Electrical Fire Prevention - Section 210.12 of the NEC

book_insights.pngThe story of the arc fault circuit interrupter (AFCI) is an interesting one as it is technical in nature, wrapped in controversy, fueled by passion, and delivers a positive electrical safety impact to the electrical industry. The 2014 National Electrical Code® (NEC) again modified Section 210.12, expanding AFCI coverage and providing more options. When you open your code book to Section 210.12 this year, don’t let the size of the section intimidate you. It’s not all that big of a change.

From an NEC perspective, it was during the NEC 1996 development process that the need for this technology was identified to the electrical industry through the NFPA 70 development process. Proposal 10-97 brought forth the following proposed language:

“Section 240-83 (f) Circuit Breakers In Dwelling Units. (New title & text.) Circuit breakers for 15A and 20A branch circuits supplying receptacles in living and sleeping areas of dwelling units, in accordance with Section 210-20 (b), shall be listed and shall be marked ‘LIT’ (low instantaneous trip).”

The submitter shared Consumer Products Safety Commission (CPSC) data of fire statistics and study information that was used as the foundation for the work that Code Making Panel (CMP) 2 continues to this day. The submitter of this proposal was seeking to achieve the goal of arcing fault protection noting in the substantiation that, “Evidence exists that present safety standards and national codes do not adequately address the risk of fire resulting from arcing shorts in branch circuits, fixture wiring, extension cords, and power supply cords (i.e., the power supply system).”

The panel rejected this proposal with a panel statement that, “The substantiation included with the proposal is insufficient to show that lowering the instantaneous trip levels will adequately address fires due to low level arcing faults in damaged appliances and extension cords. A more complete analysis of cord problems and alternate solutions, such as alternate cord constructions, supplemental overcurrent protection, reduced appliance inrush, and electronic sensing means is needed. Mandating these lower instantaneous trip levels will result in a false level of security from arcing faults. The submitter has not provided any compelling evidence to show that existing branch circuit overcurrent protection devices do not protect premises wiring as required in Article 240.”

In the historical documents around this topic, it is quite clear that the molded case circuit breaker, listed to UL Standard 489, “Molded-Case Circuit Breakers, Molded-Case Switches, and Circuit- Breaker Enclosures,” was under the microscope; in some cases identified as devices that are not performing as they should. The electrical industry, including manufacturers, standards developers, and other experts, began the process to create the standard for the device that would address the identified problem, the electrical fire. The process included more studies, research, and fire data, and the final product is what we know today as UL 1699 “Arc-FaultCircuit-Interrupters.” You can trace the origins of this UL standard to 1997, shortly after the code panel debates and introduction of the electrical fire problem to the electrical industry.

Important lessons can be learned as a result of the debates around this topic. Many people thought, and probably some still do today, that a standard thermal magnetic circuit breaker protects all wire in the circuit from all types of faults, even those wires that are plugged into receptacles. Some that are quite familiar with the NEC will point out Section 210.20, “Overcurrent Protection,” which states, “Branch-circuit conductors and equipment shall be protected by overcurrent protective devices that have a rating or setting that complies with 210.20(A) through (D).” This section has to be read in its entirety to understand