Home wiring - electrical wiring safety

Engineers examine aged wiring systems in abandoned homes for clues about electrical fires  

A different kind of harvest is underway in Alabama and the Midwest. Engineers are reaping the wiring and electrical components from older houses to see how these materials have aged during the 100 years that electricity has become a mainstay in American homes.

"The question we seek to answer is, why is there a residential electrical fire problem in the United States when we have such a good electrical code?" said Kathleen Almand, P.E., executive director of the Fire Protection Research Foundation in Quincy, Mass., which is overseeing the Residential Electrical System Aging Research Project.

Each year, electrical distribution systems and lighting equipment are involved in an estimated average of 32,000 home fires reported to U.S. fire departments. On average, these fires cause 950 injuries, 220 deaths and nearly $674 million annually in property damage per year, according to the National Fire Protection Association.

With one-third of U.S. housing - some 30 million homes - built more than 50 years ago, it seemed logical to examine the ravages of time on wires, connectors and outlets in looking for patterns in the causes of electrical fires.

"This is an important project and one that's never been done before," said John Drengenberg, Consumer Affairs Manager for Underwriters Laboratories (UL). "Residential electrical systems are seldom inspected after they are installed and they tend to be destroyed in house fires."

UL, the independent product safety testing and certification organization, is a sponsor of the Residential Electrical System Aging Research Project. UL is also responsible for testing the wires, connectors, outlets and switches "harvested" from the abandoned house walls.

Engineers at UL's headquarters in Northbrook, Ill., are comparing durability in various wiring technologies that were cutting edge in their day. The results will provide critical information to code writers, both in the electrical and fire protection arenas.

The goal of the $412,000 Residential Electrical System Aging Research Project is to have samples harvested from 100 homes scheduled for demolition throughout the United States by late 2007. So far, 10 homes in Alabama, northern Illinois and Wisconsin have been harvested. These homes were built in the 1920s, '50s, '60s and '70s.

"The good news is that electrical systems are robust. They'll take a pretty good beating and hold up," said Donny Cook, chief electrical inspector for Shelby County, Ala., and a harvester for the study.

But homeowners should not assume all is well simply because their fuses aren't blowing or they're not receiving shocks or smelling burning plastic, Cook warned. "It's worth the effort and a little bit of money to have these older electrical systems inspected."

Unseen hazards

Inside the walls, wire insulation could be cracking and crumbling, especially if the wires are drawing more current than they were designed to handle. Or the wood frame above the plaster ceilings might become charred by light bulbs that are too close to the ceiling or higher in wattage than the light fixture's rating.

"Those things could be happening, but because the light still burns and the vacuum still works, everything seems to be functional," Cook said. "Then that one magic moment comes when your home catches fire."

To avoid such hazards, consumers should understand the limits of their wiring systems. Some of this will depend on when the home was built or if the electrical system was upgraded, but in other cases telltale signs can predict that something is wrong.

"Anytime you receive a shock from an electrical appliance, outlet or wall switch in your home, it's a warning sign that you may need to talk with a qualified electrician," Drengenberg said. "If a fuse blows or a circuit breaker trips right after you replace or reset it, there's a problem somewhere. Flickering or dimming lights could mean loose connections, overloaded circuits, improper wiring or arcing and sparking inside the walls."

Older homes may have newer wiring systems, but the era when that wiring was installed and how well it was installed will have bearings on a home's electrical limitations. Before buying a home, especially older homes, have someone certified in electrical work inspect the electrical system. Contact the National Association of Certified Home Inspectors for referrals.

Know your home

Electrical capacity is a major concern with older wiring systems. Homeowners in the 1930s didn't have a lot of electrical appliances, except for maybe a few lights and a radio, which didn't require a lot of juice. That started to change in the '40s and '50s, but then the popularity of air conditioning in the '60s and '70s rendered many mid-century electrical systems obsolete. Even homes built as little as 20 years ago might have insufficient power for today's entertainment and personal computer systems.

"If your TV or computer screen wavers whenever another appliance is turned on, you might need additional electrical capacity," Drengenberg said.

In older homes, a sign that you are drawing too much current through your electrical outlets is heat. "If your receptacles or plugs are hot to the touch - you can't keep your hand on them for more than five seconds - you may have an overload," Drengenberg said.

When too much current is drawn through the wires, the wires heat up, baking the insulation and eventually destroying it. Wire with damaged, decayed or brittle insulation can lead to shocks and fires.

Another issue with older home wiring systems is the number of receptacles in each room. Today's electrical code requires that outlets be placed every 12 feet of running wall space, about one per wall in the average 10-by-12-foot room. Houses built before 1956 were required to have outlets placed every 20 feet and homes built before 1935 weren't required to have wall outlets at all.

"Too many appliances plugged into a single outlet could mean that your house does not have a sufficient number of receptacles," Drengenberg said. "Relying on extension cords is not the answer. Extension cords are meant for temporary use only and should not be a substitute for permanent wiring."

Homeowners also should be aware that electrical code enforcement is the responsibility of local government, be it state, county or municipality. Some areas of the country don't require electrical inspection when a home is built, nor do they enforce national electrical codes during that construction. Others places started electrical code enforcement as little as 20 years ago. To learn whether your community has electrical inspectors and how long electrical codes have been enforced there, start by contacting your local governing board.

Importance of grounding

Finally, there is the issue of grounding. Grounding prevents painful or even deadly electrical shocks when electricity flows through an improper path. Every home electrical system should have some type of grounding ability.

Newer homes are wired with cables that include a ground wire. The ground wire allows for the use of the three-pronged receptacles that are needed to power certain appliances, particularly ones with metal shells, such as refrigerators and washing machines.

Many wiring systems installed in the 1950s and earlier used non-metallic wiring, which lacked a ground wire. Homes from this era have only two-pronged outlets, unsuitable for many modern conveniences. Simply replacing two-pronged receptacles with three-pronged receptacles is a violation of the National Electrical Code® if there is no ground path present.

Around 1970, ground-fault circuit-interrupter (GFCI) protection was added to the electrical code. Found mostly in areas where people are likely to be outdoors or near water - swimming pools, bathrooms, garages, basements, kitchen countertops - GFCI protection is designed to trip before a deadly electrical shock can occur. Just 25 years after the GFCI was introduced, the number of accidental electrocutions in the United States had been cut in half, even though electricity use had doubled.

The most recent electrical protection technology added to the NEC® occurred in 2002, when the arc-fault circuit-interrupter (AFCI) circuit-breaker was required for bedroom outlets. Bedrooms were selected because of their history of electrical fires.

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