"An appliance plug damaged by impact repeatedly caused tripping of the AFCI until the problem was discovered. When the appliance cord was replaced, no further tripping of the AFCI occurred.
n A room air conditioner that had developed a defect tripped the AFCI. The performance of the AFCI was questioned until the offending appliance was discovered and disconnected. The AFCI continues in service with no further tripping.
n An AFCI installed in a new building tripped repeatedly until damage caused by a nail through insulation was discovered and corrected.
n An AFCI installed as a retrofit in an older building tripped as soon as it was turned on. The installing electrician found the problem with extensive evidence of arcing in an old lighting fixture.
n Another damaged lamp with line-to-ground arcing was found when an AFCI was installed in an existing circuit. The AFCI tripped when the circuit was first energized after the installation.
n An AFCI tripped when retrofitted into an existing circuit. Examination of the circuit disclosed that wire insulation had burnt back exposing bare conductors near their connection to a receptacle. The exposed wires had been arcing through the charred insulation. It appeared that heat from a loose connection at the receptacle had caused the wires to burn back.
As you might guess from that list, the greatest number of fires from electrical causes is in homes ten years old and older where changes have been made to electrical circuits by various owners and where insulation is deteriorating with age, use and misuse. However, fires from electrical arcs are recorded for residences of all ages. Besides, all homes become older homes. If the protection is not present before they age, they will remain unprotected as they age." full story at:
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