When Is Wire Size An Electrical Hazard?
How Practice You Control Hazards?
In guild to control hazards, you must first create a safe work environment, then piece of work in a safety fashion. Generally, information technology is best to remove the hazards altogether and create an surroundings that is truly safe. When OSHA regulations and the NEC are followed, safety work environments are created.
But, you never know when materials or equipment might neglect. Set up yourself for the unexpected by using safe piece of work practices. Use as many safeguards as possible. If one fails, another may protect yous from injury or death.
A safe work environment is created by controlling contact with electrical voltages and the currents they can cause. Electric currents demand to exist controlled so they do not pass through the torso. In addition to preventing shocks, a safety work environment reduces the take a chance of fires, burns, and falls. You need to guard against contact with electrical voltages and control electrical currents in order to create a safe work environment. Brand your environment safer by doing the following:
- Care for all conductors—fifty-fifty "de-energized" ones—as if they are energized until they are locked out and tagged.
- Lock out and tag out circuits and machines.
- Prevent overloaded wiring by using the right size and type of wire.
- Preclude exposure to live electrical parts by isolating them.
- Prevent exposure to live wires and parts by using insulation.
- Foreclose shocking currents from electrical systems and tools by grounding them.
- Foreclose shocking currents by using GFCI's.
- Prevent also much electric current in circuits by using overcurrent protection devices.
electricians to climb on tiptop of the booth and piece of work from in a higher place. The top of the booth was filled with pipes and ducts that restricted visibility and movement. Flashlights were required.
The electricians started at opposite ends of the booth. 1 electrician saw a flash of lite, but continued to work for nigh v minutes, then climbed down for some wire. While cutting the wire, he smelled a called-for odor and called to the other electrician. When no i answered, he climbed back on superlative of the booth. He institute his co-worker in contact with a single-strand wire from one of the lights. Needle-nose wire strippers were stuck in the left side of the victim's chest. Apparently, he had been stripping insulation from an improperly grounded 530-volt, single-strand wire when he contacted it with the stripper. In this instance, the electricians knew they were working on energized circuits. The breakers in the booth'due south control panel were not labeled and the lock used for lock-out/tag-out was broken. The surviving electrician stated that locating the means to de-energize a circuit often takes more than time than the actual chore.
The electrician would be alive today if the following rules had been observed.
- Ever close off circuits—then exam to ostend that they are de-energized—before starting a job.
- Switchgear that shuts off a circuit must be conspicuously labeled and like shooting fish in a barrel to access.
- Lock-out/tag-out materials must ever exist provided, and lock-out/tag-out procedures must always exist followed
Create a condom piece of work environment by locking out and tagging out circuits and machines. Earlier working on a circuit, you must turn off the power supply. Once the circuit has been shut off and
de-energized, lock out the switchgear to the excursion so the power cannot be turned back on inadvertently. Then, tag out the circuit with an easy-to-run across sign or label that lets everyone know that you are working on the circuit. If y'all are working on or near machinery, you must lock out and tag out the machinery to prevent startup. Before you begin piece of work, you lot must test the excursion to make sure it is de-energized.
Lock-out/tag-out is an essential safe procedure that protects workers from injury while working on or about electric circuits and equipment. Lock-out involves applying a physical lock to the ability source(south) of circuits and equipment after they have been shut off and de-energized. The source is then tagged out with an piece of cake-to-read tag that alerts other workers in the expanse that a lock has been practical.
In improver to protecting workers from electrical hazards, lock-out/tag-out prevents contact
with operating equipment parts: blades, gears, shafts, presses, etc.
A worker was replacing a V-chugalug on a dust collector blower. Before offset work, he shut down the unit at the local switch. Withal, an operator in the control room restarted the unit using a remote switch. The worker's paw was caught between the caster and belts of the blower, resulting in cuts and a fractured finger.
When performing lock-out/tag-out on mechanism, you must always lock out and tag out ALL free energy sources leading to the mechanism.
Also, lock-out/tag-out prevents the unexpected release of hazardous gasses, fluids, or solid matter in areas where workers are present.
An employee was cut into a metal pipe using a blowtorch. Diesel fuel was mistakenly discharged into the line and was ignited by his torch. The worker burned to decease at the scene.
All valves along the line should have been locked out, blanked out, and tagged out to foreclose the release of fuel. Blanking is the process of inserting a metal disk into the space between two pipe flanges. The disk, or bare, is then bolted in place to prevent passage of liquids or gasses through the piping.
When performing lock-out/tag-out on circuits and equipment, yous tin can utilise the checklist below.
- Identify all sources of electrical energy for the equipment or circuits in question.
- Disable backup free energy sources such as generators and batteries.
- Identify all close-offs for each energy source.
- Notify all personnel that equipment and circuitry must be shut off, locked out, and tagged out. (Simply turning a switch off is Not enough.)
- Shut off energy sources and lock switchgear in the OFF position. Each worker should apply his or her private lock. Do non give your primal to anyone.
- Exam equipment and circuitry to make sure they are de-energized. This must be done by a qualified person.*
- Deplete stored free energy by bleeding, blocking, grounding, etc.
- Apply a tag to alert other workers that an energy source or piece of equipment has been locked out.
- Make sure anybody is safe and accounted for before equipment and circuits are unlocked
and turned back on. Annotation that simply a qualified person may determine when it is safe to re-energize circuits.
*OSHA defines a "qualified person" as someone who has
received mandated training on the hazards and on the
structure and operation of equipment involved in a task.
Electrical hazards result from using the incorrect size or type of wire. You must control such hazards to create a safe work environment. You must cull the right size wire for the amount of current
expected in a circuit. The wire must be able to handle the current safely. The wire's insulation must be appropriate for the voltage and tough plenty for the environment. Connections need to be reliable and protected.
| Use the right size and blazon of wire. |
| AWG—American Due westire Gauge—a measure of wire size |
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| Wires come in different sizes. The maximum current each size can conduct safely is shown. |
The wiring methods and size of conductors used in a arrangement depend on several factors:
- Intended employ of the circuit system
- Building materials
- Size and distribution of electrical load
- Location of equipment (such as underground burying)
- Ecology weather (such as dampness)
- Presence of corrosives
- Temperature extremes
Stock-still, permanent wiring is better than extension cords, which tin can be misused and damaged more easily. NEC requirements for fixed wiring should always be followed. A variety of materials can be used in wiring applications, including nonmetallic sheathed cable (Romex®), armored cable, and metal and plastic conduit. The choice of wiring material depends on the wiring environment and the need to back up and protect wires.
Aluminum wire and connections should be handled with special care. Connections made with aluminum wire can loosen due to oestrus expansion and oxidize if they are not made properly. Loose or oxidized connections can create heat or arcing. Special clamps and terminals are necessary to brand proper connections using aluminum wire. Antioxidant paste can exist practical to connections to prevent oxidation.
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| Nonmetalic capsule helps protect wires from harm. |
Use flexible wiring properly
Electric cords supplement fixed wiring past providing the flexibility required for maintenance, portability, isolation from vibration, and emergency and temporary power needs.
Flexible wiring tin can be used for extension cords or power supply cords. Ability supply cords tin can be removable or permanently attached to the appliance.
An investigation showed that the female cease of the extension cord was broken. The spring, embrace plate, and part of the casing were missing from the face of the female connector. Likewise, the grounding prong on the welder's power cord plug was and then severely bent that it slipped outside of the connection. Therefore, the arc welder was non grounded. Normally, it would have been impossible to insert the plug incorrectly. But, since the cord'due south female end was damaged, the "bad" connexion was able to occur.
Do not let this happen to yous. Use these safe practices:
- Thoroughly inspect all electrical equipment before start work.
- Practise non apply extension cords every bit a substitute for fixed wiring. In this example, a weatherproof receptacle should have been installed on the platform.
- Utilise connectors that are designed to stand up up to the abuse of the task. Connectors designed for light-duty use should not be used in an industrial environment.
Practice Non use flexible wiring in situations where frequent inspection would be difficult, where damage would be probable, or where long-term electrical supply is needed. Flexible cords cannot be used as a substitute for the fixed wiring of a structure. Flexible cords must not be . . .
- run through holes in walls, ceilings, or floors;
- run through doorways, windows, or similar openings (unless
physically protected);
- attached to edifice surfaces (except with a tension accept-upwardly
device within 6 feet of the supply stop);
- hidden in walls, ceilings, or floors; or
- hidden in conduit or other raceways.
The size of wire in an extension cord must be compatible with the amount of electric current the string will be expected to bear. The corporeality of electric current depends on the equipment plugged into the extension cord. Electric current ratings (how much electric current a device needs to operate) are oftentimes printed on the nameplate. If a power rating is given, it is necessary to dissever the ability rating in watts by the voltage to discover the current rating. For example, a ane,000-watt heater plugged into a 120-volt
circuit will demand near 10 amps of current. Let'southward look at another case: A 1-horsepower electrical motor uses electrical energy at the charge per unit of virtually 750 watts, so it will demand a minimum of virtually vii amps of current on a 120-volt circuit. But, electrical motors need additional current equally they startup or if they stall, requiring up to 200% of the nameplate electric current rating. Therefore, the motor would demand 14 amps.
Add to detect the full current needed to operate all the appliances supplied by the cord. Choose a wire size that can handle the total current.
| American Wire Gauge (AWG) | |
| Wire Size | Handles upwardly to |
| #10 AWG | thirty amps |
| #12 AWG | 25 amps |
| #xiv AWG | 18 amps |
| #16 AWG | xiii amps |
| Remember: The larger the gauge number, the smaller the wire! | |
The length of the extension cord also needs to exist considered when selecting the wire size. Voltage drops over the length of a string. If a cord is besides long, the voltage drop can be enough to damage equipment. Many electric motors simply operate safely in a narrow range of voltages and will not piece of work properly at voltages different than the voltage listed on the nameplate. Even though light bulbs operate (somewhat dimmer) at lowered voltages, do not assume electric motors volition work correctly at less-than-required voltages. As well, when electric motors showtime or operate under load, they crave more current. The larger the size of the wire, the longer a cord can be without causing a voltage drop that could damage tools and equipment.
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The grounding path for extension cords must be kept intact to continue you safe. A typical extension cord grounding organisation has iv components:
- a third wire in the cord, called a basis wire;
- a three-prong plug with a grounding prong on one end of the cord;
- a three-wire, grounding-type receptacle at the other terminate of the cord; and
- a properly grounded outlet.
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Electrical hazards exist when wires or other electrical parts are exposed. These hazards need to be controlled to create a safe piece of work environment. Isolation of energized electrical parts makes them inaccessible unless tools and special effort are used. Isolation can exist accomplished by placing the energized parts at least eight feet high and out of reach, or by guarding. Guarding is a type of isolation that uses various structures—like cabinets, boxes, screens, barriers, covers, and partitions—to close-off live electric parts.
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| This exposed electrical equipment is guarded by an 8-pes fence. |
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When the iron hit the supply wire, the laborer was electrocuted. A forklift operator heard the iron driblet to the basis at about 8:46 a.m. and plant the victim 5 minutes afterwards. He was pronounced dead on arrival at a local hospital.
- Co-ordinate to OSHA, the enclosure around the transformers was too short. The contend should have been at to the lowest degree 8 feet tall.
- The company in this case did not offer whatever formal safety training to its workers. All employers should develop prophylactic and health grooming programs and so their employees know how to recognize and avoid life-threatening hazards.
Take the following precautions to prevent injuries from contact with live parts:
- Immediately study exposed live parts to a supervisor or teacher. Every bit a student, y'all should never attempt to correct the condition yourself without supervision.
- Provide guards or barriers if live parts cannot be enclosed completely.
- Utilise covers, screens, or partitions for guarding that require tools to remove them.
- Replace covers that take been removed from panels, motors, or fuse boxes.
- Even when live parts are elevated to the required elevation (8 feet), care should be taken when using objects (like metal rods or pipes) that can contact these parts.
- Close unused conduit openings in boxes and then that foreign objects (pencils, metallic chips, conductive debris, etc.) cannot go inside and damage the circuit.
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| This cover cannot be removed without special tools. |
Insulation is made of material that does non acquit electricity (commonly plastic, condom, or fiber). Insulation covers wires and prevents conductors from coming in contact with each other or whatever other conductor. If conductors are allowed to make contact, a brusque circuit is created. In a short circuit, current passes through the shorting material without passing through a load in the circuit, and the wire becomes overheated. Insulation keeps wires and other conductors from touching, which prevents electrical brusk circuits. Insulation prevents live wires from touching people and animals, thus protecting them from electrical daze.
An test of the welding machine showed that there were exposed conductors in the auto's cables. At that place were numerous cuts and scrapes in the cables' insulation. On other parts of the machine, insulation was damaged or missing. Too, the auto did not have a ground connection.
Investigators concluded that the maintenance worker was electrocuted when he tried to turn off the welding machine, which was sitting on the cart. The metal frame of the machine had go energized due to the damaged insulation. When he touched the energized frame, he completed the conducting path to basis. The current traveled through his torso to ground. Since he was probably standing in water, the chance of a ground error was even greater.
You must take steps to decrease such hazards in your workplace:
- Footing circuits and equipment.
- Keep all equipment in skilful operating condition with a preventive maintenance program.
- Never use electric equipment or work on circuits in wet areas. If you find water or dampness, notify your supervisor immediately.
Insulation helps protect wires from concrete damage and conditions in the surroundings. Insulation is used on virtually all wires, except some ground wires and some high-voltage transmission lines.
Insulation is used internally in tools, switches, plugs, and other electric and electronic devices.
Special insulation is used on wires and cables that are used in harsh environments. Wires and cables that are cached in soil must have an outer roofing of insulation that is flame-retardant and resistant to wet, mucus, and corrosion.
In all situations, you must exist careful not to damage insulation while installing it. Do not allow staples or other supports to damage the insulation. Bends in a cable must have an inside radius of at to the lowest degree five times the diameter of the cable and so that insulation at a bend is not damaged. Extension cords come with insulation in a variety of types and colors. The insulation of extension cords is peculiarly important. Since extension cords oftentimes receive rough handling, the insulation tin be damaged. Extension cords might be used in wet places, so adequate insulation is necessary to prevent shocks. Because extension cords are frequently used near flammable materials (such as wood shavings and sawdust) a short in an extension cord could hands cause arcing and a fire.
Insulation on individual wires is ofttimes color-coded. In general, insulated wires used as equipment grounding conductors are either continuous light-green or green with yellowish stripes. The grounded conductors that complete a circuit are generally covered with continuous white or gray insulation. The ungrounded conductors, or "hot" wires, may be any color other than dark-green, white, or gray. They are usually black or red.
Conductors and cables must exist marked by the manufacturer to testify the post-obit:
- maximum voltage chapters,
- AWG size,
- insulation-type letter of the alphabet, and
- the manufacturer'southward name or trademark.
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| Arc-fault circuit breaker. |
Footing circuits and equipment
When an electrical organisation is not gro unded properly, a hazard exists. This is because the parts of an electrical wiring system that a person normally touches may be energized, or live, relative to ground. Parts like switch plates, wiring boxes, conduit, cabinets, and lights need to be at 0 volts relative to ground. If the arrangement is grounded improperly, these parts may be energized. The metallic housings of equipment plugged into an outlet need to be grounded through the plug.
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| Ground electric devices. |
Grounding is connecting an electrical system to the earth with a wire. Excess or stray current travels through this wire to a grounding device (commonly called a "basis") deep in the earth. Grounding prevents unwanted voltage on electric components. Metal plumbing is often used as a footing. When plumbing is used every bit a grounding conductor, it must also exist continued to a grounding device such as a conductive rod. (Rods used for grounding must be driven at to the lowest degree viii feet into the world.) Sometimes an electrical organisation volition receive a higher voltage than it is designed to handle. These high voltages may come from a lightning strike, line surge, or contact with a higher-voltage line. Sometimes a defect occurs in a device that allows exposed metal parts to become energized. Grounding will help protect the person working on a organization, the system itself, and others using tools or operating equipment continued to the organization. The extra current produced past the excess voltage travels relatively safely to the earth.
Grounding creates a path for currents produced past unintended voltages on exposed parts. These currents follow the grounding path, rather than passing through the torso of someone who touches the energized equipment. However, if a grounding rod takes a direct striking from a lightning strike and is buried in sandy soil, the rod should be examined to make sure it will still function properly. The heat from a lightning strike tin can cause the sand to turn into drinking glass, which is an insulator. A grounding rod must be in contact with clammy soil to be effective.
Leakage current occurs when an electrical current escapes from its intended path. Leakages are sometimes low-electric current faults that can occur in all electrical equipment because of clay, vesture, damage, or moisture. A good grounding system should be able to comport off this leakage electric current. A ground fault occurs when current passes through the housing of an electric device to ground. Proper grounding protects against ground faults. Ground faults are normally caused past misuse of a tool or damage to its insulation. This harm allows a blank conductor to touch metallic parts or the tool housing.
When you ground a tool or electrical system, you lot create a low-resistance path to the world (known every bit a ground connectedness). When done properly, this path has sufficient electric current-carrying capacity to eliminate voltages that may crusade a dangerous shock.
Grounding does not guarantee that you volition not be shocked, injured, or killed from lacking equipment. Even so, it greatly reduces the possibility.
Equipment needs to be grounded under any of these circumstances:
- The equipment is inside viii feet vertically and 5 feet horizontally of the floor or walking surface.
- The equipment is within eight feet vertically and 5 feet horizontally of grounded metal objects you could touch.
- The equipment is located in a wet or clammy expanse and is non isolated.
- The equipment is connected to a power supply past string and plug and is non double-insulated.
The use of GFCI'due south has lowered the number of electrocutions dramatically. A GFCI is a fast-acting switch that detects any difference in current between two circuit conductors. If either conductor comes in contact—either directly or through role of your body—with a ground (a situation known as a ground fault), the GFCI opens the circuit in a fraction of a second. If a current as small as 4 to six mA does non pass through both wires properly, only instead leaks to the ground, the GFCI is tripped. The current is close off.
There is a more sensitive kind of GFCI called an isolation GFCI. If a circuit has an isolation GFCI, the footing fault current passes through an electronic sensing circuit in the GFCI. The electronic sensing circuit has enough resistance to limit current to as little every bit 2 mA, which is also low to cause a dangerous shock.
GFCI'southward are commonly in the course of a duplex receptacle. They are besides available in portable and plug-in designs and as circuit breakers that protect an unabridged co-operative excursion. GFCI's tin can operate on both two- and three-wire ground systems. For a GFCI to piece of work properly, the neutral usher (white wire) must (one) exist continuous, (2) have low resistance, and (3) have sufficient current-carrying capacity.
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| Portable GFCI. |
GFCI's assist protect yous from electrical stupor by continuously monitoring the excursion. Yet, a GFCI does not protect a person from line-to-line hazards such as touching two "hot" wires (240 volts) atthe same fourth dimension or touching a "hot" and neutral wire at the same time. Also be aware that instantaneous currents can be high when a GFCI is tripped. A shock may even so be felt. Your reaction to the shock could cause injury, peradventure from falling.
Examination GFCI'south regularly by pressing the "test" button. If the circuit does not turn off, the GFCI is faulty and must be replaced.
An investigation showed that the mixing motor was in poor condition. The grounding pin had been removed from the male person end of the power string, resulting in a faulty ground. The circuit was equipped with a GFCI, merely information technology was not installed properly. A properly wired and functioning GFCI could accept sensed the ground fault in the motor and de-energized the circuit.
Take a look at what could have been washed to foreclose this death.
- The employer should have kept the motor in better condition. Power cords should be inspected regularly, and whatsoever missing prongs should be replaced.
- All pool-area electrical circuits should be installed by qualified electricians.
- The victim should accept worn insulating boots or shoes since she was handling electrical equipment.
- The employer should have followed the law. The NEC requires that all puddle-associated motors have a permanent grounding system. In this case, this regulation was not followed. Too, electric equipment is not permitted in areas without proper drainage.
- OSHA requires employers to provide a work environs gratuitous of safety and health hazards.
The NEC requires that GFCI'due south be used in these loftier-risk situations:
- Electricity is used most h2o.
- The user of electric equipment is grounded (by touching grounded material).
- Circuits are providing power to portable tools or outdoor receptacles.
- Temporary wiring or extension cords are used.
Specifically, GFCI's must be installed in bathrooms, garages, outdoor areas, crawl spaces, unfinished basements, kitchens, and near wet bars.
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| Install bonding jumpers around nonconductive material. |
| Use GFCI's to aid protect people in damp areas. |
| bonding—joining electric parts to assure a conductive path |
In order to assure a continuous, reliable electrical path to basis, a bonding jumper wire is used to brand sure electric parts are continued. Some physical connections, similar metal conduit coming into a box, might not make a good electrical connection considering of paint
or possible corrosion. To make a good electric connexion, a bonding
jumper needs to be installed.
A metal common cold water pipe that is office of a path to ground may need bonding jumpers around plastic antivibration devices, plastic water meters, or sections of plastic pipe. A bonding jumper is made of conductive material and is tightly connected to metal pipes with screws or clamps to bypass the plastic and assure a continuous grounding path. Bonding jumpers are necessary considering plastic does not bear electricity and would interrupt the path to footing.
Additionally, interior metal plumbing must be bonded to the ground for electrical service equipment in order to keep all grounds at the aforementioned potential (0 volts). Even metal air ducts should exist bonded to electric service equipment.
When a current exceeds the electric current rating of equipment or wiring, a hazard exists. The wiring in the circuit, equipment, or tool cannot handle the current without heating up or even melting. Not only will the wiring or tool be damaged, but the high temperature of the usher can also crusade a fire. To prevent this from happening, an overcurrent protection device (circuit breaker or fuse) is used in a circuit. These devices open a excursion automatically if they find current in excess of the electric current rating of equipment or wiring. This excess current tin be caused by an overload, short excursion, or high-level footing mistake.
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| Utilize overcurrent protection devices (circuit breakers or fuses) in circuits. |
Overcurrent protection devices are designed to protect equipment and structures from fire. They do not protect you from electrical daze! Overcurrent protection devices finish the catamenia of electric current in a excursion when the amperage is besides loftier for the circuit. A excursion breaker or fuse volition not stop the relatively pocket-size amount of current that can cause injury or death. Decease can result from 20 mA (.020 amps) through the breast (see Section 2). A typical residential excursion breaker or fuse will not shut off the excursion until a current of more than xx amps is reached!
Just overcurrent protection devices are not immune in areas where they could be exposed to physical damage or in hazardous environ-ments. Overcurrent protection devices can heat upwardly and occasionally arc or spark, which could cause a fire or an explosion in sure areas. Hazardous environments are places that contain flammable or explosive materials such as flammable gasses or vapors (Course I Hazardous Environments), finely pulverized flammable dusts (Class Ii Hazardous Environments), or fibers or metal filings that can grab burn down easily (Grade III Hazardous Environments). Chancy environments may be found in aircraft hangars, gas stations, storage
plants for flammable liquids, grain silos, and mills where cotton fibers may be suspended in the air. Special electrical systems are required in hazardous environments.
If an overcurrent protection device opens a circuit, there may be a problem forth the circuit. (In the case of circuit breakers, frequent tripping may besides indicate that the billow is defective.) When a circuit billow trips or a fuse blows, the crusade must be found.
A circuit breaker is one kind of overcurrent protection device. Information technology is a blazon of automatic switch located in a circuit. A circuit billow trips when too much current passes through information technology. A circuit breaker should not be used regularly to plough ability on or off in a circuit, unless the breaker is designed for this purpose and marked "SWD" (stands for "switching device").
A fuse is some other blazon of overcurrent protection device. A fuse contains a metal usher that has a relatively depression melting point. When as well much current passes through the metal in the fuse, information technology heats up within a fraction of a 2d and melts, opening the circuit. Later on an overload is found and corrected, a blown fuse must be replaced with a new one of appropriate amperage.
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Control contact with electrical voltages and control electrical currents to create a rubber work environs.
- Lock out and tag out circuits and machines.
- Forbid overloaded wiring by using the right size and type of wire.
- Prevent exposure to live electrical parts by isolating them.
- Prevent exposure to live wires and parts past using insulation.
- Prevent shocking currents from electric systems and tools by grounding them.
- Prevent shocking currents by using GFCI's.
- Prevent also much current in circuits by using overcurrent protection devices.
When Is Wire Size An Electrical Hazard?,
Source: https://www.elcosh.org/document/1624/893/d000543/section7.html
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