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Can the AFCI be used in retrofit applications in older dwellings that use 2-wire circuits without a grounding conductor?

Yes. The Branch/Feeder AFI (circuit breaker type) is good protection for 2-wire circuits. It provides for detection of a low-level short circuit of 75 amperes or above that would not be detected by an overcurrent protective device. It also provides detection of an arcing ground fault occurrence of 5 amperes or above. Note that the Square D AFCI actually detects arcing ground fault of 50 milliamperes and above. This protection is as valid in 2-wire circuits as in 3-wire circuits that include the grounding conductor. The difference is that with the added grounding conductor in the 3-wire circuit, an arc of any level may reach the grounding conductor and be detected at levels below 75 amperes, which provides a degree of protection not available in 2-wire circuits.

CTA-ID : 10009
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