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Home Wiring System

 

Home Wiring System

More than 30 million homes, or about one-third of the homes in the United States are at least 50 years old, and studies have shown that the frequency of fires in these aging homes is disproportionately high. Many older homes were built with electrical systems and components which are no longer safe and may be considered as fire hazards.

Fire and other electrical safety concerns may arise due to aging, improper installation and alteration, or misuse. It is important to identify what type, color, and size wire is needed in order to properly address hazardous situations before they become critical.

Knob & Tube Wiring: 1800s–1930s

Knob and tube wiring was designed as an open air system that used ceramic knobs to separate wires from combustible framing. These suspended wires were directed through ceramic tubes to prevent contact with the wood framing and starting a fire. Today, knob and tube wiring is considered a fire hazard because it is not a grounded system, and is more susceptible to damage from aging and faulty renovations.

Aluminum Wiring: 1960s through 1970s

As the price of copper soared in the 1960s, it became commonplace for home electrical wires to be made using aluminum instead of copper. It is estimated that nearly two million homes were wired with aluminum between 1962 and 1972.

Many receptacles and switches manufactured during this time were not intended for use with aluminum wire. This inadequate equipment, combined with poor installation practices, resulted in loose electrical connections, which pose a potential fire hazard.

The best way to determine whether a home has aluminum wiring is to hire a licensed, qualified electrician, but it may also be possible to identify an aluminum-wired system by checking the cables that run through the basement or attic to see if the cable is labeled “AL” or Aluminum.

If your home has aluminum wiring that was installed in the 1960s or 70s, have a licensed, qualified electrician verify that all connections are properly made using wiring devices and other equipment that have been certified for use with aluminum wire.

Homes built today may have aluminum alloy wire used for the service entrance conductors and large appliances. Provided the connections, circuit breakers and devices are all marked with the letters “AL”, these types of installations are acceptable when installed in accordance with the National Electrical Code.

Grounded Electrical Systems: 1940s through Present

Electricity always seeks to return to its source and complete a continuous circuit. A typical circuit in your home has two conductors: hot and neutral. Electricity travels from the service panel to home appliances through the hot conductor, and returns the current to the main service panel through the neutral conductor. A third or “grounding” wire is also connected to all outlets and metal boxes in your home.

This critical safety feature is designed to greatly reduce your chance of shock or electrocution should a short circuit occur. Grounding wires are connected directly to the earth through a metal grounding rod or a cold water pipe. Should a short circuit or an overload occur, any extra electricity will find its way along the grounding wire to the earth.

 






 

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