actual contact

between the marbles and the driven rod will be very small. Because of this small surface

contact with the surrounding soil, the rod will increase in resistance-to-ground, lowering the

conductance, and limiting its ability to handle high-current faults.

Advanced Driven Rods

Advanced Driven Rods are specially engineered variations of the standard driven rod, with

several key improvements. Because they present lower physical resistance, advanced rods

can now go into terrain where only large drill-rigs could install before and can quickly be

installed in less demanding environments. The modular design of these rods can reduce

safety-related accidents during installation. Larger surface areas can improve electrical

conductance between the soil and the electrode.

Of particular interest is that Advanced Driven Rods can easily be installed to depths of 20 ft or

more, depending upon soil conditions.

Advanced Driven Rods are typically driven into the ground with a standard drill hammer. This

automation dramatically reduces the time required for installation. The tip of an Advanced

Driven Rod is typically made of carbide and works in a similar manner to a masonry drill bit,

allowing the rod to bore through rock with relative ease. Advanced Driven Rods are modular in

nature and are designed in five foot lengths. They have permanent and irreversible

connections that enable an operator to install them safely, while standing on the ground.

Typically, a shovel is used to dig down into the ground 18 inches before the Advanced Driven

Rod is installed. The Advanced Driven Rod falls into the same category as a driven rod and

satisfies the same codes and regulations.

In the extreme northern and southern climates of the planet, frost-heave is a major concern.

As frost sets in every winter, unsecured objects buried in the earth tend to be pushed up and

out of the ground. Driven grounding rods are particularly susceptible. Anchor plates are

sometimes welded to the bottom of the rods to prevent them from being pushed up and out of

the earth by frost-heave. This however requires that a hole be augured into the earth in order

to get the anchor plate into the ground, which can dramatically increase installation costs.

Advanced Driven Rods do not suffer from frost-heave issues and can be installed easily in

extreme climes.

Grounding Plates

Grounding plates are typically thin copper plates buried in direct contact with the earth. The

National Electric Code requires that ground plates have at least 2 ft2 of surface area exposed

to the surrounding soil. Ferrous materials must be at least .20 inches thick, while non-ferrous

materials (copper) need only be .060 inches thick. Grounding plates are typically placed under

poles or supplementing counterpoises.

As shown, grounding plates should be buried at least 30 inches below grade level. While the

surface area of grounding plates is greatly increased over that of a driven rod, the zone of

influence is relatively small as shown in “B”. The zone of influence of a grounding plate can be

as small as 17 inches. This ultra-small zone of influence typically causes grounding plates to

have a higher resistance reading than other electrodes of similar mass. Similar environmental

conditions that lead to the failure of the driven rod also plague the grounding plate, such as

corrosion, aging, temperature, and moisture.

Ufer Ground or Concrete Encased Electrodes

Originally, Ufer grounds were copper electrodes encased in the concrete surrounding

ammunition bunkers. In today’s terminology, Ufer grounds consist of any concrete-encased

electrode, such as the rebar in a building foundation, when used for grounding, or a wire or

wire mesh in concrete.

Concrete Encased Electrode

The National Electric Code requires that Concrete Encased Electrodes use a minimum No. 4

AWG copper wire at least 20 feet in length and encased in at least 2 inches of concrete. The

advantages of concrete encased electrodes are that they dramatically increase the surface

area and degree of contact with the surrounding soil. However, the zone of influence is not

increased, therefore the resistance to ground is typically only slightly lower than the wire

would be without the concrete.

Concrete encased electrodes also have some significant disadvantages. When an electrical

fault occurs, the electric current must flow through the concrete into the earth. Concrete, by

nature retains a lot of water, which rises in temperature as the electricity flows through the

concrete. If the extent of the electrode is not sufficiently great for the total current flowing,

the boiling point of the water may be reached, resulting in an explosive conversion of water

into steam. Many concrete encased electrodes have been destroyed after receiving relatively

small electrical faults. Once the concrete cracks apart and falls away from the conductor, the

concrete pieces act as a shield preventing the copper wire from contacting the surrounding

soil, resulting in a dramatic increase in the resistance-to-ground of the electrode.

There are many new products available on the market designed to improve concrete encased

electrodes. The most common are modified concrete products that incorporate conductive

materials into the cement mix, usually carbon. The advantage of these products is that they

are fairly effective in reducing the resistivity of the concrete, thus lowering the resistance-to-

ground of the electrode encased. The most significant improvement of these new products is

in reducing heat buildup in the concrete during fault conditions, which can lower the chances

that steam will destroy the concrete encased electrode. However some disadvantages are

still evident. Again, these products do not increase the zone-of-influence and as such the

resistance-to-ground of the concrete encased electrode is only slightly better than what a

bare copper wire or driven rod would be in the ground. Also a primary concern regarding

enhanced grounding concretes is the use of carbon in the mix. Carbon and copper are of

different nobilities and will sacrificially corrode each other over time. Many of these products

claim to have buffer materials designed to reduce the accelerated corrosion of the copper

caused by the addition of carbon into the mix. However, few independent long-term studies

are being conducted to test these claims.

Electrolytic Electrode

The electrolytic electrode was specifically engineered to eliminate the drawbacks of other

grounding electrodes. This active grounding electrode consists of a hollow copper shaft filled

with natural earth salts and desiccants whose hygroscopic nature draws moisture from the

air. The moisture mixes with the salts to form an electrolytic solution that continuously seeps

into the surrounding backfill material, keeping it moist and high in ionic content.

The electrolytic electrode is installed into an augured hole and backfilled with a special highly

conductive product. This specialty product should protect the electrode from corrosion and

improve its conductivity. The electrolytic solution and the special backfill material work

together to provide a solid connection between the electrode and the surrounding soil that is

free from the effects of temperature, environment, and corrosion. This active electrode is the

only grounding electrode that improves with age. All other electrode types will have a rapidly

increasing resistance-to-ground as the season’s change and the years pass. The drawbacks to

these electrodes are the cost of installation and the cost of the electrode itself.

Earth-Electrode Comparison Chart

The following chart compares the various types of electrodes versus some important

characteristics that may prove helpful in selecting proper electrode usage.

Driven

Rod

Advanced

Driven

Rod

Grounding

Plate

Concrete

Encased

Electrode

Building

Foundation Water Pipe

Electrolytic

Electrode

Resistance-

to-Ground

(RTG)

Poor Average Poor Average Above

Average

Poor to

Excellent** Excellent

Corrosion

Resistance Poor Good Poor Good * Good * Varies High

Increase in

RTG in Cold

Weather

Highly

Affected

Slightly

Affected

Highly

Affected

Slightly

Affected

Slightly

Affected

Minimally

Affected

Minimally

Affected

Increase in

RTG over

Time

RTG

Worsens

RTG

typically

unaffected

RTG

Increases

RTG

typically

unaffected

RTG

typically

unaffected

RTG

typically

unaffected

RTG

Improves

Electrode

Ampacity Poor Average Average Average *

Above

Average *

Poor to

Excellent** Excellent

Installation

Cost Average Excellent

Below

Average

Below

Average Average Average Poor

Life

Expectancy

Poor

5–10

years

Average

15–20

years

Poor

5-10

years

Average *

15-20

years

Above

Average *

20-30

years

Below

Average*

10-15

years

Excellent

30-50 years

* High-current discharges can damage foundations when water in the concrete is rapidly

converted into steam.

** When part of extensive, bare, metallic, electrically continuous water system.

USA Codes and Enforcement

This publication covers state safety requirements for electrical construction. Most states

adopt by reference the National Electrical Code (ANSI/NFPA standard 70), sometimes with

local changes. Some also adopt by reference the National Electrical Safety Code (ANSI/IEEE

standard C2). Many states with statewide electrical codes allow local jurisdictions to adopt

more stringent requirements. Some states have no electrical codes or enforcement authority,

leaving these matters entirely to local jurisdictions.

Contractor/Electrician Licensing

States with statewide licensing requirements generally have an electrical or licensing Board

with the power to give examinations and issue licenses, and to suspend and revoke licenses

for cause. Some states have no statewide licensing requirements, leaving this matter entirely

to local jurisdictions. Some states have reciprocity arrangements for contractor/electrician

licensing with others that have the same or similar requirements. These are generally

neighboring states.

Exceptions: Some states exempt certain types of work or classes of installations from

electrical code, inspection, and/or licensing requirements. Typical exemptions are listed

below; they are referenced by code letter in the individual state listings:

1.Electric utility installations and wiring, up to and including meters on customer premises.

2.Communications systems including radio, cable television, telecommunications, and similar

systems.

3.Industrial installations.

4.Installations of a specialized nature such as mines, refineries, gas and oil fields, and

transportation systems.

Considerations for Grounding Grid Effectiveness

Use wire at least as large as specified in NEC table 250.94.

Before energizing, perform a continuity test between the grid and the neutral ground

connection.

The ground grid wire must be mechanically continuous to the neutral ground bus.

The ground grid connection may not have any sharp bends in it.

Texas

Code

The 2008 NEC (implemented September 1st, 2008) will be the effective "minimum standard"

for all electrical installations in Texas that is covered by the Act. In addition, all examinations

for state electrical licenses offered on or after that date will be based on the 2008 NEC.

Enforcement

Contractors must have a Texas State Electrical License to perform electrical installations.

Texas Department of Licensing and Regulations - Fort Worth

1501 Circle Drive, Suite 215

Ft. Worth, TX 76119

(817) 321-8350

(817) 321-8365 fax

Texas Department of Licensing and Regulations - Houston

5425 Polk Avenue, Suite G40

Houston, TX 77023

(713) 924-6300

(713) 921-3106 fax

www.tdlr.state.tx.us

You will need one auxiliary potential probe (P2) and one auxiliary current probe (C2) to

perform a three-point test. Connect the C1 and P1 either directly or internally through the

meter to the electrode under test. To perform a valid test, place the C2 probe 100 ft from the

potential probe. If the system under test is larger than one or two 10-ft electrodes, you must

determine the width and length of the system as well as the diagonal dimension. Place the C2

probe at least three times the length of the diagonal from the system under test. For example,

if the system is 30 ft by 40 ft, the diagonal will be 50 ft. You should place the C2 probe a

minimum of 150 ft (3 ft × 50 ft) from the system under test. If the P2 values remain within 5%

to 10% of each other at 52% (52 ft), 62%

(62 ft) and 72% (72 ft) distances, you can

assume the results are accurate. Use the

62% reading as your base value.

To get an accurate test, place the

auxiliary probes on opposite sides of the

electrode under test and take the

average of the readings. If the test values

differ greatly, rotate the position of the

probes 90° around the electrode and take

two more tests. Now average the four

results. Keep in mind, dry conditions or highly resistant soils can make it difficult to get

consistent readings. Adding salted water around the test probes or employing deeper test

probes may be necessary. If stray voltages affect your readings, running a test 90° from the

first test should cancel out these objectionable currents. It may be necessary to use a tester

that provides adjustable or variable test currents.

An alternative to this kind of testing is the clamp-on ground tester, which is effective in many

grounding situations and doesn't require you to turn off the power — nor does its effectiveness

depend on how well you lay out your probes. However, the instrument is useful only if you

follow the instructions that come with the

tester. Doing so will yield a valid test or

will render an indication the test is invalid

— usually, a reading of 0.7 ohms.

When used properly, the clamp-on gives

consistent readings and is an excellent

tool for periodic checking of an existing

system against baseline readings. If you

are reading anything less than a few ohms,

you're probably reading a ground loop. In

that case, you need to look at the system

and make sure you're at the right point.

Don't overlook the three-point test during

new construction either — you may never

get another opportunity to conduct that particular test.

The National Electrical Code requirement in Sec. 250-54, which requires the resistance to

ground of a single-made electrode (e.g., ground rod) to be 25 ohms or less. Unfortunately, it

seems many electrical professionals don't actually test the grounding electrode system (GES)

to ensure they're meeting this requirement. Even fewer of you feel testing the earth ground

system is worthwhile. From a power quality perspective, you may be right.

A GES provides:

• A zero-volt reference for the supplied or derived power systems.

• A path to dissipate lightning or fault current (for higher voltage systems).

• A path for the dissipation of electrostatic currents.

A GES consists of two components: the grounding electrode conductor (GEC) and the

grounding electrode.

You can choose a bare or insulated GEC (sized per Table 250-66) in copper or aluminum. The

GEC connects the grounding electrode to the grounded circuit conductor, the equipment-

grounding conductor, or both, at the main service equipment or the source of a separately

derived system.

The most common types of grounding electrodes (identified by Sec. 250-50 and 250-52) are:

• Structural steel

• Metal underground water pipe

• Ground ring

• Ground rods

How to test. You should measure the resistance of an electrode with respect to the

surrounding soil in the area. You can only do this by using the fall-of-potential method with a

three-terminal, earth ground resistance tester. To properly test the resistance of a GES, you

must follow some simple rules:

1. Disconnect the electrode under test from the rest of the electrical system. Considering this,

it is not possible to test the grounding electrode system in nearly all circumstances.

2. Don't use a meter that injects DC current into the ground rod. Do not use standard VOMs.

3. Don't perform test measurements if the current on a GES is greater than 5A.

Contrary to popular belief, clamp-on earth ground resistance testers can be inaccurate in field

applications. These testers require a low-resistance feedback loop with adequate spacing

between electrode systems to provide meaningful readings. Many people often add a high

resistance (caused by loose connections in the feedback loop) to the displayed value of the

meter. Also, inadequate spacing between electrodes results in the meter only making a

comparative bonding test, which almost always results in a low-resistance value.

Why do I need to reach 25 ohms? The most credible answer to this question is: 25 ohms is a

reasonable value to strive for, given the average soil resistivity for most regions of the United

States. Keep in mind, however, that 25 ohms is not a requirement when you install multiple

electrodes. This is only a requirement for single-made electrodes, per Sec. 250-56. If you drive

the first rod and get a resistance reading greater than 25 ohms, the NEC allows you to drive an

additional rod 6 ft away from the first rod.

Let's say, for example, you drive a ground rod into the soil, but instead of testing that rod to

see if it meets the 25-ohm criteria you drive the second. Once the two rods bond together,

consider the GES complete. But if you don't take a measurement, how do you know your

installation meets Code?

Reality check. In most commercial and industrial low-voltage power systems, technicians do

not perform earth ground resistance testing. But this shouldn't surprise you. An informal poll

of 50 electricians found only four performed earth ground testing in the past. The reasons

cited for not testing were:

• The testers were too expensive.

• The test was too confusing and took too much time.

• Two rods are good enough (most common response).

Impact of power quality. Believe it or not, nearly all electronic equipment will operate properly

without the benefit of a low-resistance GES. Power quality site surveys have shown that in

situations where the grounding electrode resistance is between 5 ohms and 105 ohms, it

doesn't affect equipment.

Galvanized ground rods

The NEC establishes the minimum requirements considered necessary for safety. Most

industrial installations go over and above what the Code requires, since performance and

safety is usually more important than the overall costs.

While process units typically don’t have a complete copper grid like that installed at high-

voltage substations (see IEEE Std. 80), they are concerned about touch and step potentials

during large faults or lightning strikes. Also, during maintenance inspections, the inspector

can visually see that each piece of equipment has a grounding conductor attached to it and

doesn’t have to be concerned if the equipment is adequately grounded. Each tap to equipment

above ground can also be used to test the grounding system to ensure it is intact and

functional.

Copper plating is corrosion resistance. Copper, silver, mercury and gold have high resistance

to corrosion, while processed metals like aluminum and magnesium are easily corroded. Noble

metals like copper become the cathode when joined together with less noble metals in the

presence of an electrolyte (water). Less noble metals become the sacrificial anode and

corrode away.

Not listed in the galvanic table of metals is Graphite, since it is not a metal. Graphite is even

more noble than silver and certainly much nobler than copper. Therefore, if a graphite backfill

material is to be used as a ground “enhancer” to surround copper, the copper will be

sacrificial to the graphite and will dissolve away into the soil.

The following affect the amount and speed of corrosion both above and below the soil:

1. Water. The presence of water mixed with contaminants is the basis of galvanic

corrosion. Pure rain water is slightly acidic (pH 5.5 to 6.0). It picks up carbon dioxide

as it falls which creates carbonic acid. It can start attacking some metals, even

copper, without being in a junction. The ions etched from the copper go into solution in

the rain water. As this rain water drips on galvanized tower sections, it will cause the

zinc to combine and wash off. This leaves the bare steel to oxidize away.

2. Oxygen. This is the main corrosion accelerator. Rain water also picks up oxygen as it

falls through the atmosphere. Water provides an excellent carrier of oxygen.

3. Temperature. Generally, the higher the temperature the faster the chemical reaction.

4. Texture of the metal(s). Glass smooth surfaces are less likely to corrode than rough

finishes.

5. Hydrogen Sulfide. A gaseous product of exhaust emissions, it combines with rain water

creating acid rain. Chlorine. Tap water can have an acidic effect on underground

materials.

6. Inert gases. Helium displaces oxygen and reduces the corrosive effect.

7. Alkaline. Although some alkalis tend to increase the rate of carbon dioxide absorption

from the air, which creates corrosive carbonate solutions, slight amounts of alkalinity

can reduce corrosion rates.

8. Salts. Sodium chloride, found just about everywhere, increases the soil conductivity

and also Why Steel Ground Rods are Copper Plated Document ID: PEN1008

9. Salts. Sodium chloride, found just about everywhere, increases the soil conductivity

and also increases the corrosion process in nearly the same proportion to its

concentration. Other naturally occurring salts or non natural added salts do the same.

Only sodium carbonate or phosphate and potassium ferricyanide form a protective film

that prevents further corrosion.

10. Microorganisms. Both bacteria and fungus can deteriorate metal. Some will give off

acids in trapped water or when they die and decompose into acids.

Types of Corrosion

There are several types of corrosion. Listed below are the common names given for

descriptive purposes:

1. Uniform Etch: A direct chemical attack from salts, urine and acids. If allowed to

continue, a polished surface will dull and then take on a rough or frosted appearance.

2. Pitting: Tiny pin holes from localized chemical or galvanic attack.

3. Inter-granular: Usually galvanic, this is a selective attack along the grain boundaries of

an alloy metal. We have referenced this as “de-alloying.” Typical corrosion-resistant

alloys can break down when corrosion actually works on the individual components of

the alloy.

4. Exfoliation: Found on extruded metals, the corrosion occurs just below the metal

surface and causes a blister to form. This appears where the extruding dyes have

forced the crystal structure of the metal to change direction.

5. Galvanic: The classic two dissimilar metal connection with a water electrolyte bridge

is the most basic of corrosion problems.

6. Concentration Cell: As the amount of oxygen reaching the electrolyte varies, the rate

of corrosion will vary accordingly. High concentrated areas of oxygen will have high

levels of corrosion.

7. Stress: More corrosion will occur where high tensile stress is applied. This is where

metal is bent or where rivets have been driven. Metals that have been cold worked

(bent back and forth several times) should be annealed (stress relieved by heating).

Stress corrosion appears as a crack running parallel to the metal grain.

8. Fatigue: Another form of stress corrosion where pits are defined along the grain.

Additional stress begins to concentrate around them and cracking occurs at the

bottom of the pits.

9. Filiform: Thread-like filament corrosion occurring under painted surfaces where water

and oxygen have penetrated and form a corrosion concentration cell. Why Steel Ground

Rods are Copper Plated.

Helpful Hints

• Mother Nature will see that nothing we place in the soil will last forever. But we can do

our part to design a grounding system that lasts.

• Use all similar metals in your grounding system. If copper is used, don’t mix in tin

plated copper wire.

• On mechanical compression joints, copper joint compound should be used to cover the

hardware. This will prevent corrosion that can cause a loss of compression strength

and increase joint resistance over time. The joint compound, a petroleum based

product with conductive copper flakes, displaces water, oxygen, acids and salts.

• Exothermic connections should be allowed to cool slowly to prevent stress corrosion.

• A grounding system should be tested annually.

• Grounding systems should also be checked annually for corrosion.

• Know your soil’s pH. If acidic, either correct it to neutral or suffer the consequences.

There is one caveat though. When installing large amounts of copper in contact with the earth,

a cathodic protection study should be performed. Copper will act as a cathode and any anodic

material in the earth in the vicinity of the copper, such as iron or steel, will sacrifice itself to

the copper because a corrosion cell could be formed. Underground piping/rebar may need to

have a cathodic protection system installed to protect it from the copper.

The NEC code specifies that a solid copper wire used to connect to a ground rod must be #6

gauge, or larger. It doesn't specify a limit as to the maximum length. Of course, shorter is

better.

The grounding system serves a few different purposes:

1. Make the voltage of the land around your business be at approximately the same voltage

as your power line neutral. This means that you can't shock yourself by holding an

appliance in one hand and touching the earth with your feet.

2. A fault path during lightning storms. When lightning strikes near your business, it

energizes your electrical lines. Surge suppressors will try to shunt the voltage to the

neutral or ground line. Having a good ground will maximize the power transfer out of your

business.

3. Safety. If the neutral going to your business is disconnected and you don't have a ground

to neutral bond in your main panel, both prongs of each electric outlet in your business

will have the full line voltage on it. Older appliances will connect their chassis to neutral,

causing their chassis to hold 120V. With the grounding system properly connected, the

ground will pull the neutral closer to 0 V, reducing the risk of shock.

So, what resistance to ground should you want? The smaller, the better. The electrical code

states that with one ground rod, it must have a maximum resistance of 25 ohms to the earth.

According to a Fluke brochure, you should try to have a ground to earth resistance of less than

25 ohms, or less than 5 ohms for sensitive electrical equipment.

#6 gauge solid copper is approx 0.4 ohm/thousand feet, so having a run of thirty feet will add

minimal extra resistance (about 0.008 ohm). But, it will somewhat reduce the effectiveness of

your system during a lightning storm. For the best lightning protection, your grounding wires

should not have any sharp bends. This is because lightning is a very high frequency signal, and

the wire's impedance increases with frequency. The 0.4 ohm/thousand feet figure is only valid

at DC (zero frequency). While sharp bends do not increase the DC resistance, it does increase

the high frequency impedance.

There are many other rules that I have not mentioned (read the NEC book (NFPA 70) or your

local code for details). As always, use caution when working around electrical systems.

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.

One of the industries leaders Mr. Johnson noted

A lightning strike to an unprotected structure can be catastrophic. One bolt can pack up to

100 million volts of electricity. Imagine that kind of current traveling through business

circuitry. The National Lightning Safety Institute estimates there are roughly 15 to 20 million

ground strikes per year with a higher ratio in areas where soil resistivity is greater.

A path of least resistance

Damage from lightning strikes to residences and businesses can be reduced with the

installation of a lightning protection system. Systems are designed to control or provide a

designated path for the lightning current to travel to ground, with the purpose of minimizing

the risk of fire or explosion within nonconductive parts of the structure.

Most lightning protection systems are made up of several components, including air terminals

(lightning rods), conductors, and surge arrestors and suppressors. Regardless of the type of

system, all must link to some type of ground terminals, usually in the form of metal rods driven

into the earth.

While grounding is not exclusively intended to prevent lightning damage, it can help ensure

electrical safety with its ability to provide reliable electrical connection to the earth. Homes

that meet the current National Electrical Code (NEC) typically have a grounding-electrode

system connected to their electrical service, and these homes are typically equipped with an

electrical distribution system, which includes grounded outlets.

Commercially, good grounding is essential for the power quality of electrical equipment and

distribution systems. The IEEE Emerald Book provides additional guidelines for grounding

electronic and electrical equipment. Some utility companies develop substation grounding

grids to provide electrical protection for items such as power transformers.

Equal ground

Grounding rods can vary from sophisticated electrolytic rod systems with active soil moisture

replenishment to metal-coated steel rods. In addition to the copper-clad and stainless-steel

ground-rod electrodes currently offered within the metal-coated steel-rod category, the

industry has a relatively new alternative with UL-listed hot-dip galvanized (zinc-coated)

ground-rod electrodes.

According to David Prior, technical services manager at Galvan Industries-which

manufactures all three types of metal-coated rods-Underwriters Laboratories has listed the

hot dip galvanized ground rod electrode to UL 467, ensuring the same critical criteria is

mandated for the galvanized rods as the copper-coated rods currently listed.

“Since the 5/8-inch nominal diameter copper-clad and hot-dip galvanized rods are produced

fundamentally from the same steel core, the only difference is the coating,” said Prior. “The

intention of UL 467 is to provide conformity testing of the rod throughout the industry.”

Before the introduction of the listed galvanized ground rod, most manufacturers produced the

ground rods to an ANSI C135.30 specification, which expired in 1993 and did not meet the

NEC. The listed galvanized ground rod, Prior said, meets the strictest interpretation of the

NEC.

All rod-type grounding electrodes or “ground rods” are manufactured from a steel core with a

nonferrous coating to guard the steel. To protect the industry against poor-quality steel,

Galvan and other NEMA members developed the ANSI-approved NEMA GR-1 in 2001 ground-rod

specification, which established minimum acceptable performance criteria.

Eliminating coating controversy

Electrical codes allow users to specify either bare or coated grounding electrodes. UL-

approved coatings include copper, zinc or stainless steel. Galvanized rods have a zinc coating

thickness of 3.9 mils (.0039 in. or 710 g/m2) and copper rods are coated to a thickness of 10

mils or 0.01 in.

Technical information indicates that hot-dip galvanized coatings are formed through a

diffusion reaction between iron and zinc resulting in a metallurgical bond of the two metals.

Copper is electrodeposited as a pure copper coating bonded to the steel's surface.

Within the industry a difference of opinion stems from a belief that copper cladding is superior

because its thicker coating offers better conductivity of fault than zinc and provides longer

life due to better corrosion resistance. The difference in conductivity between copper and zinc

coatings is statistically insignificant, according to IEEE-80, said Prior. Either coating is

capable of safely conducting fault to ground.

“With regards to life expectancy, state departments of transportation have used buried

galvanized steel culvert bridges for decades. If galvanized steel could only be expected to last

15 years, our transportation system along secondary roads would have been closed to traffic

permanently long ago,” Prior said.

According to the National Association of Corrosion Engineers, the galvanic or electromotive

force (EMF) scale of metals illustrates in ascending order the more-noble metals to less-noble

metals. Copper is more noble than steel and zinc.

“Less-noble metals are sacrificial to more-noble metals when they are connected in a

corrosion cell. That means a steel core will sacrifice itself to protect the copper coating if it's

damaged while being driven into the soil. Zinc is less noble or anodic and will sacrifice itself

preferentially to protect the steel core if the coating is damaged,” Prior said.

Prior pointed out that neither galvanizing nor copper cladding of steel ground rods provide the

ultimate protection against corrosion in soil. Other environmental considerations such as pH,

electrical resistivity, moisture, stray AC or DC current, and dissimilar metals are additional

factors that influence corrosion.

Prior added, “Each application must be evaluated by a qualified engineer based upon the local

conditions experienced at the job site. There are instances where copper will be the logical

choice and others where galvanizing is the most effective. I wouldn't advise using a

galvanized rod in a coastal environment with heavy chloride contamination adjacent to it, nor

using copper rods adjacent to galvanized steel screw anchors.”

Passing inspections

According to, director of education of the International Association of Electrical Inspectors,

all grounding installations, especially those performed for remodels, retrofits, service changes

or new construction, are generally subject to electrical inspection for NEC compliance.

“From a Code standpoint, the NEC has been relatively silent on the Code requirements that

relate to lightning protection systems; however, the NEC requirements (Sections 250.60 and

250.106) cover the materials and bonding of the electrode of a power distribution system to

the ground terminal of a lightning protection system on the same structure,”.

The requirements for lightning protection systems are provided in NFPA 780-2004 Standard for

the Installation of Lightning Protection Systems.

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.

While the initial inspection of the rod serves a purpose, the bigger issue is inspection of the

rod 5, 10 or 30 years after it is buried. Who performs this important role? Nobody. UL marks

are not helpful once the rod is buried. The long-term performance of the rod is more important

than its initial inspection.

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. Rod size and depth-Minimum diameters must be met, but the

single most important factor in grounding, and it the length, with at least one 8-foot rod driven

flush with the earth. Provision in NEC Section 250.53(G) can be referenced where rock bottom

is encountered presenting difficulties with a driven perpendicular installation.

_ Resistance-The Code as a minimum requires that where a single rod, pipe or plate electrode

is used, the connection to the earth not have a resistance greater than 25 ohms (250.56). A

single rod-, pipe- or plate-grounding electrode that produces greater resistance should be

augmented by an additional electrode of any of the types specified in 250.52(A)(2)-(A)(7),

which many local jurisdictions mandate.

_ Connections-Connections to the rod-type electrodes generally must be listed and

compatible both with the material of the rod and the conductor used (250.70).

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.

Why use UL Listed ground rods when NEC doesn't require them?

FACT: Rods at least 0.625 inches in diameter and 8 feet long meets NEC, but beware of

imposters. Copper rods that are 0.600 inches in diameter or less, that don't have 10

mils of copper do not meet code, but without the UL stamp, you don't know what the

coating thickness actually is. Rods that aren't fully 8-feet long also do not meet code,

but once the rod has been driven it is difficult for inspectors to tell its length. The UL

mark - with factory ID - is the only sure way to know your rod is fully code compliant.

What is the value of the UL certification on a ground rod electrode?

FACT: Certification of a ground rod assures your product was built to comply with NEC

standards. It also simplifies inspections for the AHJ inspector since special tools and

equipment are not required to ensure compliance with code. The best approach is to

review where the electrode will be installed and which parameters could influence

service life - soil pH, electrical resistivity, moisture, stray current and proximity of

dissimilar metals. Use good engineering to determine the best rod for your installation.

Called "tunneling," this is caused by a corrosive environment in the area of the

installed rod. It's why an analysis is needed -- so you select the best type of electrode

for your area. A better choice: installing a stainless steel rod: it costs more but it offers

more system reliability and safety.

An expert on lightning protection showed a much-deteriorated galvanized rod and a

copper-coated rod only slightly deteriorated - both installed near Las Vegas. Doesn't

this show galvanized ground rod's shorter life?

Soil conditions vary region to region. Galvanized rods are not the best choice in coastal

installations and where soil pH is high. Copper-coated rods are a poor fit in certain clay

soils that degrade protective coatings and in rocky conditions that can damage

coatings to the steel rod core. While the 0.625 inch galvanized rod is attracting some

interest, there is no engineering sense for making the galvanized rod larger than the

same nominal diameter as the copper-coated rod. While the rod diameter is NEC- and

NESC-compliant, rod length may not meet the code. For rods that are not certified and

listed, the inspector will have to dig down to determine compliance. Another possible

drawback: lack of compatibility between rods, clamps and couplings when driving

multiple rods to depth.

Various soil parameters are key to rod selection. Comprehensive engineering analysis

is best to maximize equipment protection, system reliability and personnel safety!

Copper-coated ground rods must be 0.625 inch finished diameter with any coating type,

or greater than 0.500 finished diameter and listed (e.g. UL). UL specifies 10-mils

minimum coating; anything under 10 mils can't be UL Listed and violates NEC. UL

Listed rods comply with both GR-1 2001 and GR-1 2005. Surface degradation depends

on soil parameters, electrical stray voltage, buried materials and more. Start by

reviewing the "electromotive series of metals" which defines the nobility of various

metals. We know that corrosion proceeds from the anodic, or less noble coating to the

cathodic, the most noble coating. Zinc sacrifices to steel; steel sacrifices to copper.

So what happens when the coating is damaged to the rod steel core? Zinc coatings

offer a tougher surface for driving into rocky soil conditions due to the nature of hot-dip

galvanizing.

AST grounding requirements are not consistent in the following documents:

API RP 545 – Recommended Practice for Lightning Protection of Aboveground Storage Tanks

for Flammable and Combustible Liquids, 1st Edition, October 2009.

API Standard 2003 – Protection Against Ignitions Arising Out of Static, Lightning and Stray

Currents, 7th Edition January 2008.

NFPA 780 – Standard for the Installation of Lightning Protection Systems, 2008 Edition.

API Standard 650 – Welded Tanks for Oil Storage, 11th Edition w/Addendum2, May 1, 2010

• API 2003 does not speak to tank size, but does mention that when a tank is not

grounded (such as with a nonconductive membrane and not connected to a grounded

piping system) supplemental grounding is required to prevent damage to insulating

materials and foundation.

API 650 does not require supplementary grounding,

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.

Service 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.

Perhaps a less intuitive leap is that copper is inherently more resistant to corrosion than zinc.

We’ve all used galvanized steel products and paid a premium for them. Chances are, you didn’t

have any major corrosion problems with these items. Why should we expect anything different

from a galvanized ground rod? The reason is that galvanized ground rods are exposed to the

much harsher below-grade environment.

It is an entirely different corrosion ballgame when metals are buried. Aluminum illustrates this

point perfectly. Aluminum displays good corrosion resistance above grade. In fact, many boats

that are subject to corrosive saltwater are made using aluminum. However, aluminum is

prohibited for below-grade use in Article 250 of the NEC due to its lack of corrosion resistance

in this environment. While not as drastic as aluminum, galvanized metal experiences a similar

drop off in corrosion resistance when placed underground.

Comprehensive direct burial studies done by the National Bureau of Standards showed that

3.9 mils of galvanizing could be expected to provide 10-13 years of protection in most soils.

This same study showed that 10 mils of copper could be expected to last more than 40 years

in most soil types and is the basis for the 10 mils of copper required for a rod to be UL listed.

Furthermore, independent ground rod testing performed by the Navy and the National

Electrical Grounding Research Project back up the data gathered by the National Bureau of

Standards. Because of these studies, a service life of 10 to 15 years can be assigned to

galvanized rods and 40-plus years for 10 mil copper-bonded rods in most soil types.

These results may lead you to believe that copper-bonded rods are better than galvanized

rods. Sometimes this is true and sometimes not. I want to emphasize the importance of

matching the appropriate ground rod to the application. If the facility being grounded has a life

expectancy of less than 15 years, a galvanized ground rod is appropriate and will provide the

most cost-effective solution. For installations with a longer service life, copper-bonded ground

rods are the best fit. For many years, the copper cold water pipe has served as the primary

grounding electrode for commercial & residential grounding.

With non-conductive PVC piping used more extensively these days, the supplemental ground

rod is becoming the primary electrode. It only makes sense that it should be required to

perform as long as the copper water pipe that came before it. As such, I strongly encourage

the use of UL-listed copper-bonded ground rods on new home construction.

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.

While the initial inspection of the rod serves a purpose, the bigger issue is inspection of the

rod 5, 10 or 30 years after it is buried. Who performs this important role? Nobody. UL marks

are not helpful once the rod is buried. The long-term performance of the rod is more important

than its initial inspection.

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.