Demystification of Arc-Fault Circuit-Interrupters (AFCIs) – PART I: Beginning of the Odyssey

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 (AFCls) were born. AFCls are capable of detecting an arcing condition (while still developing) and de-energizing the circuit before the arcing circuit ignites. AFCls 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 AFCls operation, available technologies, and their capabilities. This paper is the first of two papers attempting to clarify the confusion surrounding AFCls, their applications, and success in making an impact on home electrical fires.