Electrical Safety

Aluminum Wiring

Between approximately 1965 and 1973, single-strand aluminum wiring was sometimes substituted for copper branch-circuit wiring in residential electrical systems due to the sudden escalating price of copper. After a decade of use by homeowners and electricians, inherent weaknesses were discovered in the metal that led to its disuse as a branch wiring material. Although properly maintained aluminum wiring is acceptable, aluminum will generally become defective faster than copper due to certain qualities inherent in the metal. Neglected connections in outlets, switches and light fixtures containing aluminum wiring become increasingly dangerous over time. Poor connections cause wiring to overheat, creating a potential fire hazard. In addition, the presence of single-strand aluminum wiring may void a homeowner’s insurance policy. Homeowners should talk with their insurance agents about whether the presence of aluminum wiring in their home is a problem that requires changes to their policy.
 

Facts and Figures

• In April 1974, two people were killed in a house fire in Hampton Bays, New York. Fire officials determined that the fire was caused by a faulty aluminum wire connection at an outlet.
• According to the Consumer Product Safety Commission (CPSC), "Homes wired with aluminum wire manufactured before 1972 ['old technology' aluminum wire] are 55 times more likely to have one or more connections reach fire hazard conditions than is a home wired with copper."

Aluminum as a Metal 

Aluminum possesses certain qualities that, compared with copper, make it an undesirable material as an electrical conductor. These qualities all lead to loose connections, when fire hazards become likely.
These qualities are as follows:
 

• higher electrical resistance. Aluminum has a high resistance to electrical current flow, which means that, given the same amperage, aluminum conductors must be of a larger diameter than that required by copper conductors.
• less ductile. Aluminum will fatigue and break down more readily when subjected to bending and other forms of abuse than copper, which is more ductile. Fatigue will cause the wire to break down internally and will increasingly resist electrical current, leading to a buildup of excessive heat.
• galvanic corrosion. In the presence of moisture, aluminum will undergo galvanic corrosion when it comes into contact with certain dissimilar metals.
• oxidation. Exposure to oxygen in the air causes deterioration to the outer surface of the wire. This process is called oxidation. Aluminum wire is more easily oxidized than copper wire, and the compound formed by this process – aluminum oxide – is less conductive than copper oxide. As time passes, oxidation can deteriorate connections and present a fire hazard.
• greater malleability. Aluminum is soft and malleable, meaning it is highly sensitive to compression. After a screw has been over-tightened on aluminum wiring, for instance, the wire will continue to deform or “flow” even after the tightening has ceased. This deformation will create a loose connection and increase electrical resistance in that location.
• greater thermal expansion and contraction. Even more than copper, aluminum expands and contracts with changes in temperature. Over time, this process will cause connections between the wire and the device to degrade. For this reason, aluminum wires should never be inserted into the “stab,” “bayonet” or “push-in” type terminations found on the back of many light switches and outlets.
• excessive vibration. Electrical current vibrates as it passes through wiring. This vibration is moreextreme in aluminum than it is in copper, and, as time passes, it can cause connections to loosen.

Identifying Aluminum Wiring

• Aluminum wires are the color of aluminum and are easily discernible from copper and other metals.
• Since the early 1970s, wiring-device binding terminals for use with aluminum wire have been marked CO/ALR, which stands for “copper/aluminum revised." 
• Look for the word "aluminum" or the initials "AL" on the plastic wire jacket. Where wiring is visible, such as in the attic or electrical panel, homeowners can look for printed or embossed letters on the plastic wire jacket. Aluminum wire may have the word "aluminum," or a specific brand name, such as "Kaiser Aluminum," marked on the wire jacket. Where labels are hard to read, a light can be shined along the length of the wire.
• When was the house built? Homes built or expanded between 1965 and 1973 are more likely to have aluminum wiring than houses built before or after those years.

Options for Correction

Aluminum wiring should be evaluated by a qualified electrician who is experienced in evaluating and correcting aluminum wiring problems. Not all licensed electricians are properly trained to deal with defective aluminum wiring. The CPSC recommends the following two methods for correction for aluminum wiring:
 

• Rewire the home with copper wire. While this is the most effective method, rewiring is expensive and impractical, in most cases.
• Use copalum crimps. The crimp connector repair consists of attaching a piece of copper wire to the existing aluminum wire branch circuit with a specially designed metal sleeve and powered crimping tool. This special connector can be properly installed only with the matching AMP tool. An insulating sleeve is placed around the crimp connector to complete the repair. Although effective, they are expensive (typically around $50 per outlet, switch or light fixture).

 
Although not recommended by the CPSC as methods of permanent repair for defective aluminum wiring, the following methods may be considered:

• application of anti-oxidant paste. This method can be used for wires that are multi-stranded or wires that are too large to be effectively crimped.
• pigtailing. This method involves attaching a short piece of copper wire to the aluminum wire with a twist-on connector. the copper wire is connected to the switch, wall outlet or other termination device. This method is only effective if the connections between the aluminum wires and the copper pigtails are extremely reliable. Pigtailing with some types of connectors, even though Underwriters Laboratories might presently list them for the application, can lead to increasing the hazard. Also, beware that pigtailing will increase the number of connections, all of which must be maintained. Aluminum Wiring Repair (AWR), Inc., of Aurora, Colorado, advises that pigtailing can be useful as a temporary repair or in isolated applications, such as the installation of a ceiling fan.
• CO/ALR connections. According to the CPSC, these devices cannot be used for all parts of the wiring system, such as ceiling-mounted light fixtures or permanently wired appliances and, as such, CO/ALR connections cannot constitute a complete repair. Also, according to AWR, these connections often loosen over time.
• alumiconn. Although AWR believes this method may be an effective temporary fix, they are warythat it has little history, and that they are larger than copper crimps and are often incorrectly applied.
• Replace certain failure-prone types of devices and connections with others that are more compatible with aluminum wire.
• Remove the ignitable materials from the vicinity of the connections.

 
 In summary, aluminum wiring can be a fire hazard due to inherent qualities of the metal.

Knob-and-Tube Wiring 

Knob-and-tube (K&T) wiring was an early standardized method of electrical wiring in buildings, in common use in North America from about 1880 to the 1940s. The system is considered obsolete and can be a safety hazard, although some of the fear associated with it is undeserved.


 

Facts About Knob-and-Tube Wiring:

•  It is not inherently dangerous. The dangers from this system arise from its age, improper modifications, and situations where building insulation envelops the wires.
• It has no ground wire and thus cannot service any three-pronged appliances.
• While it is considered obsolete, there is no code that requires its complete removal.
• It is treated differently in different jurisdictions. In some areas, it must be removed at all accessible locations, while others merely require that it not be installed in new construction. 
• It is not permitted in any new construction.

How Knob-and-Tube Wiring Works

 K&T wiring consists of insulated copper conductors passing through lumber framing drill holes via protective porcelain insulating tubes. They are supported along their length by nailed-down porcelain knobs. Where wires enter a wiring device, such as a lamp or switch, or were pulled into a wall, they are protected by flexible cloth or rubber insulation called loom.
 

Advantages of Knob-and-Tube Wiring:

•  K&T wiring has a higher ampacity than wiring systems of the same gauge. The reason for this is that the hot and neutral wires are separated from one another, usually by 4 to 6 inches, which allows the wires to readily dissipate heat into free air.
• K&T wires are less likely than Romex® cables to be punctured by nails because K&T wires are held away from the framing.
• The porcelain components have an almost unlimited lifespan.
• The original installation of knob-and-tube wiring is often superior to that of modern Romex® wiring. K&T wiring installation requires more skill to install than Romex® and, for this reason, unskilled people rarely ever installed it.

 

Problems Associated with K&T Wiring:

• Unsafe modifications are far more common with K&T wiring than they are with Romex® and other modern wiring systems. Part of the reason for this is that K&T is so old that more opportunity has existed for improper modifications.
• The insulation that envelopes the wiring is a fire hazard. It tends to stretch and sag over time.
• It lacks a grounding conductor. Grounding conductors reduce the chance of electrical fire and damage to sensitive equipment.
• In older systems, the wiring is insulated with varnish and fiber materials that are susceptible to deterioration.

Compared with modern wiring insulation, K&T wiring is less resistant to damage. K&T wiring insulated with cambric and asbestos is not rated for moisture exposure. Older systems contain insulation with additives that may oxidize copper wire. Bending the wires may cause insulation to crack and peel away.
 
K&T wiring is often spliced with modern wiring incorrectly by amateurs. This is perhaps due to the ease by which K&T wiring is accessed.

Building Insulation

K&T wiring is designed to dissipate heat into free air, and insulation will disturb this process. Insulation around K&T wires will cause heat to build up, and this creates a fire hazard. The 2008 National Electrical Code (NEC) requires that this wiring system not be covered by insulation. Specifically, it states that this wiring system should not be in…
 
hollow spaces of walls, ceilings and attics where such spaces are insulated by loose, rolled or foamed-in-place insulating material that envelops the conductors.
 
Local jurisdictions may or may not adopt the NEC’s requirement. The California Electrical Code, for instance, allows insulation to be in contact with knob-and-tube wiring, provided that certain conditions are met, such as, but not limited to, the following:

•  A licensed electrical contractor must certify that the system is safe. The certification must be filed with the local building department.
• Accessible areas where insulation covers the wiring must be posted with a warning sign. In some areas, this sign must be in English and Spanish.
• The insulation must be non-combustible and non-conductive. Normal requirements for insulation must be met. 

Modifications

When K&T wiring was first introduced, common household electrical appliances were limited to little more than toasters, tea kettles, coffee percolators and clothes irons. The electrical requirements of mid- to late-20^th century homes could not have been foreseen during the late 18^th century, a time during which electricity was seen as a passing fad to many people. Existing K&T systems are notorious for modifications made in an attempt to match the increasing amperage loads required by televisions, refrigerators, and a plethora of other electrical appliances. Many of these attempts were made by insufficiently trained handymen, rather than experienced electricians, whose work made the wiring system vulnerable to overloading.
 
Many homeowners adapted to the inadequate amperage of K&T wiring by installing fuses with resistances that were too high for the wiring. The result of this modification is that the fuses would not blow as often and the wiring would suffer heat damage due to excessive amperage loads. It is not uncommon for homeowners to find connections wrapped with masking tape or Scotch tape instead of electrical tape.
 

K&T Wiring and Insurance

Many insurance companies refuse to insure houses that have knob-and-tube wiring due to the risk of fire. Exceptions are sometimes made for houses with such systems that have been deemed safe by an electrical contractor.

Advice for Homeowners with K&T Wiring:

•  Have the system evaluated by a qualified electrician. Only an expert can confirm that the system was installed and modified correctly.
• Do not run an excessive amount of appliances in the home, as doing so can cause a fire. Where the wiring is brittle or cracked, it should be replaced. Proper maintenance is crucial. K&T wiring should not be used in kitchens, bathrooms, laundry rooms, or at the exterior. The wiring must be grounded in order to be used safely in these locations.
• Rewiring a house can take weeks and cost thousands of dollars, but unsafe wiring can cause fires, complicate real estate transactions, and make insurers skittish.
• Homeowners should carefully consider their options before deciding whether to rewire their house.
• The homeowner or an electrician should carefully remove any insulation that is found surrounding K&T wires.
• Prospective home buyers should get an estimate of the cost of replacing K&T wiring. They can use this amount to negotiate a lower price for the house.

 In summary, knob-and-tube wiring is likely to be a safety hazard due to improper modifications and the addition of building insulation.
 

Ungrounded Electrical Receptacles

 
Grounding of electrical receptacles (which some laypeople refer to as outlets) is an important safety feature that has been required in new construction since 1962, as it minimizes the risk of electric shock and protects electrical equipment from damage. Modern grounded 120-volt receptacles in the United States have a small, round ground slot centered below two vertical hot and neutral slots, and it provides an alternate path for electricity that may stray from an appliance. Older homes often have ungrounded, two- slot receptacles that are outdated and potentially dangerous.

 
Homeowners sometimes attempt to perform the following dangerous modifications to ungrounded receptacles:

While homeowners may be made aware of the limitations of ungrounded electrical receptacles, upgrades are not necessarily required. Many small electrical appliances, such as alarm clocks and coffee makers, are two-pronged and are thus unaffected by a lack of grounding in the home’s electrical system.
 
However, upgrading the system will bring it closer to modern safety standards, and this may be accomplished in the following ways:

Neither homeowners nor unqualified professionals should attempt to modify a building’s electrical components. Misguided attempts to ground receptacles to a metallic water line or ground rod may be dangerous.
 
In summary, adjustments should be made by qualified electricians -- not homeowners -- to an electrical system to upgrade ungrounded receptacles to meet modern safety standards and the requirements of today's typical household appliances and electronics.

Ground-Fault Circuit Interrupters (GFCIs) What is a GFCI?

A ground-fault circuit interrupter, or GFCI, is a device used in electrical wiring to disconnect a circuit when unbalanced current is detected between an energized conductor and a neutral return conductor. Such an imbalance is sometimes caused by current "leaking" through a person who is simultaneously in contact with a ground and an energized part of the circuit, which could result in a lethal shock. GFCIs are designed to provide protection in such a situation, unlike standard circuit breakers, which guard against overloads, short
circuits and ground faults.
 
It is estimated that about 300 deaths by electrocution occur every year, so the use
of GFCIs has been adopted in new construction, and recommended as an upgrade in older construction, in order to mitigate the possibility of injury or fatality from electric shock.
 

History

 
The first high-sensitivity system for detecting current leaking to ground was developed by Henri Rubin in 1955 for use in South African mines. This cold-cathode system had a tripping
sensitivity of 250 mA (milliamperes), and was soon followed by an upgraded design that allowed for adjustable trip-sensitivity from 12.5 to 17.5 mA. The extremely rapid tripping after earth leakage- detection caused the circuit to de-energize before electric shock could drive a person's heart into ventricular fibrillation, which is usually the specific cause of death attributed to electric shock.
 
Charles Dalziel first developed a transistorized version of the ground-fault circuit interrupter in 1961. Through the 1970s, most GFCIs were of the circuit-breaker type. This version of the GFCI was prone to frequent false trips due to poor alternating-current characteristics of 120-volt insulations.
Especially in circuits with long cable runs, current leaking along the conductors’ insulation could be high enough that breakers tended to trip at the slightest imbalance.
 
Since the early 1980s, ground-fault circuit interrupters have been built into outlet receptacles, and advances in design in both receptacle and breaker types have improved reliability while reducing instances of "false trips," also known as nuisance-tripping.
 

NEC Requirements for GFCIs

 
The National Electrical Code (NEC) has included recommendations and requirements for GFCIs in some form since 1968, when it first allowed for GFCIs as a method of protection for underwater swimming pool lights. Throughout the 1970s, GFCI installation requirements were gradually added for 120-volt receptacles in areas prone to possible water contact, including bathrooms, garages, and receptacles located outdoors.

The 1980s saw additional requirements implemented. During this period, kitchens and basements were added as areas that were required to have GFCIs, as well as boat houses, commercial garages, and indoor pools and spas. New requirements during the '90s included crawlspaces, wet bars and
rooftops. In 1996, GFCIs were mandated for all temporary wiring for construction, remodeling, maintenance, repair, demolition, and similar activities.
 
The 2008 NEC contains additional updates relevant to GFCI use, as well as some exceptions for certain areas. The 2008 language is presented here for reference.
 

2008 NEC on GFCIs

100.1 Definition

100.1 Definitions. Ground-Fault Circuit Interrupter. A device intended for the protection of personnel that functions to de-energize a circuit or portion thereof within an established period of time when a current to ground exceeds the values established for a Class A device.
 
FPN: Class A ground-fault circuit interrupters trip when the current to ground has a value in the range of 4 mA to 6 mA. For further information, see UL 943, standard for Ground-Fault Circuit Interrupters.
 

210.8(A)&(B) Protection for Personnel

210.8 Ground-Fault Circuit Interrupter Protection for Personnel.
 

1. Dwelling Units. All 125-volt, single-phase, 15- and 20-ampere receptacles installed in the locations specified in (1) through (8) shall have ground-fault circuit-interrupter protection for personnel.

 

1. bathrooms;
2. garages, and also accessory buildings that have a floor located at or below grade level not intended as habitable rooms and limited to storage areas, work areas, and areas of similar use;

 
Exception No. 1: Receptacles not readily accessible.
 
Exception No. 2: A single receptacle or a duplex receptacle for two appliances that, in normal use, is not easily moved from one place to another and that is cord-and-plug connected in accordance with 400.7(A)(6), (A)(7), or (A)(8).
 
Receptacles installed under the exceptions to 210.8(A)(2) shall not be considered as meeting the requirements of 210.52(G)

3. outdoors;

 
Exception: Receptacles that are not readily accessible and are supplied by a dedicated branch circuit for electric snow melting or de-icing equipment shall be permitted to be installed in accordance with the applicable provisions of Article 426.

4. crawlspaces at or below grade level.

 
Exception No. 1: Receptacles that are not readily accessible.
 
Exception No. 2: A single receptacle or a duplex receptacle for two appliances that, in normal use, is not easily moved from one place to another and that is cord-and-plug connected in accordance with 400.7(A)(6), (A)(7), or (A)(8).
 
Exception No. 3: A receptacle supplying only a permanently installed fire alarm or burglar alarm system shall not be required to have ground-fault circuit interrupter protection.
 
Receptacles installed under the exceptions to 210.8(A)(2) shall not be considered as meeting the requirements of 210.52(G)
 

6. kitchens, where the receptacles are installed to serve the countertop surfaces;
7. wet bar sinks, where the receptacles are installed to serve the countertop surfaces and are located within 6 feet of the outside edge of the wet bar sink;
8. boathouses;

 

2. Other Than Dwelling Units. All 125-volt, single-phase, 15- and 20-ampere receptacles Installed in the locations specified in (1), (2), and (3) shall have ground-fault circuit interrupter protection for personnel:

 

1. bathrooms;
2. rooftops;

 Exception: Receptacles that are not readily accessible and are supplied by a dedicated branch circuit for electric snow-melting or de-icing equipment shall be permitted to be installed in accordance with the applicable provisions of Article 426.

3. kitchens.

 

Testing Receptacle-Type GFCIs

 
Receptacle-type GFCIs are currently designed to allow for safe and easy testing that can be performed without any professional or technical knowledge of electricity. GFCIs should be tested right after installation to make sure they are working properly and protecting the circuit. They should also be tested once a month to make sure they are working properly and are providing protection from fatal shock.
 
To test the receptacle GFCI, first plug a nightlight or lamp into the outlet. The light should be on. Then press the "TEST" button on the GFCI. The "RESET" button should pop out, and the light should turn off.

If the "RESET" button pops out but the light does not turn off, the GFCI has been improperly wired. Contact an electrician to correct the wiring errors.
 
If the "RESET" button does not pop out, the GFCI is defective and should be replaced.
 
If the GFCI is functioning properly and the lamp turns off, press the "RESET" button to restore power to the outlet.
 

Arc-Fault Circuit Interrupters (AFCIs)

Arc-fault circuit interrupters (AFCIs) are special types of electrical receptacles or outlets and circuit breakers designed to detect and respond to potentially dangerous electrical arcs in home branch wiring.
 

How do they work?

 
AFCIs function by monitoring the electrical waveform and promptly opening (interrupting) the circuit they serve if they detect changes in the wave pattern that are characteristic of a dangerous arc. They also must
be capable of distinguishing safe, normal arcs (such as those created when a switch is turned on or a plug is pulled from a receptacle) from arcs that can cause fires. An AFCI can detect, recognize and respond to very small changes in wave pattern.
 

What is an arc?

 When an electric current crosses an air gap from an energized component to a grounded component, it produces a glowing plasma discharge known as an arc. For example, a bolt of lightning is a very large, powerful arc that crosses an atmospheric gap from an electrically charged cloud to the ground or another cloud. Just as lightning can cause fires, arcs produced by domestic wiring are capable of producing high levels of heat that can ignite their surroundings and lead to structure fires.
 
According to statistics from the National Fire Protection Agency for the year 2005, electrical fires damaged approximately 20,900 homes, killed 500 people, and cost $862 million in property damage.

Although short-circuits and overloads account for many of these fires, arcs are responsible for the majority and are undetectable by traditional (non-AFCI) circuit breakers.
 

Where are arcs likely to form?

Arcs can form where wires are improperly installed or when insulation becomes damaged. In older homes, wire insulation tends to crystallize as it ages, becoming brittle and prone to cracking and chipping. Damaged insulation exposes the current-carrying wire to its surroundings, increasing the chances that an arc may occur.
 
Situations in which arcs may be created:

•  electrical cords damaged by vacuum cleaners or trapped beneath furniture or doors.
• damage to wire insulation from nails or screws driven through walls.
• appliance cords damaged by heat, natural aging, kinking, impact, or over-extension.
• spillage of liquid.
• loose connections in outlets, switches and light fixtures.

Where are AFCIs required?

Locations in which AFCIs are required depend on the building codes adopted by their jurisdiction.
 
The 2006 International Residential Code (IRC) requires that AFCIs be installed within bedrooms in the following manner:
 
E3802.12 Arc-Fault Protection of Bedroom Outlets. All branch circuits that supply120-volt, single-phase, 15- and 20-amp outlets installed in bedrooms shall be protected by a combination-type or branch/feeder-type arc-fault circuit interrupter installed to provide protection of the entire branch circuit.
 
Exception: The location of the arc-fault circuit interrupter shall be permitted to be at other than the origination of the branch circuit, provided that:
 
 the arc-fault circuit interrupter is installed within 6 feet of the branch circuit overcurrent device, as measured along the branch circuit conductor; and
 the circuit conductors between the branch circuit overcurrent device and the arc-fault circuit interrupter are installed in a metal raceway or a cable with metallic sheathing.
 
The National Electrical Code (NEC) offers the following guidelines concerning AFCI placement within bedrooms:

Dwelling Units. All 120-volt, single-phase, 15- and 20-ampere branch circuits supplying outlets installed in dwelling units in family rooms, dining rooms, living rooms, parlors, libraries, dens, sun rooms, recreation rooms, closets, hallways, and similar rooms or areas shall be protected by a listed arc-fault circuit interrupter, combination-type installed to provide protection of the branch circuit.
 
Some jurisdictions do not yet require their implementation in locations where they can be helpful.

What types of AFCIs are available?

 AFCIs are available as circuit breakers for installation in the electrical distribution panel.
 

Nuisance Tripping

An AFCI may activate in
situations that are not dangerous and create needless power shortages. This can be particularly annoying when an AFCI stalls power to a freezer or refrigerator, allowing its contents to spoil. There are a few procedures an electrical contractor can perform in order to reduce potential “nuisance tripping," such as:
 

• Check that the load power wire, panel neutral wire, and load neutral wire are properly connected.
• Check wiring to ensure that there are no shared neutral connections.
• Check the junction box and fixture connections to ensure that the neutral conductor contacts a grounded conductor.

Arc Faults vs. Ground Faults 

It is important to distinguish AFCI devices from ground-fault circuit interrupter (GFCI) devices. GFCIs detect ground faults, which occur when current leaks from a hot (ungrounded) conductor to a grounded object as a result of a short circuit. This situation can be hazardous when a person unintentionally
becomes the current’s path to the ground. GFCIs function by constantly monitoring the current flow between hot and neutral (grounding) conductors, and activate when they sense a difference of 5 milliamps or more. Thus, GFCIs are intended to prevent personal injury due to electric shock, while AFCIs prevent personal injury and property damage due to structure fires.
 
In summary, AFCIs are designed to detect small arcs of electricity before they have a chance to lead to a structure fire.

Electric Fences

 Electric fences are a "fear" barrier that use electric shock to delineate a boundary and discourage animals and people from crossing it. Primarily, they are used to protect livestock and domestic pets by preventing them from leaving a sanctioned area and by deterring predators from entering the area.
 
An effective electric fence involves the interconnection of the following four components:

•  The energizer turns low-voltage battery power, household current, or converted sunlight into a high-voltage electric shock.
• The conductor is the wire that transmits the energizer’s shock to the animal or person who touches it. This is usually galvanized or aluminum-coated steel wire, or poly-tape or poly-rope wire. Manufactured in a number of configurations, all “poly” wires contain tiny stainless steel or copper wires woven into the synthetic fabric, enabling them to conduct electricity.
• The post supports the conductor at the desired height, while the insulator prevents the electricity in the wire from leaking into the ground through the post. Some posts are non- conductive and thus do not require an insulator.
•  The ground is typically composed of metal rods driven into the soil near the energizer and are connected to it by a wire. A complete circuit occurs when an animal or person touches the conductor, allowing electricity to flow from the conductor through their body and into the soil, where moisture carries the current to the ground rods and back into the energizer. The absence of a ground circuit is how a bird can casually rest on a high-voltage power line.

 
In general, an electric fence should be supplied with only enough power to startle -- not injure -- so that an animal that brushes up against the fence will recoil but not suffer electrical burns or permanent injury. The feeling should be similar to the stinging sensation of a snapped rubber band. Exceptions are made for prisons, military installations, and vital utility stations to discourage escapes and vandalism attempts.
 
Fences that are too strongly electrified for their application, whether by accident or design, are a serious safety hazard. Aside from unnecessarily and inhumanely exposing farm animals or pets to unsafe shocks, homeowners must consider the inherent dangers that these fences may pose to firefighters, police and
trespassers. Note that “trespasser” can refer to an innocent child, such as a 6-year-old Texas girl who was killed instantly when she touched a neighbor’s electric fence. The investigating police captain said the amperage was far too high, “enough to power half of a house. She didn’t have time to scream for help, close her eyes... nothing,” according to KLTV. The owner of the fence pleaded guilty to criminally negligent homicide.
 
Other cases of over-powered fences abound; an elderly New York woman was killed when she tried to free her pet from an electric fence. The voltage was too high and the fence lacked a regulator to pulse the shock. A Colorado man even succumbed to his own fence –- a DIY project designed to keep his dogs in the yard, yet set to deliver lethal voltage, and designed without a regulator. (He did, however, receive a posthumous Darwin Award for his efforts.)
 

A few Additional Tips:

•  Lightning is one of the main causes of electric fence fires and controller malfunction. Use the following strategies to minimize lightning dangers:

• Disconnect the controller from the fence line and power source before a storm is expected.
• Install a lightning diverter (commonly referred to as a lightning arrestor) between the fence and the controller. This will divert a lightning strike’s electricity to the earth before it does any damage to the controller.
• Install a surge suppressor to protect the controller on the utility side. The suppressor is plugged into the outlet and the controller is plugged into the suppressor.
• Install a cutoff switch as a quick way to disconnect the fence from the controller without actually getting near the fence. This switch also allows the fence to be conveniently turned off while it’s being worked on.

 

• The energizer must be sized properly for the type of animal to be contained within the perimeter. Extra voltage may be required for sheep, for instance, as their thick wool (especially in the winter) is an effective insulator against shock. Their burned wool can wrap around the conductor and further nullify the shock against the rest of the herd, as the other sheep follow the first sheep into the road, a neighbor’s yard, or into a waiting pack of hungry coyotes. Of course, the size of the animal is also a factor, as a small dog will not need as much of a jolt as a horse. The length of the fence must be considered, too, as the potency of the shock will dissipate if it's forced to travel too far from the conductor.
•  Poor grounding weakens the electric shock and can interfere with radios, telephones and televisions. Multiple ground rods should be installed, each 6 to 8 feet long, and attached with adequate ground clamps. In very dry or cold climates, a ground wire may be needed to run parallel to the hot wire so that the system does not depend on insulating dry or frozen soil.
• Poly-tape and poly-rope give greater tensile strength and are useful in high-voltage applications, although most electric fences are made from aluminum or galvanized steel. Never use more than one type of metal, as galvanic corrosion can occur when two different metals are hooked together, weakening the connection and the whole electric fence.
• Fences should be equipped with warning signs that alert passersby to their danger, as it isn’t always obvious that a fence is electrified. In one bizarre instance that was conveniently captured by a security camera, a man was knocked unconscious when he urinated on a fence that he did not realize was electrified. Signage will also protect the homeowner against liability.
• Equip the fence with a light that shines when the fence is not operational. This way, fence operators can quickly fix a malfunction before penned animals become wise to the failing. Professionals can tell if a fence is working by touching the metal end of a long screwdriver to the conductor while holding the plastic insulated end. An active fence should create a visible, audible arc. Do not use an uninsulated item for this purpose, such as a blade of grass.
• Never touch a fence that may be electrified (or any live circuits of hazardous voltage) with two hands, as this will allow the current to travel through the heart and lungs. Always keep one hand in your pocket so you don’t accidentally touch something that will turn a painful but non-lethal shock into cardiac arrest.
• Never electrify barbed-wire fences. It takes little imagination to picture what will happen if electrified barbs become trapped in an animal’s fur.
• Keep flammable materials far from the electric fence. Small sparks and arcs can easily occur due to weather conditions, lightning strikes, vegetation brushing against the fence, and fence malfunctions.
• Be sure to purchase high-quality, long-lasting insulators that will not degrade from exposure to ultraviolet light. Cheap insulators will grow weak and eventually shatter.
• Plant fence posts solidly, at least 2 feet in the ground in solid earth or concrete, especially if you plan to contain large animals. Space the posts far enough apart so that the wires have room to bend, rather than forcing undue stress on the posts and insulators.

In summary, electric fences are useful and practical deterrents in a number of applications, both commercial and residential. But improperly maintained or designed electric fences can seriously injure or kill animals and humans.
 

Generators

Homeowners may use a generator to supply electricity to their home in the case of a power outage, either out of necessity or convenience. Homeowners may want to know about generators and the potential hazards they present when improperly wired or utilized.
 

Generator Types

There are two main types of generators: permanently installed standby generators; and gasoline- powered portable generators.
 

Standby Generators

 Standby generators typically operate on natural gas or liquid propane. They remain fixed in place outside the home and are designed to supply on-site power to specified circuits through a home's electrical wiring. These generators work in tandem with a manual or automatic transfer switch, which automatically detects an interruption in grid-
powered electricity and subsequently transfers over electrical input to the generator. The transfer switch suspends input from the generator once it senses that utility-powered electricity has resumed. Generators for small- to medium-size homes are typically air-cooled and employ fans to regulate the temperature inside the unit. Liquid-cooled units are used for the larger energy loads in larger homes.
 
Some advantages of standby generators are as follows:

• They may be turned on manually, or they may be programmed to switch on automatically in the case of a power outage even when no one is home.
• Power may be supplied for extended periods of time.
• Hard-wired systems, such as a home's furnace, well pump and air conditioner, may maintain continuous power.
• Uninterrupted power can be supplied to systems that must remain turned on continuously, such as home medical equipment used for breathing, etc

Disadvantages of standby generators:

• Installation may require a permit.
• A qualified technician, such as an electrician, is required to install the ATS and to determine the electrical load requirements for the circuits in the home.
• Routine maintenance is required.
• Standby generators may be prohibitively expensive for the average homeowner.

Portable Generators

Gasoline-powered portable generators are typically smaller in size and power capacity than permanently installed generators. They are designed so that corded electrical devices can be plugged directly into them.
 
Advantages of portable generators:

• They’re versatile. They may be used at home or transported and utilized in remote locations, such as a campground or construction site. They do not require complicated installation.
• They typically do not require a permit. Portable units are generally less expensive than standby generators.

 
Disadvantages of portable generators:

•  Devices that are hard-wired into a home's electrical system cannot be powered by a portable generator if no transfer switch is installed.

Hazards

• Portable and standby generators produce dangerous carbon monoxide (CO) gas, which can be deadly if inhaled.
• Inexperienced installers are exposed to the risk of electrical shock. Only qualified electricians should attempt to install a generator.
• Overloading a generator may result in reduced fuel efficiency, damage to appliances, or fire. Standby generators and their required transfer switches that are incorrectly wired or missing may result in "back-feed" -- a hazardous condition in which an electrical current is fed back into the grid -- which could potentially electrocute and kill homeowners, utility workers, and others who are using the same utility transformer.
• Connecting a portable generator directly into a home's wall outlet can also cause dangerous back-feed.
• Generators that are exposed to water or that are not properly grounded can cause electrocution.
• Gasoline for portable generators is highly flammable and may cause a fire when exposed to an open flame or when spilled on the hot generator.
• Over-taxed cords attached to a portable generator may cause a fire.