How can Arc Faults be prevented in older homes?

Home fires are a major problem in the United States

Older Homes Pose an Even Greater Threat

Many of these fires occur in aging homes. Today, our dependence on electricity is increasing, and we are expecting more out of our home's electrical system. According to the U.S. Census Bureau, half of the homes in use in the United States were built before 1973. These homes were built before many of the electronics and appliances we use today were even invented. Unfortunately, our increased demands for energy can overburden an older home's electrical system causing fires or electrocutions.

Put it into perspective:

  • 1/2 of the homes in the United States were built before the advent of the drip-type coffee maker or garage door opener.
  • 1/3 were built before the hair dryer or electric can opener were invented.
  • This does not even take into account the recent explosion in the use of computers, cell phones, and other personal electronic devices

Electrocutions can be Prevented

Fire is not the only danger. Each year, hundreds of people in the U.S. are electrocuted in their own homes.
Many electrocutions and home electrical fires can be prevented by using more up-to-date technology and by recognizing warning signs your home may be showing.

This lifesaving technology includes:

  • AFCI's – a new type of circuit breaker that recognizes potential fire hazards and immediately shuts off the power.
  • GFCI's – special outlets that have saved thousands of people from shocks and burns over the last three decades.
  • TRO's – new outlets designed to protect small children from inserting foreign objects into them.


Aging Happens but fires don't have to

Top Causes of Arc Faults

  • Loose or improper connections, such as electrical wires to outlets or switches
  • Frayed appliance or extension cords • Pinched or pierced wire insulation, such as a wire inside a wall nipped by a nail or a chair leg sitting on an extension cord
  • Cracked wire insulation stemming from age, heat, corrosion, or bending stress
  • Overheated wires or cords
  • Damaged electrical appliances
  • Electrical wire insulation chewed by rodents


What is an Arc Fault?

An arc fault occurs when electricity is unintentionally released from home wiring, cords, or appliances because of damage or improper installation. This release of electricity can cause surrounding material to catch fire. According to the National Fire Protection Association, electrical arcing is the source of ignition in more than 30,000 fires annually. These fires are responsible for the deaths and injuries of hundreds of people and cause more than $750 million in direct property damage.


A Consumer Product Safety Commission report revealed a number of factors that contribute to electrical fires in existing homes, including improper alterations, deterioration due to aging, and faulty products. These factors often cause arc faults, which are a leading cause of home fires.


How can Arc Faults be prevented in older homes?

Arc Fault Circuit Interrupters (AFCI's) are devices that replace standard circuit breakers in the electrical service panel. AFCI's detect arc faults and shut down power to a circuit in milliseconds. The U.S. Department of Housing and Urban Development's Healthy Homes report lists lack of AFCI's among the primary residential hazards associated with burns and fire-related injuries.

These devices are so effective that the 2008 Edition of the National Electrical Code® requires that almost EVERY circuit in new homes be protected by AFCI's


Installing & Testing AFCI's

AFCI circuit breakers should be installed by a licensed electrician. They should be tested regularly after installation to make sure they are working properly and protecting the circuit.


Why is it important to have an AFCI breaker installed in my home?

An AFCI provides a higher level of protection than a standard circuit breaker by detecting and removing the hazardous arcing condition before it becomes a fire hazard. Hidden electrical fires can spread quickly, delaying detection by smoke alarms.


Ground Fault Circuit Interrupters (GFCIs)

GFCI Quick Tips

A GFCI should be used in any area where water may come in contact with electrical products.

  • Put a ground fault circuit interrupter (GFCI) between your electric power source and your electric product.
  • Test your GFCI monthly and after every major electrical storm.
  • If you have a home without GFCIs, consult a qualified, licensed electrician about adding this important protection; purchase plug-in units or a portable GFCI to provide individual receptacle or load protection.


Over the last three decades, Ground Fault Circuit Interrupters (GFCIs) have saved thousands of lives and prevented many more injuries. Found mostly in areas where electrical products might come in contact with water
(i.e. bathrooms, kitchens, and outdoors), a GFCI is a special type of outlet designed to trip before a deadly electrical shock can occur. Just 25 years after the GFCI was introduced, the number of accidental electrocutions in the United States has been cut in half, even though electricity use has doubled. If GFCIs were installed in older homes, experts suggest that 70 percent of the approximately 400 electrocutions that occur each year in the home could be prevented.


How does the GFCI work?

GFCIs constantly monitor electricity flowing in a circuit. If the electricity flowing into the circuit differs by even a slight amount from that returning, the GFCI will
quickly shut off the current flowing through that circuit. The advantage of using GFCIs is that they can detect even small variations in the amount of leakage current; leakage too small to trip a fuse or circuit breaker.


Testing Your GFCI
GFCIs should be tested once a month to make sure they are working properly.

The nightlight should go out when the "Test" button is pushed. If the light does not go out, then the GFCI may have been improperly wired or damaged and does not offer shock protection. In this case, contact a licensed electrician to check the GFCI and correct the problem.


Older homes do not have technology that saves children

Every year, nearly 2,400 children are injured by inserting objects such as keys or hairpins into electrical outlets. This means that seven children per day are treated in emergency rooms for injuries due to contact with outlets. The vast majority of these incidents involve children under the age of six.

These injuries can be prevented

Using a plastic outlet cap is a common solution to prevent children from sticking objects into outlets, but unfortunately, plastic caps are not the safest option and can be easily removed by a young child. A safer solution is installing tamper-resistant outlets. These specialized outlets have been so effective in preventing injuries to children that the 2008 National Electrical Code requires that tamper resistant outlets be installed in all new homes constructed. However, these inexpensive products can easily be incorporated into existing homes as well.


What are Tamper-Resistant Outlets?

Tamper-Resistant Outlets are standard wall outlets that feature an internal shutter mechanism that protects children from sticking objects into the receptacle (like hairpins, keys and paper clips).
The spring-loaded shutter system in the outlet only allows electricity to flow when equal pressure is applied simultaneously to both shutters such as when an electrical plug is inserted. During unused conditions, both shutters are
closed, and openings are covered.


Are they easy to install in older homes?

Yes. It is easy to retrofit an older home with tamper-resistant receptacles. Installation of tamper-resistant receptacles is identical to installation of standard receptacles.

What do Tamper-Resistant Outlets cost?

You can replace common electrical outlets for tamper-resistant receptacles for as little as two dollars per outlet in existing homes. ESFI estimates that tamper-resistant receptacles will add less than $50 to the cost of a new home's electrical system.


The Electrical Safety Foundation International (ESFI) is dedicated exclusively to promoting electrical safety. ESFI is a 501(c)(3) organization funded by electrical manufacturers and distributors, independent testing laboratories, utilities, safety and consumer groups, and trade and labor associations. ESFI sponsors National Electrical Safety Month each May, and engages in public education campaigns and proactive media relations to help reduce property damage, personal injury and death due to electrical accidents.
Electrical safety tips are available on the Electrical Safety Foundation International's Web site,, or call (703) 841-3229.

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AFCI circuit breakers: valuable safeguard against electrical fires

By Michael Shields, PE, Senior Electrical Engineer, SEi Companies, Boston -- Consulting-Specifying Engineer, 11/1/2007

How many times have you seen or heard of a home destroyed by fire due to faulty wiring? Oftentimes, it is not recently installed wiring, but wiring that had been in the walls for years.

Building occupants would hope that because considerable time has elapsed since installation, they could rest easy knowing that the wiring is safe and free of fault.

Well, not necessarily. Wires still cause fires, even years after installation. The phenomenon most likely responsible for these faulty wiring fires is something called an arc fault. Arc faults may start as a result of a small defect or damage to a cable, and grow over time into something far more significant. To protect against arc faults, a type of circuit breaker called an arc fault circuit interrupter (AFCI) was developed in the 1990s. The first official requirement for AFCIs is in the 2002 National Electric Code (NEC) and applied to bedroom circuits only.

Now, the 2008 NEC, published in September, expands this requirement to include nearly all receptacle circuits in dwelling units. Anyone involved in residential construction can expect to hear more about these devices in the not-too-distant future.

To fully understand an arc fault, we must first understand the difference between an arc fault and a bolted fault. Figure 1 illustrates the difference between a regular, or bolted fault and an arc fault. We can follow this figure to discuss how AFCI circuit breakers work.

Figure 1 - When insulation is damaged to an extent that conducts either come in direct contact with one another or are connected by a metal object such as in Figure 1b, there is a bolted fault. The resistance in the conductors and through the nail is low.

I will explain why an arc fault may exist undetected and in fact be harmless for long periods of time before sparking disaster—literally. But first, look at 1a in Figure 1, which shows that conductors come with a color-coded plastic coating designed to keep them from touching one another. Note that the overall sheath encasing these conductors is not shown for simplicity's sake. When the insulation becomes damaged to an extent that conductors either come in direct contact with one another or are connected by a metal object such as in 1b in Figure 1—where the metal object is a nail—one gets what's known as a bolted fault. The resistance in the conductors and through the nail is low.

As a consequence, currents as high as 10,000 amps—sometimes more—can occur. This sounds serious, and it is. However, conventional circuit breakers effectively protect against this scenario. Upon sensing this high current, conventional circuits open in less than 1/10th of a second.

An arc fault is similar inasmuch as conductor insulation damage is involved. However, with an arc fault, the conductors are not in direct contact with one another, nor are they connected by a metal object.

Instead, because there are exposed conductors relatively close to each other, an arc forms between the two. The current in this case literally has to jump an air gap to get from one conductor to the next. Because air is a poor conductor, the resultant current is relatively small, often much too small to trip a conventional breaker.

In this case, the arc is outside the cable and continues indefinitely. When protected by a conventional breaker, the resultant heat may start a fire.

AFCI is yet another example of an advance in solid state technology. These breakers actually monitor the waveform pattern—or signature—rather than just the magnitude of the circuit that they are feeding. When AFCIs detect a pattern similar to the blue one in Figure 2, they recognize this signature as being an arc fault. As can be seen in the figure, an arc fault is characterized by a steady, relatively low-level, high-frequency current waveform.

However, one growing pain problem that this technology encountered when it first came into use involved normal, controlled, and acceptable arcing in electrical circuits. Examples of a normal arc include the arc that is seen when pulling out an electrical cord or the arc a light switch makes when it is operated. Power tools are another example, as power tools generate a sustained arc while being operated.

How does the AFCI breaker know when to trip and when not to? As it turns out, all of these types of electrical arcs have subtle differences in their signatures. As AFCI technology has evolved, it has reached a point where it can effectively filter out normal and safe arcing and only trip on the occurrence of a true arc fault.

Figure 2 - AFCIs monitor wave form. When they detect a pattern similar to the blue one, AFCIs recognize this signature as being an arc fault.

An arc fault can begin with the smallest of damage to conductor insulation. At first, an imperceptible current flows through that weak link from one conductor to another. Over time, further damage develops as the insulation is heated by the arc beyond its tolerance. Eventually, the damage becomes significant enough to allow a more intense arc and to ultimately cause a fire.

The intent of this article is not to scare anyone. The fact of the matter is electrical wiring, when installed correctly, results in relatively few fires—let alone fatalities. The fact remains that AFCI circuit breakers can make projects safer ones. They are about 8 times more expensive than a regular breaker ($60 vs. $7.50), but the labor to install them is the same. It strikes me as a small price to pay. Regardless, as it looks right now, if you're building residential construction in 2008 and beyond, you will not have a choice.

And occupants of the building where you design electrical systems can rest easy that new wiring will be free of arc fault.