What is Ground Fault Circuit Interrupting (GFCI)?
GFCI protection helps prevent shock or electrocution of people, especially in areas like kitchens, bathrooms, outdoors and in basements, where people are more likely to become a path to ground via plumbing fixtures, pipes, or damp floors that are in contact with earth or pipes. GFCI’s may also provide alternative safety for outlets lacking equipment grounding facility. Where the equipment ground would draw short-circuit current through the circuit breaker causing it to trip, the GFCI senses and interrupts resistive shorts from 6 milliamps and higher, making it more effective for personnel safety than the equipment ground it ‘replaces’ (see ‘Retrofit applications’, below).
GFCI’s open (turn off) a circuit in a fraction of a second, when current flowing to a load (ie: receptacle) is not balanced precisely on both wires supplying the load. Imbalances on the wires indicate unintentional current flow, for example, from a short inside a hair-dryer or washing machine, through a person touching the cord-and-plug appliance, and to ground via an accidental ground path, such as a faucet handle and/or copper plumbing pipes. Such a ‘ground fault’ may pass less than one amp of current through the person being shocked (failing to trip any breaker), and yet be sufficient to prevent the person from letting go of what is shocking them. Without operation of a GFCI protective device (set to trip when unbalanced current exceeds 6/1000 of one amp — ie: 6 milliamps), the person being shocked can become more and more nervous and sweaty, increasing skin moisture and conductivity until current steadily increases (but remains well below the 15- or 20-amp trip threshold of the circuit breaker), and conductivity in the victim’s body may extend along sweaty arms to the heart and trigger a fatal heart attack (electrocution).
Conventional circuit breakers protect buildings from fire; GFCI’s protect people from shock. Operating normally, a 20A breaker typical of circuits supplying bathrooms or kitchen counter receptacles may carry 100A of current for a minimum of 5 seconds and a maximum of 20 seconds. That’s more than 10,000 Watts of power flowing, for long enough to say ‘Ouch!’ more than a couple times (this is assuming your vocal cords aren’t being fibrillated).
The National Electric Code (NEC) governing electrical installations changes every three years, and GFCI devices have not always existed. Some locations where protective devices are required for new construction are ‘grandfathered’ in existing construction. Philadelphia housing code (for rental properties) and prudence (for others) mandates installation of GFCI protection at locations where the NEC requires it.
GFCI Receptacles in Retrofit Applications
GFCI receptacles may be installed on any safe circuit, whether grounded or not — so long as the receptacle’s wiring enclosure has enough room to accommodate the bulk of the GFCI device, most of which sits recessed inside the box. Many older circuits can benefit from GFCI-protection. These include:
- Older kitchen circuits that pre-date GFCI technology, whether the circuits have equipment grounding facility or not.
- Old circuits with no equipment grounding facility, where personnel safety modes equivalent to or better than equipment grounding may be desired as a retrofit alternative that does not require new wiring.
See other video illustration and demonstrations at ElectricMonk TV
Off-site Links ->
- Annapolis Home Inspection, LLC Aluminum branch circuits, homes 1965-1972
- ComplianceAndSafety.com OSHA Electrical Safety Training
- Electric Monk TV (YouTube) Video channel for PhillyLicensedElectrician.com Robert Monk
- EnergyConservation HowTo A tinkerer genius discusses energy conservation and his ladder system for accessing the attic (where a lot of energy-saving work happens).
- PennFuture Energy Center Energy and energy efficiency news for the Commonwealth of Pennsylvania
- Phila area rife with building efficiency upgrade opportunities Philadelphia Inquirer article discusses recent study showing Philadelphia’s inner-ring suburbs stand to save from energy conservation retrofits.
- Philadelphia Row-house Manual A design, maintenance, and modifications manual for our most widely-used form of housing.
- Robert Monk Robert Monk’s personal blog
- SolarCities (DOE) Solar PV Levelized Cost Interactive Comparator Simple graph compares ‘levelized cost’ of energy from solar PV to conventional grid rates, with a time-slider interactive feature.
- The Circuit Detective – Solve Home Electrical Problems Yourself! Electrical troubleshooting procedures pitched to homeowners.
- The Energy Co-op Blog from a leading alternative energy provider in PECO territory, includes fun conservation tips.
- Weatherization: the anti-Solyndra Salon.com article praising the continued success of the federal Weatherization Assistance Program (WAP), low-income energy-savings and job-creation.
- West Philly Tool Library Official site of WPTL, Philly’s own community tool lending library: like a book library, but tools!
- WestPhillyLocal .com Site name say sit all.
- Bartram's Gardens Founded in Philadelphia’s colonial era, today the gardens continue pioneering in horticulture and agriculture with a variety of herbs, trees and other vegetation in an arboretum/gardens on the Schulkill River banks, and a new farm abutting sadly neglected
- HiddenCity Philadelphia Surprising places it takes an adventurer to discover; events, too.
- Philly Household Hazardous Waste Drop-off Schedule City of Philadelphia dates and places for disposing of spent batteries, CFL lamps, unused paint and cleaning products, etc. LovePhilly: don’t pour these in the drain or send them out with the trash.
- Reading Terminal Market Purveyors of fine foods and foodie stuff, all under one roof downtown under the PA Convention Center
- Secret Garden on the Rails Jacques-Jean Tiziou shows some dramatic natural and urban and naturalized-urban scenes along abandoned rails of Philadelphia
- Sketch Burger, Fishtown A vegan-friendly burger joint with a #1 in Philly contender beef burger, best fries that somehow stay fresh for 1/2 hour while you tackle burger, and a vegan cafe vibe of friendly folks.
- WXPN: Philly sings in key of love Love songs by Philly artists