Short Circuits: Old Wiring Could Be Hazardous

Residential electrical wiring changed during the 20th century as new appliances appeared on the scene and electricity evolved from a luxury to a mainstay. More appliances at home led to safety improvements and an increased number of room outlets, leaving older home wiring to play catch-up. Although most older home electrical systems have been upgraded over the years, safety shortcomings may still exist. Since a third of American homes were built more than 50 years ago, home buyers and folks living in older homes should be aware of how wiring changed during the last century.

Electric capacity is a major concern with older wiring systems. Homeowners in the 1930s didn’t use a lot of electrical appliances, except for a refrigerator, a few lights, and a radio.

An explosion of appliance purchases followed in the late 1940s and early ’50s. But the arrival of air conditioning during the 1960s soon rendered many mid-century home electrical systems obsolete. More recently, residences built as little as 20 years ago might be insufficient for handling entertainment systems and personal computers.

Each year, household wiring and lighting cause an estimated average of 32,000 home fires. On average, these fires result in 950 injuries, 220 deaths, and nearly $674 million in property damage, according to the National Fire Protection Association.

“Residential electrical systems are seldom inspected after they are installed and tend to be destroyed in house fires,” explains John Drengenberg, consumer affairs manager for Underwriters Laboratories, Inc., (UL), an independent product safety testing and certification organization based in Chicago, Ill.  “Homeowners should not assume all is well simply because fuses aren’t blowing, circuit breakers tripping, or they’re not receiving shocks or smelling burnt plastic. Inside the walls, wire insulation could be cracking and crumbling, especially if wires are drawing more current than they were designed to handle. The wood frame above plaster ceilings could also become charred by lightbulbs that are too close to the ceiling or higher in wattage than the light fixture’s rating.”

To avoid such hazards, consumers should understand the limits of home wiring systems. Often, this depends on when a home was built or if the electrical system was upgraded. In other cases, though, telltale signs may indicate a problem.

“Anytime you receive a shock from an electrical appliance, outlet, or wall switch in your home, it’s a warning that you should talk with a qualified electrician,” Drengenberg cautions. “If a fuse blows or a circuit breaker trips right after you replace or reset it, you have trouble somewhere. Flickering or dimming lights could mean loose connections, overloaded circuits, improper wiring, or arcing and sparking inside walls.”

In older homes, heat means too much electrical current’s being drawn through outlets. “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 advises.

When too much current gets drawn, wires heat up, baking and eventually weakening the insulation. Wires with damaged, decayed, or brittle insulation can lead to shocks and fires.

Another issue associated with older home wiring systems is the number of receptacles in each room. Today’s electrical code requires 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, while homes built before 1935 weren’t required to have wall outlets at all.

“Relying on extension cords is not the answer,” indicates Drengenberg. “Extension cords are meant for temporary use only and should not be a substitute for permanent wiring.”

Proper grounding, meanwhile, prevents painful or even deadly electrical shocks when electricity flows through an improper path. Every home electrical system should have some type of grounding.

Newer homes are wired with cables that include a ground wire. The ground wire allows for use of three-pronged receptacles 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 boast only two-pronged outlets, unsuitable for many modern conveniences. Simply replacing two-pronged receptacles with three-pronged receptacles violates the National Electrical Safety Code if no ground path exists.

In some cases, older homes may feature newer wiring systems. But the era when the wiring was upgraded impacts electrical limitations. Before buying a home have someone certified in electrical work inspect the system to be safe. Visit for referrals.

Source: Underwriters Laboratories, Inc.

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