a guide to electrical safety - · pdf filea guide to electrical safety n.c. department of...

A Guide to

Electrical Safety

N.C. Department of LaborDivision of Occupational Safety and Health

4 W. Edenton St.Raleigh, NC 27601-1092

Cherie K. BerryCommissioner of Labor

N.C. Department of LaborOccupational Safety and Health Program


OSHA State Plan Designee

To obtain additional copies of this book, or if you havequestions about N.C. occupational safety and healthstandards or rules, please contact:

N.C. Department of LaborBureau of Education, Training and Technical Assistance

4 W. Edenton St.Raleigh, NC 27601-1092

Phone: (919) 807-2875 or 1-800-NC-LABOR____________________

Additional sources of information are listed on theinside back cover of this book.

____________________The projected cost of the OSHNC program for federal fiscal year 2002–2003is $13,130,589. Federal funding provides approximately 37 percent($4,920,000) of this total.

Printed 4/98, 5M

A Guide to Electrical Safety was written by EdMendenhall, owner of Mendenhall Technical Services,Bloomingdale, Illinois. Mr. Mendenhall, an engineerand Certified Safety Professional, has over 35 years ofexperience in safety and health management.Additional material was provided by OSHNC elec-tronics technician Dwight Grimes. This guide isintended to be consistent with existing state and fed-eral OSHA standards. Therefore, if the reader consid-ers a statement to be inconsistent with a standard,then the OSHA standard should be followed.

ContentsPart Page

Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1iiv

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1ii1

2 Fundamentals of Electricity . . . . . . . . . . . . . . . .1ii3

3 Branch Circuit Wiring . . . . . . . . . . . . . . . . . . . . . . . ii14

4 Branch Circuit and Equipment Testing. . . ii27

5 Voltage Detector Testing. . . . . . . . . . . . . . . . . . . . . ii34

6 Ground Fault Circuit Interrupters . . . . . . . . . ii38

7 Common Electrical Deficiencies . . . . . . . . . . . . ii44

8 Inspection Guidelines/Checklist . . . . . . . . . . . . ii51

9 Safety Program Policy and Procedures......ii55

iii

ForewordEveryone from office clerks to farmers work around

electricity on a daily basis. Our world is filled with over-head power lines, extension cords, electronic equipment,outlets, and switches. Our access to electricity hasbecome so common that we tend to take our safety forgranted. We forget that one frayed power cord or apuddle of water on the floor can take us right into theelectrical danger zone.

A Guide to Electrical Safety can help electricians,plant maintenance personnel, and many others reviewsafe procedures for electrical work. It also covers themain OSHA standards concerning electrical safety onthe job.

In North Carolina, state inspectors enforce the feder-al laws through a state plan approved by the U.S.Department of Labor. The North Carolina Departmentof Labor’s Division of Occupational Safety and Health(OSHNC) is charged with this mission. OSHNCenforces all current OSHA standards. It offers manyeducational programs to the public and produces publi-cations, including this guide, to help inform peopleabout their rights and responsibilities regarding OSHA.

When reading through this guide, please rememberOSHA’s mission is greater than just to enforce regula-tions. An equally important goal is to help citizens findways to create safer workplaces. A Guide to ElectricalSafety can help you make and keep your workplace freeof dangerous electrical hazards.


iv

1Introduction

Electricity is the modern version of the genie inAladdin’s lamp. When electricity is safely contained inan insulated conductor, we normally cannot see, smell,taste, feel, or hear it. It powers an endless list of labor-saving appliances and life-enhancing and support sys-tems that have become such an assumed part of ourlives that we give little thought to its potential for caus-ing harm. Many myths and misstatements about elec-trical action are accepted as fact by many people.

For a recent five-year period, the National SafetyCouncil reported that workplace electrocutions account-ed for 7 percent of all work-related fatalities. Work-related electrical fatalities are a recurring and veryserious problem in North Carolina and throughout theUnited States.

The National Institute for Occupational Safety andHealth (NIOSH) conducted a study of workplace elec-trocutions that revealed the following information aboutworkers who were electrocuted:

• The average age was 32

• 81 percent had a high school education

• 56 percent were married

• 40 percent had less than one year of experience onthe job to which they were assigned at the time ofthe fatal accident

• 96 percent of the victims had some type of safetytraining, according to their employers

This information reminds us that more effectivetraining and education must be provided to employees ifwe are to reduce workplace electrocution hazards.

1

Employees should receive initial training then refresherelectrical hazard recognition training on an annualbasis.

In addition to the shock and electrocution hazards,electricity can also cause fires and explosions. Accordingto the U.S. Consumer Product Safety Commission, anestimated 169,000 house fires of electrical origin occureach year, claiming 1,100 lives and injuring 5,600 per-sons. Property losses from fires begun by electricity areestimated at $1.1 billion each year. The safe use andmaintenance of electrical equipment at work (and athome) will help prevent fire and physical injury.

The purpose of this guide is to provide a clear under-standing of electrical action and its control in the work-place environment. This information will enable you torecognize electrical hazards in the workplace as well asprovide information on their control and/or elimination.The guide does not qualify a person to work on ornear exposed energized parts. Training require-ments for “qualified” persons (those permitted towork on or near exposed energized parts) aredetailed in 29 CFR 1910.332(b)(3). The guide will,however, enhance your ability to find and reportelectrical deficiencies in need of a qualified per-son’s attention.

2

2Fundamentals of ElectricityA review of the fundamentals of electricity is neces-

sary to an understanding of some common myths andmisstatements about electricity. First we must reviewOhm’s Law and understand the effects of current on thehuman body. Basic rules of electrical action willenhance your ability to analyze actual or potential elec-trical hazards quickly. This information will also enableyou to understand other important safety concepts suchas reverse polarity, equipment grounding, ground faultcircuit interrupters, double insulated power tools, andtesting of circuits and equipment.

Ohm’s LawThere are three factors involved in electrical action.

For electrons to be activated or caused to flow, thosethree factors must be present. A voltage (potential dif-ference) must be applied to a resistance (load) to causecurrent to flow when there is a complete loop or circuitto and from the voltage source. Ohm’s Law simplystates that one volt will cause a current of one ampereto flow through a resistance of one ohm. As a formulathis is stated as follows:

Voltage (E) = Current (I) Resistance (R).

We will be concerned about the effects of current onthe human body, so the formula relationship we will usemost will be I = E/R. When you analyze reported shockhazards or electrical injuries, you should look for a volt-age source and a resistance (high or low) ground loop.The human body is basically a resistor and its resis-tance can be measured in ohms. Figure 1 depicts a bodyresistance model. The resistive values are for a persondoing moderate work. An increase in perspiration

3

caused from working at a faster work pace woulddecrease the resistance and allow more current to flow.

Figure 1

Human Body Resistance Model

As an example, let’s use the hand to hand resistanceof the body model, 500 + 500 = 1,000 ohms. Using I =E/R, I = 120/1,000 (assuming a 120 volt AC (alternatingcurrent) power source) or 0.120 amps. If we multiply0.120 amps by 1,000 (this converts amps to milliamps),we get 120 milliamps (ma) which we will refer to in fig-ure 2. If a person were working in a hot environment,and sweating, the body resistance could be lowered to avalue of 500 ohms. Then the current that could flowthrough the body would equal I = 120/500 or 0.240amps. Changing this to milliamps, 1,000 0.240 = 240ma. This means that we have doubled the hazard to thebody by just doing our job.

This can be explained by looking at figure 2. Figure 2plots the current flowing through the chest area and thetime it takes to cause the heart to go into ventricular

4

500Ω 500Ω

500Ω500Ω

100Ω

fibrillation (arrhythmic heartbeat). Using the exampleof the body resistance at 1,000 ohms allowing 120 ma toflow (follow the dark line vertically from 120 ma to theshaded area, then left to the time of 0.8 seconds), youcan see that it would only take 0.8 seconds to causeelectrocution. When the body resistance is 500 ohms,at 240 ma it would only take 0.2 seconds to causeelectrocution. Variable conditions can make common-use electricity (110 volts, 15 amps) fatal.

Current and Its Effect on the HumanBody

Based on the research of Professor Dalziel of theUniversity of California, Berkeley, the effect of 60 Hz(cycles per second) of alternating current on the humanbody is generally accepted to be as follows:

5

Figure 2

Electrical Current (AC) Versus the Time It Flowsthrough the Body

Tim

e In

Sec

onds

10.0

6.0

2.0

1.0

0.6

.2

.1

.06

.02

.01

‘Let Go’Range

Current In Milliamperes

Maximum PermittedBy UL For Class A GFCI

Electrocution ThresholdFor Typical Adult

0 20 40 60 80 100 120 140 160 180 200 220 240 260

• 1 milliamp (ma) or less—no sensation—not felt(1,000 milliamps equal 1 amp)

• 3 ma or more painful shock• 5 ma or more—local muscle contractions—50 per-

cent cannot let go• 30 ma or more—breathing difficult—can cause

unconsciousness• 50–100 ma—possible heart ventricular fibrillation• 100–200 ma—certain heart ventricular fibrillation• 200 ma or over—severe burns and muscular con-

tractions—heart more apt to stop than fibrillate• Over a few amps—irreversible body damage

Thus, we can see that there are different types ofinjuries that electricity can cause. At the 20 to 30 marange a form of anoxia (suffocation) can result. Thiscould happen in a swimming pool where there is aground loop present (the drain at the bottom of the pool)if a faulty light fixture or appliance is dropped into thewater. Current would flow from the light fixture to thedrain, using the water as the conducting medium. Anyperson swimming through the electrical field created bythe fault current, would be bathed in potential differ-ence and the internal current flow in the body couldparalyze the breathing mechanism. This is why it isvery important to keep all portable electrical appliancesaway from sinks, tubs, and pools.

Ventricular fibrillation generally can occur in therange of 50 to 200 ma. Ventricular fibrillation is therepeated, rapid, uncoordinated contractions of the ven-tricles of the heart resulting in the loss of synchroniza-tion between the heartbeat and the pulse beat. Onceventricular fibrillation occurs, death can ensue in a fewminutes. Properly applied CPR (cardiopulmonary resus-citation) techniques can save the victim until emergencyrescue personnel with a defibrillator arrive at the scene.Workers in the construction trades and others workingwith electrical power tools should receive CPR training.

6

Above a few amperes, irreversible body damage canoccur. This condition is more likely to occur at voltagesabove 600 volts AC. For example, if a person contacted10,000 volts, I = 10,000/1,000 = 10 amps. This amountof current would create a great amount of body heat.Since the body consists of over 60 percent water, thewater would turn to steam at a ratio of approximately 1to 1,500. This would cause severe burns or exploding ofbody parts. These are the types of injuries that youwould normally associate with electric power companyworkers. They can also occur, however, when peopleaccidentally let a television or radio antenna contact anuninsulated power line. Accidents involving mobile ver-tical scaffolding or cranes booming up into power linescan cause these types of injuries or fatalities.

The route that the current takes through the bodyaffects the degree of injury. If the current passesthrough the chest cavity (i.e., left hand to right hand),the person is more likely to receive severe injury or elec-trocution; however, there have been cases where an armor leg was burned severely when the extremity came incontact with the voltage and the current flowed througha portion of the body without going through the chestarea of the body. In these cases the person received asevere injury but was not electrocuted.

Typical 120 Volt AC SystemAt some time in your life, you may have received an

electrical shock. Figure 3 illustrates a typical 120 voltAC system. Somewhere near your home or workplacethere is a transformer with wires going between thetransformer and the service entrance panel (SEP). Insmall establishments and homes, the SEP may alsocontain circuit breakers or fuses to protect the circuitsleaving the SEP. Typical overcurrent protection forthese circuits would be 15 or 20 amps. This protection isdesigned for line (hot) to line (grounded conductor)

7

faults that would cause current greater than 15 or 20amps to flow. If a person accidentally contacted the“hot” conductor while standing on the ground with wetfeet (see figure 3), a severe shock could result. Currentcould flow through the body and return to the trans-former byway of the “ground loop” path. Most electricalshocks result when the body gets into a ground loop andthen contacts the “hot” or ungrounded conductor. If youanalyze electrical shock incidents, look for these twofactors: a ground loop and a voltage source.

We normally think of ground as the earth beneathour feet. From an electrical hazard standpoint, groundloops are all around us. A few ground loops that maynot be under our feet include: metal water piping, metaldoor frames in newer building construction, ventilationducts, metal sinks, metal T-bars holding ceiling acousti-cal panels, wet or damp concrete floors and walls,grounded light fixtures, and grounded powertools/appliances. When you are using or working aroundelectrical equipment, be alert to these and other groundloops. The person shown in figure 3 could have isolatedthe ground loop by standing on insulated mats or dryplywood sheets. Wearing dry synthetic soled shoeswould also have isolated the ground loop.

8

Figure 3

AC Systems—Contact with “Hot” Conductor

Primary Lines2.4-13 kV

“Hot” Conductor(black or red)

GroundedConductor

(white or gray)Circuit Breaker

Equipment-groundingConductor (green or bare)

Grounding Electrode

Neutral

UtilitySupplyServiceGround

The utility supply ground and the grounding elec-trode conductor are system safety grounds. Thesegrounds protect the users of electrical equipment incase of lightning storms and in instances where highvoltage lines accidentally fall on lower voltage lines.These system safety grounds are not designed for indi-vidual safety. Actually, they are a hazard to the individ-ual in that it is very easy to get into a ground loop, andonce into a ground loop, you only need one fault path tothe hot conductor before shock or injury can result.

Four Principles of Electrical ActionKnowing the basic principles of electrical action will

help you understand and evaluate electrical shock haz-ards. These principles and an explanation for each areas follows:

1. Electricity does not “spring” into action until cur-rent flows.

2. Current will not flow until there is a loop (inten-tionally or accidentally) from the voltage source toa load and back to the source.

3. Electrical current always returns to the voltagesource (transformer) that created it.

4. When current flows, energy (measured in watts)results.

Explanation for Principle 1

A person can contact voltage and not be shocked ifthere is high resistance in the loop. In figure 3, the per-son is standing on the ground and touching the 120 voltconductor. That would cause a shock and make yourhair stand on end. If that same person were standing oninsulated mats or wore shoes with insulated soles, theperson would not be shocked even though there was 120volts in his or her body. This explains why a person canbe working outside with a defective power tool and not

9

receive a shock when the ground is very dry or the per-son is isolated from a ground loop by plywood. Thatsame person with the same power tool could changework locations to a wet area, then receive a shock whencontacting a ground loop of low resistance. As previous-ly stated, 3 ma or more can cause painful shock. UsingOhm’s Law I = E/R, 120 volts, and 3 ma, we can calcu-late how much resistance would allow 3 ma of currentto flow. R = E/I or 120/0.003 or R = 40,000 ohms. Anyground loop resistance of less than 40,000 ohms wouldallow a shock that could be felt. This principle can alsoexplain why birds sitting on a power line are not elec-trocuted. Their bodies would receive voltage, but cur-rent would not flow since another part of their body isnot in contact with a ground loop.


For current to flow, a complete loop must be estab-lished from the voltage source to the person and back tothe voltage source. In figure 3, the loop is through theperson’s hand touching a 120 volt conductor, throughthe body to ground and then through the groundingelectrode and back to the transformer secondarythrough the neutral conductor. Once that loop is estab-lished and becomes less than 40,000 ohms, a shock orserious injury can result. If the loop can be interrupted,as noted in Principle 1, then current will not flow. Thesetwo principles give you a common sense way to figureout how and why someone received a shock and theaction that should be taken to prevent future shocks ofthe same type.


Electric current always seeks to return to the trans-former that created it. Current will also take all resis-tive paths to return to the transformer that created it.Since the voltage source has one wire already connectedto ground (figure 3), contact with the “hot” wire pro-

10

vides a return path for current to use. Other groundloop paths in the workplace could include metal ducts,suspended ceiling T-bars, water pipes, and other similarground loops.


This principle explains the shock and injury to thehuman body that current can do. The higher the voltageinvolved, the greater the potential heat damage to thebody. As previously mentioned, high voltage can causehigh current flow resulting in severe external and inter-nal body damage. Remember that the flow of currentcauses death or injury; voltage determines how theinjury or death is effected.

Some Misconceptions about ElectricalAction

Americans use more electrical power per person thando individuals of any other country in the world, butthat does not mean that we have a better understand-ing of electricity. Some common misconceptions aboutelectrical actions are addressed and corrected in the fol-lowing discussion.

“If an Appliance or Power Tool Falls into Water,It Will Short Out”

When an appliance falls into a tub or container ofwater, it will not short out. In fact, if the applianceswitch is “on,” the appliance will continue to operate. Ifthe appliance has a motor in it, the air passage to keepthe motor cool will be water cooled. Unfortunately, thatsame air passage, when wet, will allow electricity toflow outside the appliance if a current loop is present(such as a person touching the metal faucet and reach-ing into the water to retrieve a hair dryer). The currentloop due to the water resistance will be in the 100 to300 ma range, which is considerably less than the

11

20,000+ ma needed to trip a 20 amp circuit breaker.Since an appliance will not short out when dropped in asink or tub, no one should ever reach into the water toretrieve an appliance accidentally dropped there. Thewater could be electrified, and a person touching agrounded object with some other part of the body couldreceive a serious shock depending on the path the cur-rent takes through the body. The most important thingto remember is that appliances do not short out whendropped or submerged in water.

“Electricity Wants to Go to the Ground”

Sometimes editors of motion films about electricalsafety make the statement that “electricity wants to goto the ground.” There are even books published aboutelectrical wiring that contain the same statement. Aspreviously stated, electricity wants to return to thetransformer that created it, and the two conductors thatwere designed to carry it safely are the preferred routeit takes. Whenever current goes to ground or any otherground loop, it is the result of a fault in the appliance,cords, plugs, or other source.

“It Takes High Voltage to Kill;120 Volts AC Is Not Dangerous”

Current is the culprit that kills. Voltage determinesthe form of the injury. Under the right conditions, ACvoltage as low as 60 volts can kill. At higher voltagesthe body can be severely burned yet the victim couldlive. Respect all AC voltages, high or low, as having thepotential to kill.

“Double Insulated Power Tools Are Doubly Safeand Can Be Used in Wet and Damp Locations”

Read the manufacturer’s operating instructions care-fully. Double insulated power tools are generally madewith material that is nonconductive. This does give theuser protection from electrical faults that occur withinthe insulated case of the appliance. However, double

12

insulated power tools can be hazardous if dropped intowater. Electrical current can flow out of the power toolcase into the water. Remember that double insulatedpower tools are not to be used in areas where they canget wet. If conditions or situations require their useunder adverse conditions, use GFCI (ground fault cir-cuit interrupter) protection for the employee.

13

3Branch Circuit Wiring

DefinitionsDiscussion of wiring methods must be preceded by an

understanding of terms used to define each specific con-ductor in a typical 120/240 volt AC system. Refer to fig-ure 4 for an example of most of the following definitions.The National Electrical Code (NEC) is used as the refer-ence source.

Ampacity. The current (in amps) that a conductorcan carry continuously under the conditions of use with-out exceeding its temperature rating. When you findattachment plugs, cords, or receptacle face plates thatare hot to touch, this may be an indication that toomuch of a load (in amps) is being placed on that branchcircuit. If the insulation on the conductors gets too hot,it can melt and cause arcing, which could start a fire.

Attachment Plug. Describes the device (plug) thatwhen inserted into the receptacle establishes the elec-trical connection between the appliance and branchcircuit.

Branch Circuit. The electrical conductors betweenthe final overcurrent device (the service entrance panel(SEP) in figure 4) protecting the circuit and the recepta-cle. The wiring from the SEP to the pole mounted trans-former is called the “service.”

Circuit Breaker. Opens and closes a circuit bynonautomatic means as well as being designed to openautomatically at a predetermined current withoutcausing damage to itself. Be alert to hot spots in circuitbreaker panels indicating that the circuit breaker isbeing overloaded or that there may be looseconnections.

14

Equipment. A general term for material, fittings,devices, appliances, fixtures, apparatus, and the likeused as a part of, or in connection with, an electricalinstallation. In figure 4, the SEP and any associatedconduit and junction boxes would be consideredequipment.

Feeder. The term given to the circuit conductorsbetween the SEP and the final branch circuit overcur-rent device. In figure 4 there is no feeder since the SEPis also the final branch circuit overcurrent device.

Figure 4

Branch Circuit Wiring

Ground. A conducting connection (whether inten-tional or accidental) between an electrical circuit orequipment and the earth, or to some conducting bodythat serves in place of the earth. It is important toremember that a conducting body can be in the ceilingand that we must not think of ground as restricted toearth. This is why maintenance personnel may not real-ize that a ground loop exists in the space above a dropceiling, due to the electrical conduit and other groundedequipment in that space.

15

Primary Lines2.4-13 kV

“Hot” Conductor(black or red)

GroundedConductor

(white or gray)

Circuit Breaker

Equipment-groundingConductor (green or bare)

Grounding ElectrodeConductor on Premises

Neutral

UtilitySupplyServiceGround

Typical PoleTransformer

ServiceEntrance

Panel

Nickel orLight-colored

Terminal

GreenHexagonal-headTerminal Screw

Brass coloredTerminal

Grounded Conductor. The conductor in the branchcircuit wiring that is intentionally grounded in the SEP.This conductor is illustrated in figure 4. From the SEPto the transformer the same electrical path is referredto as the neutral. From the final overcurrent device tothe receptacle the conductor is referred to as thegrounded conductor.

Grounding Conductor, Equipment. The conductorused to connect the noncurrent-carrying metal parts ofequipment, raceways, and other enclosures to the sys-tem grounded conductor at the SEP. The equipmentgrounding conductor path is allowed to be a separateconductor (insulated or noninsulated), or where metalconduit is used, the conduit can be used as the conduc-tor. There are some exceptions to this such as in hospi-tal operating and intensive care rooms. The equipmentgrounding conductor is the human safety conductor ofthe electrical system in that it bonds all noncurrent-carrying metal surfaces together and then connectsthem to ground. By doing this we can prevent a voltagepotential difference between the metal cabinets andenclosures of equipment and machinery. This conductoralso acts as a low impedance path (in the event of avoltage fault to the equipment case or housing) so thatif high fault current is developed, the circuit breaker orfuse will be activated quickly.

Grounding Electrode Conductor. Used to connectthe grounding electrode to the equipment groundingconductor and/or to the grounded conductor of the cir-cuit at the service equipment or at the source of aseparately derived system (see figure 4).

Overcurrent. Any current in excess of the rated cur-rent of equipment or the ampacity of a conductor is con-sidered overcurrent. This condition may result from anoverload, short circuit, or a ground fault.

16

Wiring MethodsThe NEC requires the design and installation of elec-

trical wiring to be consistent throughout the facility. Toaccomplish this, it is necessary to follow NEC require-ments. For 120 volt grounding-type receptacles, thefollowing wiring connections are required (see figure 4).

• The ungrounded or “hot” conductor (usually withblack or red insulation) is connected to the brasscolored terminal screw. This terminal and themetal tension springs form the small slot receiverfor any appliance attachment plug. An easy way toremember the color coding is to remember “blackto brass” or the initials “B & B.”

• The “grounded conductor” insulation is generallycolored white (or gray) and should be fastened tothe silver or light colored terminal. This terminaland the metal tension springs form the large slotfor a polarized attachment plug. An easy way toremember this connection is to think “white tolight.”

• The equipment grounding conductor path can be aconductor, or where metal conduit is used, the con-duit can be substituted for the conductor. If the lat-ter is used, you must monitor the condition of theconduit system to ensure that it is not damaged orbroken. Any “open” in the conduit system will elim-inate the equipment grounding conductor path.Additionally, the condition of the receptacles mustbe monitored to ensure that they are securely fas-tened to the receptacle boxes. When a third wire isrun to the receptacle either in a conduit or as apart of a nonmetallic sheathed cable assembly, theconductor must be connected to the green coloredterminal on the receptacle.

These wiring methods must be used to ensure thatthe facility is correctly wired. Circuit testing methods

17

will be discussed in part 4. In older homes, knob andtube or other two-wire systems may be present. TheNEC requires that grounding type receptacles be usedas replacements for existing nongrounding types and beconnected to a grounding conductor. An exception isthat where a grounding means does not exist in theenclosure, either a nongrounding or a GFCI-type recep-tacle must be used. A grounding conductor must not beconnected from the GFCI receptacle to any outlet sup-plied from the GFCI receptacle. The exception furtherallows nongrounding type receptacles to be replacedwith the grounding type where supplied through aGFCI receptacle.

Plug and Receptacle ConfigurationsAttachment plugs are devices that are fastened to the

end of a cord so that electrical contact can be madebetween the conductor in the equipment cord and theconductors in the receptacle. The plugs and receptaclesare designed for different voltages and currents, so thatonly matching plugs will fit into the correct receptacle.In this way, a piece of equipment rated for one voltageand/or current combination cannot be plugged into apower system that is of a different voltage or currentcapacity.

The polarized three-prong plug is designed with theequipment grounding prong slightly longer than thetwo parallel blades. This provides equipment groundingbefore the equipment is energized. Conversely, whenthe plug is removed from the receptacle, the equipmentgrounding prong is the last to leave, ensuring a ground-ed case until power is removed. The parallel line bladesmaybe the same width on some appliances since thethree-prong plug can only be inserted in one way. Aserious problem results whenever a person breaks orcuts off the grounding prong. This not only voids thesafety of the equipment grounding conductor but allows

18

the attachment plug to be plugged in with the correctpolarity or with the wrong polarity.

Figure 5 illustrates some of the National ElectricalManufacturers Association (NEMA) standard plug andreceptacle connector blade configurations. Each configu-ration has been developed to standardize the use ofplugs and receptacles for different voltages, amperes,and phases from 115 through 600 volts and from 10through 60 amps, and for single and three-phasesystems.

Figure 5

Plug and Receptacle Configurations

You should be alert to jury-rigged adaptors used tomatch, as an example, a 50 amp attachment plug to a20 amp receptacle configuration. Using these adaptorsposes the danger of mixing voltage and current ratingsand causing fire and/or shock hazards to personnel

19

15-Ampere Plug

20-Ampere Plug,125-Volt Receptaclesand Plugs

125/250-Volt, 30-AmpereReceptacle and Plug

125/250-Volt, 50-AmpereReceptacle and Plug

250-Volt, 30-AmpereReceptacle and Plug

15 Ampere

20 Ampere

Only

5-15R 5-15P

5-20R 5-20P

10-30R 10-30P

6-30R 6-30P10-50R 10-50P

Either

using equipment. Equipment attachment plugs andreceptacles should match in voltage and current ratingsto provide safe power to meet the equipment ratings.Also the attachment plug cord clamps must be securedto the cord to prevent any strain or tension from beingtransmitted to the terminals and connections inside theplug.

Understanding Reverse PolarityThe NEC recognizes the problem of reverse polarity.

It states that no grounded conductor may be attached toany terminal or lead so as to reverse the designatedpolarity. Many individuals experienced with electricalwiring and appliances think that reverse polarity is nothazardous. A few example situations should heightenyour awareness of the potential shock hazard fromreverse polarity.

An example of one hazardous situation would be anelectric hand lamp. Figure 6 illustrates a hand lampimproperly wired and powered.

Figure 6

Hand Lamp—Reverse Polarity

When the switch is turned off, the shell of the lampsocket is energized. If a person accidentally touched theshell (while changing a bulb) with one hand andencountered a ground loop back to the transformer, ashock could result. If the lamp had no switch and was

20

Equipment Plug

Receptacle

Ground Potential

Metal Guard

Bulb

SwitchOFF Position

TransformerSEP “Hot”

“Hot”

120 Volt

plugged in as shown, the lamp shell would be energizedwhen the plug was inserted into the receptacle. Manytwo-prong plugs have blades that are the same size, andthe right or wrong polarity is just a matter of chance. Ifthe plug is reversed (figure 7), the voltage is applied tothe bulb center terminal and the shell is at groundpotential. Contact with the shell and ground would notcreate a shock hazard in this situation. In this examplethe hand lamp is wired correctly.

Figure 7

Hand Lamp—Correct Polarity

Another example is provided by electric hair dryersor other plastic-covered electrical appliances. Figure 8illustrates a hair dryer properly plugged into a recepta-cle with the correct polarity.

Figure 8

Hair Dryer—Correct Polarity

21

Equipment Plug

Receptacle

Ground Potential

Metal Guard

Bulb

SwitchOFF Position

TransformerSEP “Hot”

“Hot”

“Hot”

120 Volt

Receptacle

Hair Dryer

Plug

Switch

ServiceEntryPanel(SEP)

“Hot”

“Hot”Transformer

120 Volt

You will notice that the switch is single pole-singlethrow (SPST). When the appliance is plugged in withthe switch in the hot or 120 volt leg, the voltage stops atthe switch when it is in the off position. If the hairdryer were accidentally dropped into water, currentcould flow out of the plastic housing, using the water asthe conducting medium. The water does not short outthe appliance since the exposed surface area of the hotwire connection to the switch terminal offers such ahigh resistance. This limits the current flow to less than1 ma (correct polarity). The fault current is not suffi-cient to trip a 20-amp circuit breaker. To trip the circuitbreaker, there would have to be a line-to-line short thatwould cause an excess of 20 amps (20,000 ma). Should aperson try to retrieve the appliance from the waterwhile it is still plugged into the outlet? In this configu-ration, the fault current would be extremely low (unlessthe switch were in the on position). Since you have noway to tell if the polarity is correct, don’t take chances.NEVER REACH INTO WATER TO RETRIEVE ANAPPLIANCE. Always unplug the appliance first, thenretrieve the appliance and dry it out.

If the appliance is plugged in as shown in figure 9,when the switch is off, voltage will be present through-out all the internal wiring of the appliance. Now if itis dropped into water, the drastically increased “live”surface area will allow a drastic increase in the availableelectric current (I = E/R). A person who accidentallytries to retrieve the dryer would be in a hazardousposition because the voltage in the water could causecurrent to flow through the body (if another part of thebody contacts a ground loop). This illustrates theconcept that reverse polarity is a problem wheneverappliances are used with plastic housings in areas nearsinks, or where the appliance is exposed to rain orwater. Remember, most motorized appliances have airpassages for cooling. Wherever air can go, so canmoisture and water.

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Figure 9

Hair Dryer—Reverse Polarity

If the appliance had a double pole-double throwswitch (DPDT), it would make no difference how theplug was positioned in the outlet. The hazard would beminimized since the energized contact surface would beextremely small. If the appliance were dropped intowater, a high resistance contact in the water and aresulting low available fault current (I = E/R) wouldresult. Later, we will see how GFCIs can be used to pro-tect against shock hazards when using appliances withnonconductive housings around water.

Remember that any electric appliance dropped inwater or accidentally exposed to moisture should beconsidered as energized. The electric power must besafely removed from the appliance before it is retrievedor picked up. You never know if the appliance is pluggedin with the right polarity, without test equipment.Do not take chances. Remove the power first.

Grounding ConceptsGrounding falls into two safety categories. It is

important to distinguish between “system grounding”and “equipment grounding.” Figure 10 illustrates thesetwo grounding components. The difference betweenthese two terms is that system grounding actually con-

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Receptacle

Hair Dryer

Plug

Switch

ServiceEntryPanel(SEP)

“Hot”

“Hot”

Transformer

120 Volt

nects one of the current carrying conductors from thesupply transformer to ground. Equipment groundingconnects or bonds all of the noncurrent-carrying metalsurfaces together and then is connected to ground.

Figure 10

System and Equipment Grounding

System grounding (figure 10) at the transformer pro-vides a grounding point for the power company surgeand lightning protection devices. In conjunction withthe system grounding at the SEP, the voltage acrosssystem components is limited to a safe value shouldthey be subjected to lightning or high voltage surges.The system grounding at the SEP also helps to limithigh voltages from entering the electrical systembeyond the SEP. It is important to check all of the con-nections both indoors and outdoors since many timesthey are exposed to moisture, chemicals, and physicaldamage.

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TransformerSecondary

ServiceEntrance

Primary

GroundedConductor orNeutral

Electrical SymbolFor Ground

System Grounding

EquipmentGroundingConductor

Most Metallic Raceways, Cable Sheaths,and Cable Armor Which Are Continuousand Utilize Proper Fittings May Serve as theEquipment Grounding Conductor. ASeparate Grounding Conductor is NeededWhen Plastic Conduit, Non-metallicSheathed Cable, or Other Wiring MethodsAre Used Which Are Not Approved asGrounding Methods.

Equipment grounding does two things. First, it bondsall noncurrent-carrying metal surfaces together so thatthere will be no potential difference between them.Second, it provides a path for current to flow underground fault conditions. The equipment grounding pathmust have low impedance to ensure rapid operation ofthe circuit overcurrent device should a “hot” to groundfault occur.

Figure 11 depicts some common equipment faultsthat can occur. A problem with the equipment ground-ing system is that under normal conditions it is not acurrent-carrying conductor and a fault would not bereadily detected. Necessary visual inspection will notprovide an operational verification. In figure 11 we cantest the condition of the equipment grounding conductorusing test procedures in this guide. To test the qualityof the branch circuit equipment grounding system, aspecial tester called a ground loop impedance tester isneeded. It is generally recommended that an impedanceof 0.5 ohms be achieved in the equipment grounding

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Figure 11

Equipment Grounding Faults

SERVICEENTRANCE

SOURCE BLACK

WHITE

FAULT

RECEPTACLE

TOOL ORAPPLIANCE

GROUNDING PRONGMISSING

GROUND FAULTCURRENT

WIRE ORCONDUIT

FAULTGROUND

? ?

conductor path. In case of a “hot” to ground fault, thefault current would quickly rise to a value (I = E/R =120/0.5 = 240 amps) necessary to trip a 20 amp fuse orbreaker.

If there is an open or break in the conduit system, asshown in figure 11, a fault in a power tool with a goodgrounding prong would allow the voltage to be placeddirectly on the ungrounded conduit. This would create aserious shock hazard to anyone touching the conduitwith one hand while touching a ground loop with theother. The missing ground prong (with a good conduit orequipment grounding path) would create a seriousshock hazard to the person if the ground loop throughthe feet was low resistance (e.g., wet earth or concreteand wet shoes). It is important to emphasize the needfor low impedance on the equipment grounding loop. Ifthe ground fault current loop in figure 11 were 25 ohmsand the body resistance of the person were 850 ohms,then the 25 ohm ground loop resistance would be toohigh to cause enough circuit breaker current to trip itopen. In this case, the person would then receive multi-ples of current considered deadly (141 ma in this case)through the body, causing death in most instances.Remember that standard circuit breakers are forequipment and fire protection, not people protection.However, ground fault circuit interrupter (GFCI) circuitbreakers are specifically designed for people protection.

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4Branch Circuit andEquipment Testing

Testing Branch Circuit WiringBranch circuit receptacles should be tested periodi-

cally. The frequency of testing should be established onthe basis of outlet usage. In shop areas, quarterly test-ing may be necessary. Office areas may only need annu-al testing. A preventive maintenance program should beestablished. It is not unusual to find outlets as old asthe facility. For some reason, a popular belief exists thatoutlets never wear out. This is false. For example, out-lets take severe abuse from employees disconnectingthe plug from the outlet by yanking on the cord. Thiscan put severe strain on the contacts inside the outletas well as on the plastic face.

The electrical receptacle is a critical electrical systemcomponent. It must provide a secure mechanical con-nection for the appliance plug so that there is a continu-ous electrical circuit for each of the prongs. Receptaclesmust be wired correctly, or serious injuries can resultfrom their use. For this reason, the following two-steptesting procedure is recommended.

Receptacle TestingStep 1

Plug in a three-prong receptacle circuit tester andnote the combination of the indicator lights (see figure12). The tester checks the receptacle for the proper con-nection of the grounding conductor, wiring polarity, andother combinations of wiring errors. If the tester checksthe receptacle as OK, proceed to the next step. If the

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tester indicates a wiring problem, have it corrected assoon as possible. Retest after the problem is corrected.

Figure 12

Receptacle Tester

Step 2

After the outlet has been found to be wired (electri-cally) correct, the receptacle contact tension test mustbe made. A typical tension tester is shown in figure 13.The tension should be eight ounces or more. If it is lessthan eight ounces, have it replaced. The first receptaclefunction that loses its contact tension is usually thegrounding contact circuit. The plug grounding prong isthe last part to leave the receptacle. Because of theleverage (due to its length) it wears out the tension ofthe receptacle contacts quicker than the parallel bladecontacts. Since this is the human safety portion of thegrounding system, it is very important that this contacttension be proper. In determining the frequency of test-ing, the interval must be based on receptacle usage. Allelectrical maintenance personnel should be equippedwith receptacle circuit and tension testers. Other main-tenance employees could also be equipped with testersand taught how to use them. In this manner, the recep-tacles can be tested before maintenance workers usethem. Home receptacles should also be tested.

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Figure 13

Receptacle Tension Tester

Testing Extension CordsNew extension cords should be tested before being put

into service. Many inspectors have found that newextension cords have open ground or reverse polarity. Donot assume that a new extension cord is correct. Test it.

Extension cord testing and maintenance are extreme-ly important. The extension cord takes the electricalenergy from a fixed outlet or source and provides thisenergy at a remote location. The extension cord must bewired correctly or it can become the critical fault path.

Testing of extension cords new and used should usethe same two steps as used in electrical outlet testing.These two steps are:

Step 1

Plug the extension cord into an electrical outlet thathas successfully passed the outlet testing procedure.Plug in any three-prong receptacle circuit tester intothe extension receptacle and note the combination ofindicator lights. If the tester checks the extension cordas OK, proceed to the next step. If the tester indicates afaulty condition, repair or replace the cord. Once theextension cord is correctly repaired and passes thethree-prong circuit tester test, proceed to step 2.

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Step 2

Plug a reliable tension tester into the receptacle end.The parallel receptacle contact tension and the ground-ing contact tension should check out at eight ounces ormore. If the tension is less than eight ounces, the recep-tacle end of the extension cord must be repaired. Aswith fixed electrical outlets, the receptacle end of anextension cord loses its grounding contact tension first.This path is the critical human protection path andmust be both electrically and mechanically in goodcondition.

Testing Plug- and Cord-ConnectedEquipment

The last element of the systems test is the testing ofplug- and cord-connected equipment. The electricalinspector should be on the alert for jury-rigged repairsmade on power tools and appliances. Many times avisual inspection will disclose three-prong plugs withthe grounding prong broken or cut off. In suchinstances, the grounding path to the equipment casehas been destroyed. (The plug can now also be pluggedinto the outlet in the reverse polarity configuration.)

Double insulated equipment generally has a noncon-ductive case and will not be tested using the proceduresdiscussed below. Some manufacturers that have listeddouble insulation ratings may also provide the three-prong plug to ground any exposed noncurrent-carryingmetal parts. In these cases, the grounding path continu-ity can be tested.

A common error from a maintenance standpoint isthe installation of a three-prong plug on a two-conduc-tor cord to the appliance. Obviously, there will be nogrounding path if there are only two conductors in thecord. Some hospital grade plugs have transparent basesthat allow visual inspection of the electrical connection

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to each prong. Even in that situation, you should stillperform an electrical continuity test.

Maintenance shops may have commercial power tooltesting equipment. Many power tool testers require theavailability of electric power. The ohmmeter can be usedin the field and in locations where electric power is notavailable or is not easily obtained. Plug- and cord-con-nected equipment tests are made on de-energized equip-ment. Testing of de-energized equipment in wet anddamp locations can also be done safely.

The plug- and cord-connected equipment test using aself-contained battery-powered ohmmeter is simple andstraightforward. The two-step testing sequence that canbe performed on three-prong plug grounded equipmentfollows:

Step 1—Continuity Test—Ground Pin to Case Test

Set the ohmmeter selector switch to the lowest scale(such as R 1). Zero the meter by touching the two testprobes together and adjusting the meter indicator tozero. Place one test lead (tester probe) on the groundingpin of the de-energized equipment as shown in figure14. While holding that test lead steady, take the othertest lead and make contact with an unpainted surfaceon the metal case of the appliance. You should get areading of less than one ohm. If the grounding path isopen, the meter will indicate infinity. If there is no con-tinuity, then the appliance must be tagged out andremoved from service. If the appliance grounding pathis OK, proceed to step 2.

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Figure 14

Continuity Test

Step 2—Leakage Test—Appliance Leakage Test

Place the ohmmeter selector switch on the highestohm test position (such as R 1,000). Set the meter atzero. Place one test lead on an unpainted surface of theappliance case (see figure 15), then place the other testlead on one of the plug’s parallel blades.

Figure 15

Leakage Test

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Reading 1 ohmor less

R X 1Scale

SPSTSwitch

Tester Probe

White

Green

BlackBrass

Tester Probe

Silver

Metal Case

Reading ∞R X 1,000

Scale

SPSTSwitch

Tester Probe

White

Green

BlackBrass

Tester Probe Silver1.

2.

Metal Case

Observe the reading. The ideal is close to infinity. (Ifa reading of less than one meg-ohm is noted, return theappliance to maintenance for further testing.) With onetest lead still on the case, place the other test lead onthe remaining parallel blade and note the ohmmeterreading. A reading approaching infinity is required.(Again, anything less than one meg-ohm should bechecked by a maintenance shop.)

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5Voltage Detector Testing

OperationWhen you are conducting an electrical inspection, a

voltage detector should be used in conjunction with thecircuit tester, ohmmeter, and tension tester. Severaltypes of these devices are inexpensive and commerciallyavailable.

Figure 16

Voltage Detector

These testers are battery powered and are construct-ed of nonconducting plastic. Lightweight and self-con-tained, these testers make an ideal inspection tool.

The voltage detector works like a radio receiver inthat it can receive or detect the 60 hertz electromagnet-ic signal from the voltage waveform surrounding anungrounded (“hot”) conductor. Figure 17 illustrates thedetector being used to detect the “hot” conductor in acord connected to a portable hand lamp. When the frontof the detector is placed near an energized “hot” orungrounded conductor, the tester will provide an audi-ble as well as a visual warning. In figure 17 if the plugwere disconnected from the receptacle, the detector

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“Green” Power “On” Light

“Red” Warning LightTest Marker

Audible Alarm

Switch

would not sound an alarm since there would not be anyvoltage waveform present.

Figure 17

Testing for “Hot” Conductor

Typical Voltage Detector UsesThe detector can also be used to test for properly

grounded equipment. When the tester is positioned on aproperly grounded power tool (e.g., the electric drill infigure 18), the tester will not sound a warning. The rea-son is that the electromagnetic field is shielded from thedetector so that no signal is picked up. If the groundingprong had been removed and the drill were not ground-ed, the electromagnetic waveform would radiate fromthe drill and the detector would receive the signal andgive off an alarm.

As illustrated in figure 18, the detector can be used totest for many things during an inspection. Receptaclescan be checked for proper AC polarity. Circuit breakerscan be checked to determine if they are on or off. Allfixed equipment can be checked for proper grounding. Ifthe detector gives a warning indication on any equip-ment enclosed by metal, perform further testing with avolt-ohmmeter. Ungrounded equipment can beungrounded or, in addition, there may be a fault to the

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Receptacle

TransformerSEP

“Hot”

“Hot”

120 Volt

enclosure making it “hot” with respect to ground. Anexperienced inspector should use the voltmeter to deter-mine if there is voltage on the enclosure. The voltagedetector should be used as an indicating tester andqualitative testing should be accomplished with othertesting devices such as a volt-ohmmeter. The use of thedetector can speed up the inspection process by allowingyou to check equipment grounding quickly and safely.

Figure 18

Typical Voltage Detector Uses

Voltage versus Detection DistanceAnother unique feature of the voltage detector shown

in figure 18 is that it is voltage sensitive. Figure 19 listsdistances versus voltage at which the detector “red”light will turn on. As an example, a conductor energizedwith 120 volts AC can be expected to be detected fromzero to one inch from the conductor.

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QuicklyCheckCircuitBreakers

Safely and QuicklyCheck for

Voltageat AC Outlets

Easily CheckPower Tools for

Proper Grounding

Check FixedEquipment

Grounding

Figure 19

Voltage vs. Detection Distance

TO DETERMINE APPROXIMATE VOLTAGE:

Slowly approach the circuitry being tested with the front sensor of theunit and observe the distance at which the red LED light glows alongwith the “beep” sound. Use the chart below to determine the approxi-mate voltage in the circuitry.

VOLTAGE (V) 100 200 600 1K 5K 9K

DISTANCE (inch) 0-1 1-2 3-5 15 5 ft 6-7 ft up

These figures may vary due to conditions governing the testing, i.e.,static created by your standing on grounded material, carpets, etc.

The transformer secondary wiring on a furnace auto-matic ignition system rated at 10,000 volts, can beexpected to be detected from six to seven feet away. Youcan use this feature to assist in making judgmentsregarding the degree of hazard and urgency for obtain-ing corrective action.

When you are using the voltage detector, you mustunderstand how it operates to properly interpret itswarning light. If you apply the tester to an energizedpower tool listed as double insulated, you will see thered warning light turn on. In this situation, the voltagewaveform is detected because there is no metal enclo-sure to shield the waveform. The same would occur ifyou were to test in any of the typewriters used inoffices. This does not mean that the plastic or nonmetal-lic enclosed equipment is unsafe, only that it is ener-gized and not a grounding type piece of equipment. Theexamples and explanation of the operational featuresshould be understood fully. Using the detector providesthe opportunity for finding many electrical hazards thatothers may have overlooked.

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6Ground Fault Circuit

Interrupters

Operational TheoryThe ground fault circuit interrupter (GFCI) is a fast-

acting device that monitors the current flow to a protectedload. The GFCI can sense any leakage of current whencurrent returns to the supply transformer by any electri-cal loop other than through the white (grounded conduc-tor) and the black (hot) conductors. When any “leakagecurrent” of five milliamps or over is sensed, the GFCI, in afraction of a second, shuts off the current on both the “hot”and grounded conductors, thereby interrupting the faultcurrent to the appliance and the fault loop.

This is illustrated in figure 20. As long as I1 is equalto I2 (normal appliance operation with no ground faultleakage) the GFCI switching system remains closed. Ifa fault occurs between the metal case of an applianceand the “hot” conductor, fault current I3 will cause an

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Figure 20

Circuit Diagram for a GFCI

GFCI Protection DeviceDifferentialTransformer

Sensing andTest Circuit

EquipmentGrounding

Conductor

InternalEquipmentFault

ExternalGroundFault

“Hot”

Sup

ply

LoadP

rotected

GroundedConductor

N.C.

imbalance (five milliamps or greater for human protec-tion) allowing the GFCI switching system to open (asillustrated) and the removal of power from both thewhite and the “hot” conductors.

Another type of ground fault can occur when a personcomes in contact with a “hot” conductor directly ortouches an appliance with no (or a faulty) equipmentgrounding conductor. In this case I4 represents the faultcurrent loop back to the transformer. This type ofground fault is generally the type that individuals areexposed to.

The GFCI is intended to protect people. It de-ener-gizes a circuit, or portion thereof, in approximately 1/40 ofa second when the ground fault current exceeds fivemilliamps. The GFCI should not be confused withground fault protection (GFP) devices that protectequipment from damaging line-to-ground fault cur-rents. Protection provided by GFCIs is independent ofthe condition of the equipment grounding conductor.The GFCI can protect personnel even when the equip-ment grounding conductor is accidentally damaged andrendered inoperative.

The NEC requires that grounding type receptacles beused as replacements for existing nongrounding types.Where a grounding means does not exist in the recepta-cle enclosure, the NEC allows either a nongrounding orGFCI receptacle. Nongrounding type receptacles arepermitted to be replaced with grounding type recepta-cles when powered through a GFCI.

Remember that a fuse or circuit breaker cannot pro-vide “hot” to ground loop protection at the five mil-liamps level. The fuse or circuit breaker is designed totrip or open the circuit if a line to line or line to groundfault occurs that exceeds the circuit protection devicerating. For a 15 amp circuit breaker, a short in excess of15 amps or 15,000 milliamps would be required. TheGFCI will trip if 0.005 amps or five milliamps start to

39

flow through a ground fault in a circuit it is protecting.This small amount (five milliamps), flowing for theextremely short time required to trip the GFCI, will notelectrocute a person but will shock the person in themagnitude previously noted.

Typical Types of GFCIsGFCIs are available in several different types. Figure

21 illustrates three of the types available (portable, cir-cuit breaker, and receptacle).

Circuit breakers can be purchased with the GFCIprotection built in. These combination types have theadvantage of being secured in the circuit breaker panelto prevent unauthorized persons from having access tothe GFCI. The receptacle type GFCI is the most conve-nient in that it can be tested and/or reset at the locationwhere it is used. It can also be installed so that if it isclosest to the circuit breaker panel, it will provide GFCIprotection to all receptacles on the load side of theGFCI. The portable type can be carried in a mainte-nance person’s tool box for instant use at a work

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Figure 21

Typical Types of GFCIs

Portable Type

Circuit BreakerType

ReceptacleType

location where the available AC power is not GFCI pro-tected. Other versions of GFCIs are available includingmultiple outlet boxes for use by several power tools andfor outdoor applications. A new type is available thatcan be fastened to a person’s belt and carried to the joblocation.

The difference between a regular electrical receptacleand a GFCI receptacle is the presence of the TEST andRESET buttons. The user should follow the manufac-turer’s instructions regarding the testing of the GFCI.Some instructions recommend pushing the TEST but-ton and resetting it monthly. Defective units should bereplaced immediately.

Be aware that a GFCI will not protect the user fromline (hot) to line (grounded conductor) electrical contact.If a person were standing on a surface insulated fromground (e.g., a dry, insulated floor mat) while holding afaulty appliance with a “hot” case in one hand, thenreached with the other hand to unplug an applianceplug that had an exposed grounded (white) conductor, aline to line contact would occur. The GFCI would notprotect the person (since there is no ground loop). Toprevent this type of accident from occurring, it is veryimportant to have an ensured equipment groundingconductor inspection program in addition to a GFCIprogram. GFCIs do not replace an ongoing electri-cal equipment inspection program. GFCIs shouldbe considered as additional protection against the mostcommon form of electrical shock and electrocution: theline (“hot”) to ground fault.

GFCI UsesGFCIs should be used in dairies, breweries, canner-

ies, steam plants, construction sites, and inside metaltanks and boilers. They should be used where workersare exposed to humid or wet conditions and may comein contact with ground or grounded equipment. They

41

should be used in any work environment which is or canbecome wet and in other areas that are highly grounded.

Nuisance GFCI TrippingWhen GFCIs are used in construction activities,

the GFCI should be located as close as possible to theelectrical equipment it protects. Excessive lengths ofelectrical temporary wiring or long extension cords cancause ground fault leakage current to flow by capacitiveand inductive coupling. The combined leakage currentcan exceed five milliamps causing the GFCI to trip—“nuisance tripping.” GFCIs are now available that canbe fastened to your belt. You can plug the extensioncord into the GFCI and use the protected duplex topower lighting and power tools. This is the ideal GFCIfor construction and maintenance workers. It alsoallows the GFCI to be near the user location, therebyreducing nuisance trips.

Other nuisance tripping may be caused by:

• Outdoor GFCIs not protected from rain or water• Bad electrical equipment with case to hot conduc-

tor fault• Too many power tools on one GFCI branch• Resistive heaters• Coiled extension cords (long lengths)• Poorly installed GFCI• Electromagnetic induced current near high voltage

lines• Portable GFCI plugged into a GFCI protected

branch circuit

Remember that a GFCI does not prevent shock.It limits the duration of the shock so that theheart does not go into ventricular fibrillation.The shock lasts about 1/40 of a second and can beintense enough to knock a person off a ladder orotherwise cause an accidental injury. Also,

42

remember that the GFCI does not protect againstline-to-line shock. Be sure to check insulation andconnections on power tools each time before use.

43

7Common Electrical

DeficienciesTable A offers a list of frequently violated standards

regarding electricity. Items in table A should become apart of any electrical inspection checklist. Table A cross-references the National Electrical Code (1996 edition) andOSHA (Occupational Safety and Health Act) standards.

Table A

Frequently Violated Electrical StandardsNEC OSHA OSHA

70-1996 29 CFR 1910 29 CFR 1926Reference Subject Standard Standard110-3 Suitability for safe installation .303(b)(1)(i) .403(b)(1)(i)110-12(a) Unused openings—cabinets/ .305(b)(1) .405(b)(1)

boxes110-13(a) Secure mounting of equipment .303(b)(1)(ii) .403(b)(1)(ii)110-14(a) Electrical terminal connections .303(b)(1)(i) .403(b)(1)(i)110-14(b) Electrical splices .303(c) .403(e)110-16 Working space about equipment .303(g)(1) .403(i)(1)110-17 Guarding live parts .303(g)(2) .403(i)(2)110-22 Disconnect and circuit .303(f) .403(h)

identification200-11 Reverse polarity .304(a)(2) .404(a)(2)210-7 Receptacles, cords, and plugs .305(j)(2)(i) .405(j)(2)(i)210-8 Ground fault circuit interrupters .303(b)(1)(vii) .404(b)(1)(ii)210-63 Maintenance worker receptacles .303(b)(1)(vii)250-42 Grounding fixed equipment .304(f)(5)(iv) .404(f)(7)(iii)250-45 Grounding cord and plug .304(f)(5)(v) .404(f)(7)(iv)

equipment250-51 Effective grounding .304(f)(4) .404(f)(6)250-59 Grounding cord-connected

equipment400-7 Flexible cord and cable uses .305(g)(1)(i) .405(g)(1)(i)400-8 Flexible cord and cable .305(g)(1)(iii) .405(g)(1)(iii)

not permitted400-9 Flexible cord and cable splices .305(g)(2)(iii) .405(g)(2)(iii)400-10 Pull at joints and terminals .305(g)(2)(iii) .405(g)(2)(iv)410-57 Receptacles—damp/wet locations .305(i)(2)(ii) .405(j)(2)(ii)430-101 Motor disconnect means .305(j)(4)(ii) .405(j)(4)(ii)

44

NEC 110-3—29 CFR 1910.303(b)(1)—Examination,Identification, Installation, and Use of Equipment.Operational characteristics to provide practical employ-ee and facility safeguarding are provided. Suitability,mechanical strength of enclosures, connection space,insulation, heating and wiring effects, proper use of list-ed or labeled equipment, and any other factor thatwould provide personnel safeguarding should be evalu-ated. Fabricating and using extension cords with junc-tion box receptacle ends would be a violation of thisstandard.

NEC 110-12(a)—29 CFR 1910.305(b)(1)—UnusedOpenings. This reference requires that electrical equip-ment be installed in a neat and professional manner. Allopenings in junction boxes and electrical equipment mustbe effectively closed to prevent metal objects from enter-ing the enclosure and causing arcing or shorting of thesupply conductors. Protection for personnel is also pro-vided by preventing contact with electrically live parts.

NEC 110-13(a)—Secure Mounting of Equipment.Affixed electrical equipment must be firmly secured tothe surface on which it is mounted. You may havenoticed a conduit that is hanging loose or equipmentboxes that are not secured to the wall. These are exam-ples of violations of this standard.

NEC 110-14(a)—Electrical Terminal Connections.Loose or improperly tightened terminal connectionshave been determined as the cause of many electricalfires and equipment burnouts. Be alert to this problemwhen intermittent equipment operation or flickeringlights are observed.

NEC 110-14(b)—29 CFR 1910.303(c)—Splices. Splicesare required to be joined by suitable splicing devices ormethods. The three elements of a proper splice are (1)mechanical strength, (2) electrical conductivity, and (3)insulation quality. These factors must be at least equiv-

45

alent to the conductors being spliced.

NEC 110-16—29 CFR 1910.303(g)(1)—Working Spaceabout Electrical Equipment (600 volts, nominal, or less).This paragraph requires that sufficient access andworking space be provided and maintained about allelectric equipment. The electrical equipment clearancespace must not become storage space. It maybe neces-sary to make the clearance space obvious by using floorstripes or other methods.

NEC 110-17—29 CFR 1910.303(g)(2)—Guarding ofLive Parts (600 volts, nominal, or less). This referencerequires that the live parts of electric equipment oper-ating at 50 volts or more shall be guarded against acci-dental contact. Approved enclosures are recommended.When the alternative of location (e.g., eight-foot eleva-tion above the floor) is used, employee safeguardingshould be carefully evaluated.

NEC 110-22—29 CFR 1910.303(f)—Identification ofDisconnecting Means. This reference requires that thedisconnecting means for motors and appliances, and eachservice, feeder, or branch circuit at the point where itoriginates be legibly marked to indicate its purposeunless located and arranged so the purpose is evident.Many times a contractor will install new wiring andleave circuit breaker panels with blank circuit identifica-tion cards. Whenever electrical modifications are com-pleted, the circuit identification cards should be updated.

NEC 200-11—29 CFR 1910.304(a)(2)—Polarity ofConnections. No grounded conductor shall be attachedto any terminal or lead so as to reverse designatedpolarity. This can usually be determined by using thethree-prong circuit tester. Be sure to test not only wallreceptacles but extension cord receptacles as well.

NEC 210-7 & 410-58—29 CFR 1910.305(j)(2)(i)—Grounding Type Receptacles, Cord Connectors, andAttachment Plugs. These references require that recep-

46

tacles installed on 15 and 20 ampere branch circuits beof the grounding type. Grounding type attachmentplugs and mating cord connectors must also be used onelectrical equipment where grounding type receptaclesare provided. An exception would be the use of listeddouble insulated tools or appliances.

NEC 210-8—Ground Fault Circuit InterrupterProtection (GFCI) for Personnel. Whereas this sectionapplies to dwelling units, hotels, and motels, be remind-ed that GFCI protection may be provided for other cir-cuits, locations, and occupancies where personnel canbe protected against line to ground shock hazards.GFCI protection requirements for other specific applica-tions are NEC: 305-6—construction sites; 427-26—fixedheating for pipelines; 426-31—fixed outdoor deicingequipment; 511-10—commercial garages; 551-41(c)—recreational vehicles; and 680—swimming pools, tubs,and fountains. The various codes and regulations areminimal requirements and in many cases are notretroactive. From an accident prevention standpoint,you should look for areas where potential line to groundshock hazards could occur and recommend GFCI protec-tion regardless of the lack of retroactive need.

NEC 210-63—Heating, Air-Conditioning, andRefrigeration Equipment Outlet. It is now a NECrequirement that a 125 volt, single phase, 15 or 20ampere receptacle be installed at an accessible locationand on the same level as equipment located on rooftops, in crawl spaces, and in attic spaces, for use bymaintenance personnel for servicing equipment. Thesereceptacles must be on the same level and within 25feet of the equipment. Provide GFCI protected recepta-cles if the maintenance work must be accomplished inwet conditions or in bathrooms or on roof tops.

NEC 250-42—29 CFR 1910.304(f)(5)(iv)—GroundingFixed Equipment—General. This paragraph requires

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exposed noncurrent-carrying metal parts of fixed equip-ment to be grounded. By using the noncontact voltagedetector, you can quickly determine whether the equip-ment metal housing is properly grounded.

NEC 250-45—29 CFR 1910-304(f)(5)(iv)—Groundingof Cord- and Plug-Connected Equipment. This para-graph requires that exposed noncurrent-carrying metalparts of cord- and plug- connected equipment begrounded. Exceptions to this requirement are tools andappliances that are listed as double insulated or thatare supplied through an isolating transformer with anungrounded secondary of not over 50 volts.

NEC 250-51—Effective Grounding Path. The path toground from circuits, equipment, and conductor enclo-sure shall: (1) be permanent and continuous, (2) havecapacity to conduct safely any fault current likely to beimposed on it, and (3) have sufficiently low impedanceto limit the voltage to ground and to facilitate the oper-ation of the circuit protective devices. If a portablepower tool had the equipment grounding prong brokenoff, the NEC 250-51(1) requirement would not be metsince the grounding path would not be continuous.Extension cords being used with defects in the equip-ment grounding conductor path would also not meetthis requirement. If the grounding path test result wasmore than 10 ohms, NEC 250-51(3) would not be met. Itis recommended that the equipment grounding conduc-tor loop impedance be less than 0.5 ohm, and this canonly be determined by use of a ground loop impedancetester.

NEC 250-59—Cord- and Plug-Connected Equipment.This section describes three methods that can be usedto ground equipment effectively. One method is the useof the metal enclosure of the conductors supplying suchequipment when used with approved connectors andreceptacles. The second method is by means of theequipment grounding connector run with the power

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supply conductors in a cable assembly or flexible cord.The third method is by means of a separate flexible wireor cable. The main purpose of alternative methods is toensure that all metal enclosures and frames are bondedtogether at the same ground potential.

NEC 400-7—29 CFR 1910.305(g)(1)(i)—Flexible Cordand Cable Uses Permitted. Specific applications whereflexible cords and cables are permitted include pen-dants, wiring of fixtures, portable lamps, appliances,and stationary equipment that may have to be movedfrequently for maintenance or other purposes. Anotherimportant use is the prevention of the transmission ofnoise and vibration. Special attention should be given tothe proper installation and protection of flexible cordsand cables.

NEC 400-8—29 CFR 1910.305(g)(1)(iii)—FlexibleCord and Cable Uses Not Permitted. Flexible cordsmust not be used as a substitute for fixed wiring.Additionally, they must not be run through holes inwalls, ceilings or floors, or doorways or windows.

NEC 400-9—29 CFR 1910.305(g)(2)(ii)—Splices. Thissection prohibits the use of flexible cords that have beenspliced or tapped. The repair by splicing of hard servicecord No. 14 or larger is permitted if done in accordancewith NEC 110-14(b).

NEC 400-10—29 CFR 1910.305(g)(2)(iii)—Pull atJoints and Terminals. This reference requires that flexi-ble cords be connected to devices and fittings so thattension will not be transmitted to joints or terminals.This requirement is applicable to the connection of thecord to the appliance as well as the attachment plug.

NEC 410-57—29 CFR 1910.305(j)(2)(ii)—Receptaclesin Damp and Wet Locations. A receptacle installed out-doors in a location where it is protected from the weath-er, such as under a roof, is required to be in an enclosurethat is weatherproof only when an attachment plug is

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not plugged in. In areas where the receptacle is exposedto outdoor weather (unprotected) or other wet locations(e.g., an equipment water washing or steam cleaningarea) the receptacle and attachment plug must be aweatherproof combination except in instances where thereceptacle is used for portable tools and equipment nor-mally connected to the receptacle only when attended.

NEC 430-101—29 CFR 1910.305(j)(4)(ii)—MotorDisconnecting Means. This section requires that electri-cal motor-driven equipment have a disconnectingmeans capable of disconnecting motors and controllersfrom the circuit. For motor branch circuits under 600volts, the disconnecting means must be located in sightfrom the controller location. Consideration must also begiven to using disconnects that are designed to accept alockout device.

The above list is not comprehensive. It identifiessome of the most common electrical safety problemareas. Testing methods in part 4 of this guide will helpyou document many electrical hazards.

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8Inspection

Guidelines/ChecklistBefore you conduct an electrical inspection, check

your test equipment to be sure it is in proper workingorder. You should have a circuit tester, a GFCI tester(there are combination circuit/GFCI testers available), acontact tension tester, and a volt-ohmmeter. Removejewelry, watches, and other metal objects. Footwearshould have synthetic soles (do not wear leather soles).A clipboard, writing material, and the checklist in tableB should also be included. A camera is optional, but ifused, before-and-after photos/slides will make valuablevisual training aids. Table B provides general guide-lines that will assist you in checking for electrical haz-ards from the service entrance panel(s) to the equip-ment using the power.

Table B

Inspection Guidelines

1. Service Entrance Panel—Circuit I.D., Secure Mounting,Knockouts, Connectors, Clearances, Live Parts, Ratings

2. System Grounding—Secure Connections, Corrosion, Access,Protection, Wire Size

3. Wiring—Temporary, Splices, Protected, Box Covers, Openings,Insulation, Fittings, Workmanship

4. Electrical Equipment/Machinery—Grounding, Wire Size,Overcurrent and Disconnects, Installation, Protection

5. Small Power Tools—Attachment Plugs, Cords, Clamps,Leakage, Grounding, Splices

6. Receptacles—Polarity, Adequate Number, Mounting, Covers,Grounding, Tension, Connections, Protection

7. Lighting—Grounding, Connections, Plugs and Cords, CordClamps, Live Parts

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8. GFCI Protection—Bathrooms, Crawl Spaces, Basements, WetLocations, Outdoors, Garages, Pools/Tubs, Testing

Inspector_________________________________________________

Date ____________________________________________________

Further explanation of these guidelines is as follows:

1. Service Entrance Panel—Check the branch cir-cuit identification. It should be up to date andposted on the panel door. Be sure the panel andcable or conduit connectors are secure. Thereshould be no storage within three feet of the panel.No flammable materials of any kind should bestored in the same area or room. Look for corro-sion and water in or around the area. Missingknockouts, covers, or openings must be coveredproperly to eliminate exposure to live parts.

2. System Grounding—Check connection of thegrounding electrode conductor to the metal coldwater pipe and to any driven ground rod. Alsocheck any bonding jumper connections and anysupplemental grounding electrode fittings. Theseitems should not be exposed to corrosion andshould be accessible for maintenance and visualinspection.

3. Wiring (General)—Temporary wiring that isbeing used on a permanent basis should bereplaced with fixed wiring. Conduit and/or cablesystems must be protected from damage by vehi-cles or other mobile equipment. All fittings andconnections to junction boxes and other equipmentmust be secure. No exposed wiring can be allowed.Check for missing knockouts and cover plates.Jury-rigged splices on flexible cords and cablesshould be correctly repaired. Electrical equipmentshould be installed in a neat and professionalmanner. Check for damaged insulation on flexiblecord and pendant drop cords.

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4. Electrical Equipment/Machinery—Test forproper grounding. All electrical equipment andmachinery must be grounded effectively so thatthere is no potential difference between the metalenclosures. Use the voltage detector to find dis-crepancies and other test equipment to determinethe corrective action required. Disconnects shouldbe easily identified with the specific machinerythey shut off. Disconnects should also be accessiblenear the machinery for use in an emergency. Thedisconnects should be activated periodically to besure they are operable. All electrical connectionsto the equipment must be secure so that no cord orcable tension will be transmitted to the electricalterminals within the equipment. The wiringinstallation should be such that it is protectedfrom damage at all times.

5. Small Power Tools—Attachment plugs shouldbe checked for defective cord clamps and broken ormissing blades. Connection of the cord to thepower tool should be secure. Use your ohmmeterto check for leakage and for an effective equipmentgrounding conductor.

6. Receptacles—The receptacles should be testedfor proper wiring configuration. There should beenough receptacles installed to eliminate, asmuch as possible, the use of extension cords.Covers should be in place and not broken.Multiple outlet adapters on a single outlet shouldbe discouraged to prevent overloading. Surfacemounted receptacle boxes should be protectedfrom damage by mobile or motorized equipment.

7. Lighting—Cord- and plug-connected metal lampsand fixtures should be tested for grounding. Checkall cord clamps for secure connections. Frayed orold cords should be replaced.

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8. GFCI Protection—Generally, GFCI protection isnot required by the NEC on a retroactive basis.Where there is an employee exposure to potentialline to ground shock hazards, GFCI protectionshould be provided. This is especially important inwork areas where portable electrical equipment isbeing used in wet or damp areas in contact withearth or grounded conductive surfaces. Use yourGFCI tester to be sure that the GFCI is operable.After years of service, GFCIs can become defectiveand need to be replaced. Receptacles receivingGFCI protection should be labeled to inform ofthat fact.

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9Safety Program Policy and

Procedures

PolicyEach facility should have an electrical safety program

policy. The policy should cover the responsibilities of allemployees including supervisors, employees, and thespecialists who inspect, install, and maintain the elec-trical systems and equipment. The policy should stressmanagement’s concern and support. Individuals whoare responsible for applying and enforcing the electricalpolicy should have standards of performance thatinclude periodic assessment of their electrical safetyperformance.

In addition to policy and implementation procedures,the electrical safety program should include four basicareas of concern, which are: training and education;hazardous condition reporting; work practices; andhousekeeping.

The professionals responsible for installing, repair-ing, and maintaining electrical equipment and systemsshould be familiar with NFPA 70E, Electrical SafetyRequirements for Employee Workplaces. Managementshould support an effective preventive maintenanceprogram. Use NFPA 70B, Electrical EquipmentMaintenance, as a guide to implement or refine thistype of program. Suggestions for improving any electri-cal safety program should include the items in this sec-tion. All employees must be responsible for being awareof and reporting unsafe electrical equipment.Discussion in the next section offers suggestions forensuring that these responsibilities are carried outeffectively.

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Policy and the Safety-Related Work PracticesStandard

Policy regarding training must encompass all applic-able features of the OSHA Safety-Related WorkPractices Standard—29 CFR 1910.331-335. Thatstandard:

• 1910.332—requires training for both “qualified”and “unqualified” persons (defined by the stan-dard) who work on, near, or with electrical hazards(defined by the standard)

• 1910.332—lists typical occupational categories ofemployees for which training is required

• 1910.332—includes additional training require-ments for qualified persons

• 1910.333—provides lockout/tagout requirementsfor electrical conductors and equipment in electri-cal utilization installations and thus extends pro-tections of the lockout/tagout standard (29 CFR1910.147) to electrical workers

• 1910.333—includes acceptable practices for per-forming specific types of work as a qualified andunqualified person (requirements address, amongother things: energized equipment; overhead lines;illumination; confined or enclosed work spaces;conductive materials and equipment; portable lad-ders; conductive apparel; housekeeping duties; andinterlocks)

• 1910.334—addresses portable electric equipmentincluding, among other things, requirements for:handling practices; visual inspection; conductivework locations; attachment plugs and circuits (andcircuit testing, which only qualified persons mayperform)

• 1910.335—personal protective equipment

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Supervisory ResponsibilitiesTraining and Education

Supervisors should be trained to assist in dischargingthe electrical safety program responsibilities for theirspecific areas. If employees under their supervision use,install, repair, or modify electrical equipment and/orappliances, the supervisor must ensure that they havereceived the proper training. The supervisor should alsomonitor employees and assess their performanceagainst the established facility safety program policy.

Hazardous Condition Reporting

A written procedure promoting the observation andreporting of electrical hazards should be implemented.An employee recognition program should also be includ-ed in conjunction with the hazard reporting program.That will recognize employees who help locate electricalhazards and help ensure that hazards are eliminated ina timely manner.

Work Practices

The supervisor must ensure that employees followsafe work practices. A sample of suggested work prac-tices is included in this section under EmployeeResponsibilities. Employees should be rated on theirperformance in following safe work practices. Thesupervisor should also be familiar with OSHA andOSHANC (Occupational Safety and Health Act of NorthCarolina) standards as they apply to the workplaceunder his or her responsibility.

Housekeeping

Floor area problems always present challenges to thesupervisor. Areas around electrical equipment, such ascircuit breaker panels, disconnects, and fixed powertools, should be kept free from stored items, debris, andany liquids or material that would create slippery floors

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or obstruct access to the equipment for maintenance oremergencies. When hazards of this nature are reportedto the supervisor, they should be recorded and neces-sary work orders should be issued for corrective action.

Employee ResponsibilitiesTraining and Education

Employees should be trained in electrical safety workpractices and equipment operation. Any changes in jobduties will require additional safety training. Manyaccidents are caused when employees lack knowledge ofthe equipment or its operation. Sometimes employeesare blamed for accidents when, in reality, specific train-ing was not provided for the employees.

Hazardous Condition Reporting

Employees should always report unsafe equipment,conditions, or procedures. Repairing equipment shouldreceive top priority, even if that means rescheduling aprocess or project. Under no condition should defectiveelectrical equipment causing electrical shock be used.The electrical safety policy should be followed, and devi-ations should be reported immediately.

Work Practices

Employees are responsible for following their employ-er’s safe work practices, procedures, and policy. Eachemployee should also be familiar with OSHA regula-tions as they apply to workplace safety.

Housekeeping

In the process of performing their work, employeesshould remain observant and report conditions thatcould cause any type of accident. Good housekeepingrequires all employees to observe activities that couldcause electrical shock hazards. Using electrical equip-ment that is not properly grounded in areas that have

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water on the floor can create shock hazards. Storingtools or other materials around electrical panels orequipment disconnects can create hazards for others, aswell as prevent immediate access to electrical equip-ment for disconnection in an emergency. Cleaning toolsand electrical equipment with solvents can createhealth and physical safety problems. Discarding ragscontaining solvents into trash receptacles can createfire hazards as well.

Electrical Safety PolicySupervisors must know all facets of their employer’s

electrical safety policy and ensure that their employeesalso know and follow these policies. As a minimum, thefollowing items should be included in the electrical safe-ty policy:

• Power equipment should be plugged into wallreceptacles with power switches in the off position.

• Electrical equipment should be unplugged bygrasping the plug and pulling. Never pull or jerkthe cord to unplug the equipment.

• Frayed, cracked, or exposed wiring on equipmentcords must be corrected. Also check for defectivecord clamps at locations where the power cordenters the equipment or the attachment plug.

• “Cheater plugs,” extension cords with junction boxreceptacle ends, or other jury-rigged equipmentshould not be used.

• Temporary or permanent storage of materialsmust not be allowed within three feet of anelectrical panel or electrical equipment.

• Any electrical equipment causing shocks or whichhas high leakage potential must be tagged with aDANGER—DO NOT USE label or equivalent.

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The following industry guides are available from the N.C. Depart-ment of Labor’s Division of Occupational Safety and Health:1#1. A Guide to Safety in Confined Spaces1#2. A Guide to Procedures of the Safety and Health Review Board of North

Carolina1#3. A Guide to Machine Safeguarding1#4. A Guide to OSHA in North Carolina1#5. A Guide for Persons Employed in Cotton Dust Environments1#6. A Guide to Lead Exposure in the Construction Industry1#7. A Guide to Bloodborne Pathogens in the Workplace1#8. A Guide to Voluntary Training and Training Requirements in OSHA

Standards1#9. A Guide to Ergonomics#10. A Guide to Farm Safety and Health#11. A Guide to Radio Frequency Hazards With Electric Detonators#12. A Guide to Forklift Operator Training#13. A Guide to the Safe Storage of Explosive Materials#14. A Guide to the OSHA Excavations Standard#15. A Guide to Developing and Maintaining an Effective Hearing

Conservation Program#17. A Guide to Asbestos for Industry#18. A Guide to Electrical Safety#19. A Guide to Occupational Exposure to Wood and Wood Dust#20. A Guide to Crane Safety#21. A Guide to School Safety and Health#23. A Guide to Working With Electricity#25. A Guide to Personal Protective Equipment#26. A Guide to Manual Materials Handling and Back Safety#27. A Guide to the Control of Hazardous Energy (Lockout/Tagout)#28. A Guide to Eye Wash and Safety Shower Facilities#29. A Guide to Safety and Health in Feed and Grain Mills#30. A Guide to Working With Corrosive Substances#31. A Guide to Formaldehyde#32. A Guide to Fall Prevention in Industry#33. A Guide to Office Safety and Health#34. A Guide to Safety and Health in the Poultry Industry#35. A Guide to Preventing Heat Stress#36. A Guide to the Safe Use of Escalators and Elevators#37. A Guide to Boilers and Pressure Vessels#38. A Guide to Safe Scaffolding#39. A Guide to Safety in the Textile Industry#40. A Guide to Emergency Action Planning#41. A Guide to OSHA for Small Businesses in North Carolina

Occupational Safety and Health (OSH)Sources of Information

You may call 1-800-NC-LABOR to reach any division of the N.C.Department of Labor; or visit the NCDOL home page on the World WideWeb, Internet Web site address: http://www.nclabor.com.N.C. Division of Occupational Safety and Health

Mailing Address: Physical Location:4 W. Edenton St. 111 Hillsborough St.Raleigh, NC 27601-1092 (Old Revenue Building, 3rd Floor)Local Telephone: (919) 807-2900 Fax: (919) 807-2856

For information concerning education, training and interpretations of occupationalsafety and health standards contact:Bureau of Education, Training and Technical Assistance

Mailing Address: Physical Location:4 W. Edenton St. 111 Hillsborough St.Raleigh, NC 27601-1092 (Old Revenue Building, 4th Floor)Telephone: (919) 807-2875 Fax: (919) 807-2876

For information concerning occupational safety and health consultative servicesand safety awards programs contact:Bureau of Consultative Services

Mailing Address: Physical Location:4 W. Edenton St. 111 Hillsborough St.Raleigh, NC 27601-1092 (Old Revenue Building, 3rd Floor)Telephone: (919) 807-2899 Fax: (919) 807-2902

For information concerning migrant housing inspections and other related activi-ties contact:Agricultural Safety and Health Bureau

Mailing Address: Physical Location:4 W. Edenton St. 111 Hillsborough St.Raleigh, NC 27601-1092 (Old Revenue Building, 2nd Floor)Telephone: (919) 807-2923 Fax: (919) 807-2924

For information concerning occupational safety and health compliance contact:Safety and Health Compliance District Offices

Raleigh District OfficeTelephone: Safety (919) 662-4597 Fax: (919) 662-4709

Health (919) 662-4711Charlotte District Office(901 Blairhill Road, Suite 200, Charlotte, NC 28217-1578)Telephone: Safety (704) 342-6163 Fax: (704) 342-5919Winston-Salem District Office(901 Peters Creek Parkway, Winston-Salem, NC 27103-4551)Telephone: Safety (336) 761-2700 Fax: (336) 761-2326

Health (336) 761-2700 Fax: (336) 761-2130Wilmington District Office(1200 N. 23rd St., Suite 205, Wilmington, NC 28405-1824)Telephone: (910) 251-2678 Fax: (910) 251-2654Asheville District Office(204 Charlotte Highway, Suite B, Asheville, NC 28803-8681)Telephone: (828) 299-8232 Fax: (828) 299-8266

***To make an OSHA Complaint, OSH Complaint Desk: (919) 807-2796***For statistical information concerning program activities contact:Planning, Statistics and Information Management

Mailing Address: Physical Location:4 W. Edenton St. 111 Hillsborough St.Raleigh, NC 27601-1092 (Old Revenue Building, 2nd Floor)Telephone: (919) 807-2950 Fax: (919) 807-2951

For information about books, periodicals, vertical files, videos, films, audio/slidesets and computer databases contact:N.C. Department of Labor Library

Mailing Address: Physical Location:4 W. Edenton St. 111 Hillsborough St.Raleigh, NC 27601-1092 (Old Revenue Building, 5th Floor)Telephone: (919) 807-2848 Fax: (919) 807-2849

N.C. Department of Labor (Other than OSH)4 W. Edenton St.Raleigh, NC 27601-1092Telephone: (919) 733-7166 Fax: (919) 733-6197

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