Wiring Issues for Smoke Detectors

Basic Smoke Detector Wiring

• The wiring of a smoke detector system is based on a shared circuitry connected to the main electrical power supply in your home. A feeder cable that draws electricity from the power supply and supplemental ground and circuit-connecting cables, known as traveler cables, provide electrical current, shared grounding, and interconnectivity between all smoke detectors in your home. This basic wiring diagram includes the necessary power as well as safe ground wiring to prevent "dead shorts", which are improper circuit wiring that presents both a shock and a fire hazard.

Faults and Wiring Issues

• Problems occur in electrical wiring when the circuit is shorted out by either a faulty ground connection or by electricity jumping from one wire to the other, known as an arc. Both can be caused by a lack of sufficient insulation around the wiring and the connections at installation, or by subsequent damage to the wiring after installation. Both ground faults and arc faults cause the electrical current to be misrouted, resulting in a failure of smoke detectors as well as a potential fire hazard.

Fault Circuit Interrupters

• Wiring circuitry has been developed to include ground fault circuit interrupters (GFCI) and arc fault circuit interrupters (AFCI), which prevent against shock and fire hazards when grounds and arcs occur. Fire and building codes concerning GFCI and AFCI are wiring issues to consider when installing home smoke detectors. The National Fire Alarm Code (NFAC) and the National Electrical Code (NEC) both require circuit interrupters to be included in a home wiring system, but these technologies do have an effect on the installation of smoke detectors. As of 2005, smoke detectors cannot be installed on wiring using GFCI protection unless the entire home has this technology built into the main circuit from the power supply. Additionally, all circuits that provide power to the bedrooms must have AFCI protection, including smoke detectors wired to the same branch circuit.

Interconnectivity Issues

• Fire safety and electrical codes as of 2010 require smoke detectors to be both hard-wired to the electric current of your home and to be connected together. This interconnectivity is a good idea, because if one detector's alarm goes off then all the other detector alarms in the system will be activated. However, a power outage or a circuit breaker being tripped will result in a deactivation of the smoke detectors. Although a circuit used only for the smoke detectors-known as a dedicated circuit-will protect against other circuit breakers in the house being tripped, it will not protect against power outages. Fire safety and building codes, such as the NFAC and NEC, recommend smoke detectors with a battery back-up to be used in case of a loss of power to the electrical current.