Demystification of Arc-Fault Circuit-Interrupters (AFCIs) – Part II: Technology and Applications

Residential fires of electrical origin have been a major concern for a long time. A fire can be initiated by excessive current (due to an overload or a short circuit), or arcing current. Therefore, both Canadian Electrical Code (CE Code) Part I and the National Electrical Code (NEC) require the installation of overcurrent protection devices (OCPDs) to detect and clear excessive current. Conversely, arcing current is too low for OCPDs to detect. It could take an electric arc, minutes, days, weeks, months, or even years to initiate a fire. Therefore, a new solution was required for detecting those slowly developing arcs. Thus, Arc-fault Circuit-Interrupters (AFCIs) were born. AFCIs are capable of detecting an arcing condition (while still developing) and de-energizing the circuit before the arcing circuit ignites, AFCIs have been a hot topic creating quite a bit of controversy in the recent NEC review cycles. It is the authors' opinion that this controversy stems from a lack of clear understanding of AFCIs operation, available technologies, and their capabilities. This paper is the second of two papers attempting to add clarity and avoid the confusion surrounding AFCIs, their applications, and success in making an impact on home electrical fires.