Typical arc-fault breaker

Arc Fault Circuits

The “AFCI” is an arc fault circuit interrupter. AFCIs are newly-developed electrical devices designed to protect against fires caused by arcing faults in the home electrical wiring. In Nashville/Davidson County and most municipalities in Williamson Counts such as Brentwood, Franklin, Nolensville and Spring Hill, these devices have been required since 2002.

THE PROBLEM

Annually, statistics show that over 40,000 fires are attributed to home electrical wiring. Fires resulting in over 350 deaths and over 1,400 injuries occur annually. Arcing faults are one of the major causes of home fires. When unwanted arcing occurs, high temperatures caused by the electric current can ignite nearby combustible materials such as dust, wood, paper, and carpeting. Faults sometimes occur in damaged or deteriorated extension cords or plugs. Other causes can be puncturing of wire insulation from picture hanging or cable staples, poorly installed outlets or switches, extension cords caught in doors or under furniture, furniture pushed against plugs in an outlet, natural aging, and cord exposure to heat vents and sunlight.

HOW THE AFCI WORKS

Conventional circuit breakers only respond to overloads or short circuits; so they do not protect against arc conditions that can produce erratic current flow. The breaker is selective so that "normal" arcs do not cause it to trip. The circuitry continuously monitors current flow through the device and use unique current sensing circuitry to discriminate between "normal" and unwanted arcing conditions. When an unwanted arcing condition is detected, the control circuitry in the device trips the internal contacts, thus de-energizing the circuit and reducing the electrical potential and chances for a fire. Although designed to react to situations that can cause a fire, they will not and cannot eliminate them altogether.

WHERE AFCIs SHOULD BE USED

The 1999 edition of the NEC (National Electrical Code), the model code for electrical wiring adopted by many local building jurisdictions, requires AFCI devices for receptacle outlets in bedrooms, effective January 1, 2002. Although the requirement is limited to only certain circuits in new residential construction, AFCI’s should be considered for added protection in other circuits and for existing homes as well. Older homes with aging and deteriorating wiring systems can especially benefit from this added protection. In this area, these are required by most municipalities whenever upgrading a panel box.

INSTALLING AFCI’s

AFCI circuit breakers should be installed by qualified electricians. In homes equipped with conventional circuit breakers rather than fuses, an AFCI circuit breaker may be installed in the panel box in place of the conventional circuit breaker to add arc protection to a branch circuit. Homes with fuses will need to add a branch circuit box capable of handling AFCI devices. 

TESTING AFCI DEVICES

AFCI’s should be tested after installation to make sure they are working properly and protecting the circuit. Subsequently, AFCIs should be tested once a month to make sure they are working properly and providing protection from fires initiated by arcing faults. In some building jurisdictions, all lighting and wall circuits should be de-energized.

A test button is located on the front of the device. If the device does not trip when tested, the breaker is defective and must be replaced.

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Typical GFCI circuit with test buttons in the middle

Ground Fault Circuits

A GFCI is an inexpensive device designed to protect people from severe or fatal electric shocks should they become or interrupt a path to ground. It is estimated that the installation of this device could prevent over two-thirds of the approximately 300 electrocutions still occurring each year in and around the home. Studies also estimate that the installation of these devices could also prevent thousands of burn and electric shock injuries each year.  

A common misconception concerning GFCI devices is that they must have a path to ground in order to operate. GFCI devices work on current differential. In other words the circuitry “senses” the current leaving the device and the amount of current returning back to the device. If there is more than a 5 milliamp (0.05A) differential, the device will de-energize. This the reason that you can use a GFCI outlet on an older style 2 wire circuit commonly found in older properties built before 1970. 

The NEC (National Electrical Code) now requires GFCI protection for receptacles located outdoors; in bathrooms, garages, kitchens, crawl spaces and unfinished basements; and at certain locations such as near swimming pools. A combination AFCI and GFCI can be used to satisfy the NEC requirement for GFCI protection only if specifically marked as a combination device.

THE PROBLEM

An unintentional electric path between a source of current such as an outlet or lighting fixture and a grounded surface such as a water pipe or fixture is referred to as a "ground-fault." Ground faults occur when current is leaking somewhere from the energy source to the ground. How and where this energy leaks is very important. If your body provides a path to the ground for this leakage, you could be injured, burned, severely shocked, or electrocuted. Keep in mind that it takes a very small amount of current, 30 milliamps (0.30 amps) at 110 VAC to stop your heart! 

COMMON DEVICES

There are four common types of ground fault circuit interrupters available for home use:

RECEPTACLE TYPE

This device is used in place of the standard duplex receptacle found throughout the house It will fit into the standard outlet box and gives protection from "ground faults' whenever an electrical product is plugged into the outlet or an unusual path to ground is detected. Most receptacle-type GFCls can be installed so that they also protect other electrical outlets further "down stream" in the branch circuit. NEC does not dictate the number of downstream outlets on a GFCI circuit. This is determined by the manufacturer. Typically 4 – 7 outlets is the norm.

CIRCUIT BREAKER TYPE

In homes equipped with circuit breakers rather than fuses, a circuit breaker GFCI may be installed in a panel box to give protection to selected circuits. These can be either 110VAC such as in the “standard” outlet circuit, or 220 VAC for hot tubs and similar applications. This device serves a dual purpose - it will shut off electricity in the event of a "ground-fault," and it will also trip when a short circuit or an over-load occurs. This dual protection covers the wiring and the devices being served by the branch GFCI protected circuit.

PORTABLE TYPE

Where permanent GFCl protection is not practical, portable GFCl devices may be used. One type contains the GFCI circuitry in a plastic enclosure with plug blades in the back and receptacle slots in the front. It can be plugged into a receptacle, then; the electrical product is plugged into the GFCI. Another type of portable GFCI is an extension cord combined with a GFCI. It adds flexibility in using receptacles that are not protected by permanent GFCl devices.

GFCI SWITCHES

These devices are in-line devices used around wet locations. The GFCI circuitry fits in a plastic enclosure and will have the trip and reset buttons only.  This will fit in a standard outlet boxes. Typical applications are in bathrooms and other wet areas were GFCI protection is needed. Whirlpool tubs, shower lighting, basement/crawlspace lighting are typical applications for this device.

INSTALLATION GUIDELINES

In homes built to comply with NEC (National Electrical Codes), GFCI protection is required for most outdoor receptacles (since 1973), bathroom receptacle circuits (since 1975), garage wall outlets (since 1978), kitchen receptacles (since 1987), and all receptacles in crawl spaces and unfinished basements and other damp locations (since 1990). Keep in mind that many building jurisdictions did not follow these guidelines and many properties may not have these devices.

Owners of properties that do not have GFCl devices installed in all those critical areas specified in the latest version of NEC should consider having them installed. For homes protected by fuses, you are limited to receptacle or portable-type protection and these should be installed in areas of greatest exposure, such as the bathroom, kitchen, basement, garage, and outdoor circuits.

A GFCI should be used whenever operating electrically powered garden equipment (mower, hedge trimmer, edger, etc.). Consumers can obtain similar protection by using GFCIs with electric tools (drills, saws, sanders, etc.) for do-it-yourself work in and around the house. 

Do not plug freezers and refrigerators into GFCI outlets in garages. Sometimes eddy currents generated by the compressor motors “trick” the GFCI device into a fault situation. These appliances should be plugged into a single outlet dedicated circuit. 

TESTING GFCI DEVICES

• All GFCI devices should be tested once a month to make sure they are working properly and are protecting you from fatal shock. GFCIs should be tested after installation to make sure they are working properly.

• To test the receptacle GFCI, first plug a nightlight or lamp into the outlet. The light should be on. Then, press the "TEST" button on the GFCI. The GFCI's "RESET" button should pop out, and the light should go out.

• If the "RESET" button pops out but the light does not go out, the GFCI has been improperly wired. Contact an electrician to correct the wiring errors.

• If the "RESET" button does not pop out, the GFC1 is defective and should be replaced.

• If the GFCI is functioning properly, and the lamp goes out, press the "RESET" button to restore power to the outlet. 

• A test device can be purchased at most home improvement stores for a few dollars to test the "downstream" outlets protected by the master device.

For other testing guidelines and information from Underwriters Laboratories click here.

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