Understanding the problem of Arc Faults and House Fires
According to the Consumer Products Safety Commission (CPSC), approximately 40,000 fires are caused annually by problems with home electrical wiring. For the last five years, electrical wiring systems have been one of the leading causes of fire deaths, claiming between 260 and 380 lives per year and costing more than $650 million annually.
In 1998, according to the latest statistics released by the CPSC, fire originating in the electrical distribution system accounted for more than 10 % of all home fires.
What is an Arc Fault?
Many times the culprit is an arc fault. An arc is a discharge of electric current across a gap. Many of us have seen an arc such as from an arc welder or sparks from a downed power line. An arc fault is an unintended arc flowing through an unintentional path.
Common causes for arc faults in a house are:
- Loose or improper connections, such as electrical wires to outlets or switches
- Frayed or ruptured appliance or extension cords.
- Pinched or pierced wire insulation, such as a wire inside a wall nipped by a nail or screw or a chair leg setting on an extension cord.
- Cracked wire insulation stemming from age, heat, corrosion or bending stress
- Overheated wire or cords.
- Damaged electrical appliances
- Wires or cords touching vibrating metal
- Electrical wire insulation chewed by rodents.
When an arc fault occurs inside the walls or ceiling, or inside an electrical appliance, temperatures can exceed 10,000 degrees Fahrenheit. Nearby combustibles like wood studs or insulation can be ignited by an electrical arc.
Fortunately, companies have developed arc fault circuit interrupters (AFCI) to help avoid fires caused by arc faults. They look and work just like conventional circuit breakers and fit into electrical panels in the same way. But they provide additional protection against arc faults.
Conventional circuit breakers “trip” if an overload or short circuit is detected, which shuts off the electrical power. They protect against overloads and short circuits with thermal and magnetic protection, respectively. AFCI’s, however, not only protect against overloads and short circuits, they can also electronically sense arcing and “trip.”
Dangers of Aluminum Wiring
Primarily in the 1960′s and 1970′s, many electrical contractors used aluminum wiring instead of cooper wiring as a way to save money and lower construction costs. However, a number of electrical fires have been attributed to aluminum wiring. Many building codes have been rewritten to not allow the use of aluminum wire for branch circuit wiring in houses.
Copper vs. Aluminum
- Tests have demonstrated aluminum wiring has inherent properties that make it more susceptible to fires when it was not installedcorrectly. Here are some of the problems with using aluminum wiring to conduct electricity.
- Aluminum does not conduct electricity as well as copper. An aluminum wire generates more heat.
- Aluminum is more brittle than copper. Wire is more likely to break or crimp if it is brittle. Arcing can occur if a wire breaks or crimps. This can cause very high temperatures inside the wall or ceiling.
- Aluminum is more likely to corrode than copper.
- Aluminum will oxidize if it comes in contact with moisture. This oxidation removed the pure aluminum and makes the wire thinner. A thinner wire creates more heat when electrical current is running through it.
- Oxidation also causes the wire to expand, puts pressure on the protective plastic coating on the wire, and can cause the plastic to split. If any of these occur, arcing can occur at these points.
- Aluminum expands and contacts more than copper. This puts additional stress at all connections such as outlets and switches. If these become loose, arcing can occur at these points.
If contemplating buying an older home with aluminum wiring or updating a home with aluminum wiring, contact a certified electrical to gain their expertise regarding the dangers of aluminum wiring.
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Federal Pacific Electric Panels – Fires Waiting to Happen
Federal Pacific Electric “Stab-Lok” service panels and breakers are dangerous and can fail, leading to electrical fires. The problem is that some 240-Volt FPE circuit breakers and possibly also some 120- Volt units simply may not work.
It has been suggested that there are as many as 28 million of these breakers in use in the U.S. Which means that in some conditions as many as one million of them may fail to provide proper fire protection.
But where are they? Most homeowners whose houses are served by these panels are unaware of the hazards. So too are some inspectors and contractors. Because most homeowners do not order periodic electrical safety inspections, the presence of these panels is often undiscovered until an inspection made in the course of renovating or selling a property. Our field experience indicated that even when problems occur with this equipment, often it is simply removed or replaced with little publicity. Neither manufactures nor some electricians are inclined to frighten consumers.
These breakers can fail to trip at an alarming rate- At a modest overload (135% of rating) switches that had never been touched (never mechanically switched) were energized on both poles. These failed 25% of the time, followed by a lockup that meant the switch would never trip in the future at any overload. Once these switches had been flipped on and off (mechanically energized), failures increased to 36%.
Worse, when individual poles on these switches were energized under the same conditions, 51% of the “virgin” switches failed, and for switches that had been mechanically energized, a whopping 65% of them failed!
When a circuit breaker will not trip in response to an overload there is a serious risk of fire.
Homeowners and renovators who encounter these panels should consider replacing them with new equipment. Panel replacement, can involves significant expenses depending on service size and other factors, however the costs far out way the costs associated with a total fire loss.
But identifying one of these defects can lead to an argument and in some cases, even lawsuits! For example, a knowledgeable inspector or contractor observes one of these panels and recommends a replacement. An owner or another inspector, unaware of the background, refuses to cooperate, and in insists there is “no problem”. Who’s right?
There is indeed “A problem.” FPE panels and circuit breakers are a “safety related defect.” In some conditions the equipment may not provide the safety protection (against fire) that was intended.
This defect is associates with FPE panels and circuit breakers manufactured in the 1970′s and possibly extending to current equipment. Testing was performed in 1982-2 by Wright Malta Corporation for the US Consumer Product Safety Commission.
What actually happens to cause unsafe conditions? Testing performed on FPE 2-pole (240v) circuit breakers indicated that in some overload conditions, particularly when one pole of th breaker is overloaded, the circuit breaker will not trip. Some tests showed that as many as 65% of the circuit breakers would malfunction.
Once this malfunction has occurred the breaker is “locked” and it will not trip under any circumstances, creating an even more serious dire hazard.
Disagreement among people affected by this issue means that it’s necessary to be able to cite actual research.
Reports on FPE Equipment Defects:
- “Status Report- Evaluation of Residential Molded Case Circuit Breakers”, Wright-Malta Corp, (For US Consumer product Safety Commission, Project# CPSC-C-81-1455), August 10,1982 (Contains analysis of mechanism of failure of FPE two-pole Stab-Lock breakers).
- “Failure Analysis of Residential Circuit Breaker Panel”, Wright-Malta Corp, (For US Consumer product Safety Commission, Project #CPSC-C-81-1455), May 20, 1982 (Contains failure analysis of FPE Stab-Lock panel that ignited due to failure of buss-bar interconnections in the backside of the panel.)
- “Phase II Report, Evaluation of Residential Molded Case Circuit Breakers”, Wright-Malta Corp,,(For US Consumer product Safety Commission, Project# CPSC-C-81-1455), March 10, 1984 (Contains experimental analysis of materials, construction, and performance of molded case circuit breakers, including FPE. Lack of corrosion resistance of certain internal parts is considered to be a factor in the failure of the circuit breakers.)
- “Final Report: Calibration and Condition Tests of Molded Case Circuit Breakers,” Wright- Malta Corp,(For US Consumer product Safety Commission, Project #CPSC-C-81-1429), December 30, 2981 (Extensive calibration and functional testing of FPE breakers. Substantial percent failures to trip an overload).