Dear Inspector,

This month we will discuss Arc-Fault Circuit Interrupters. These devices are new in the National Electrical Code in 1999, but the implementation was set for 2002. We will start seeing them in new homes once jurisdictions begin adopting that version of the NEC. I expect some controversy over these devices as the NAHB is protesting the use of them claiming the requirement will just raise the cost of housing for the public. Arc Fault Circuit Interrupters (AFCI) cost about $25 to $40 each.

AFCI devices look similar to GFCI breakers. However, they do not protect persons from electrical shock, they protect against electrical fire. The insurance industry was instrumental in the inclusion of AFCI devices in the code, as a means of reducing the damage to persons and property from electrical fires.

An arc is current jumping from one conductor to another. Sometimes this arcing is harmless, such as the arcing that might occur at a wall switch when we operate it. On the other hand, an arc fault is arcing that continues to sputter and re-strike. Arc faults can produce very high temperatures at low currents that would not trip an ordinary breaker. When an arc fault occurs without contact, such as across a nonconductive material or through the air, fire can occur. Arc faults often occur in old frayed extension cords and lamp cords and in old or damaged wiring. Many of these are used in bedrooms, and hidden by drapery, bedding, carpet, etc. For this reason the new Code requirement specifies AFCI's only on bedroom circuits.

The AFCI works by monitoring the wave pattern of the voltage and current in the circuit. When the pattern resembles that consistent with an arc fault, the device de-energizes the circuit in a manner similar to a GFCI device. The AFCI circuitry is somehow designed to determine the difference between a normal contact arc (such as at a switch or when quickly removing a cord from a receptacle) and an abnormal arc described above. There is a test button on an AFCI, similar to a GFCI device. However, testing the AFCI will de-energize the entire circuit, leaving all digital components blinking at the occupants. Testing AFCI devices is not required by any home inspection society standards of practice I have read, so testing would be considered above standards. Personally, I would not test them. Well, maybe if the house was vacant……

Mike Casey
Kaplan Professional Schools
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