Home Circuit Protection

There's nothing like trying to plug-in an appliance and being unable to find a grounded outlet.  Teaching myself to be a do-it-yourself electrician, I spent a Saturday replacing the two slot electrical outlets in my home with grounded three slots.  Luckily, I found the non-metallic (NM) wire (I'm trying to sound like an electrician) contained three wires.   The black wire is hot, the white is neutral and a third (either bear or sheathed in green) is the ground.   So my work was limited to connecting the new three slot grounded receptacle to the grounding wire.

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Bringing old houses up to modern electrical standards can be a challenge since it wasn't until the 1960s that electrical codes requiring grounding wires began to be enforced.  And if interior partitions aren't being stripped to their studs, fishing new wire can be challenging.  Code allows for original ungrounded wiring is to remain in place as long as protection from electrical shocks and fire is provided by Ground Fault Circuit Interrupter (GFCI) and Arc-Fault Circuit Interrupter (AFCI) outlets and/or breakers.

Everyone is probably familiar with GFCI protection.  These are the outlets and breakers with reset buttons.  You typically find the outlets in bathrooms, kitchens, laundries and exterior locations.  But now codes are beginning to require a new type of protection, AFCI.  Here's my research on what the difference is between the two and why they are both important in protecting the homeowner.

Ground Fault Circuit Interrupter (GFCI)

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GFCIs when installed at outlets or breakers are designed to protect against electrical shock.  They measure the current passing through the black "hot" wire and returning through the white "neutral" wire.  Typically, there should be no difference in current. If there is a difference (it can be as little as 0.004 amps), the outlet will trip.  In other words, within milliseconds, the outlet opens the circuit before the unaccounted for current passes through a person causing an electrical shock.

The current National Electrical Code (NEC) requires GFCI outlets or protected circuits at bathrooms, kitchen countertop surfaces, garages, outdoor areas, unfinished basements, and laundry areas.  Code also allows them to replace outdated two slot receptacles since their operation is uneffected by leaving the ground unconnected.

Arc-Fault Circuit Interrupter (AFCI)

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AFCIs when installed at outlets or breakers are designed to protect against fires.  AFCIs  are programmed to monitor current waveform characteristics.  If the current waveform matches the characteristic of a parallel or series arcing fault, the circuit is opened.  If left undetected, electrical arcs can generate heat within wire, even sparks which can ignite adjacent combustible materials.  Arcing faults typically occur inside walls, where damaged wires are left unseen.

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The current Michigan Electrical Code only requires AFCI protection at bedrooms.  However, if the State adopts the latest version of the NEC, AFCI outlets or protected circuits will be required at basically every remaining room: family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets and hallways.

Fire Prevention Facts

Though GFCIs have gained universal acceptance, expansion of AFCI requirements in the latest NEC has proven more controversial.  But the facts remain, between 2003 and 2005:

• Annually, an estimated 28,300 residential building electrical fires caused 360 deaths, 1,000 injuries, and $995 million in direct loss.
• Fifteen percent of residential building electrical fires started in bedrooms.
• Nearly half (47%) of the residential building electrical fires where equipment was involved were caused by the building’s wiring.
• Twenty-two percent of residential building electrical fires occurred during December and January.

Time will tell if new AFCI code requirements prove effective in protecting the public from electrical fires.

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"Understanding the NEC Requirements for GFCI and AFCI", Mike Holt's Illustrated Guide to Understanding the National Electrical Code, Volume 1.

"Residential Building Electrical Fires", U.S. Department of Homeland Security, U.S. Fire Administration

National Fire Data Center,  Topical Fire Report Series, Volume 8, Issue 2 / March 2008.