How Old Is the Wiring in Your Home?

If the light switches and outlets work, we don’t always give them a second thought. But the wires that power them vary greatly in their load capacity and safety. The biggest factor to consider when checking the safety and efficiency of your electrical system is the age of those wires. If the wiring is old enough, the protective insulation could have deteriorated, may not be properly grounded, or may not provide your home with sufficient power for modern electrical demands.

A Little History
Before we take a look at the various types of wiring you may find in your home, let’s go back to the beginning before electricity was a standard element of home construction. It was the experiments of scientists like Benjamin Franklin that proved lightning was a form of electricity in the mid-1700s. Not only was it proven, but it ushered in a power-driven new era. And Franklin then focused his attention on how to protect people and buildings from the dangers of electrical storms.

Lightning Rods
Franklin is credited with inventing the lightening rod, which is still an important way of diverting dangerous electrical charges from our homes. According to a report by State Farm in 2021, Georgia ranks #2 in insurance claims for lighting strike damage. While lightning rods may not be standard, especially in urban areas like ours, they are worth consideration.

Despite the danger of lightning strikes, the wires running through your walls and between the joists in your ceiling can be just as dangerous if not updated and maintained. We keep this tri-fold display in our office to help educate customers about how wiring has changed over the years. Please note that dates are approximate.

Wiring Through the Years

  • Knob-And-Tube Wiring: 1890 – 1930s
    – This wiring uses rubberized cloth insulation which eventually dries out, cracks, and falls off.
    – Hot and neutral wires run separately.
    – Don’t panic if you see it in your home. Have an electrician check to see if it was just left in place when the house was rewired.
  • Cloth Sheathed Cable (Rag Wire / Early Romex): 1920s to 1950s
    – This non-metal rubberized cloth sheathing became popular because it could be installed more quickly.
    – The cloth insulation deteriorates and becomes brittle with age.
    – Hot and neutral wires were run together.
    – There was no separate ground wire initially, but it was added later.
  • Flexible Armored Cable (AC): 1930s to 1950s
    – The flexible metal protects the wires better than the previously used rubberized cloth.
    – When properly installed, the metal is a source of grounding.
    – There is no separate ground wire, so if the metal pathway is interrupted or incomplete, it could be dangerous.
  • Non-metallic Cable (PVC): 1950s to 1970s
    – Synthetic rayon or vinyl jackets were used during this period but were eventually replaced by PVC.
    – PVC does not get brittle or crack like older rubberized materials.
    – Also during this period, a grounding conductor was eventually added.
  • Modern Romex: 1970s to Today
    – Each conductor is insulated, and the entire bundle is contained within a color-coded PVC jacket.
    – It’s flexible, heat-resistant, fire-resistant, and easy to install.
    – Copper wire conductors are used.

Wire Insulation
One of the primary differences in these wires is how they are insulated. Over the years, we have moved from rubberized cloth, to metal, and finally to vinyl and PVC.

*Asbestos was also commonly used to wrap and insulate wires before the 1980s. While its existence in your home’s wiring may not pose an everyday health risk, it should be noted for anyone thinking about doing a DIY project that could disturb wires and potentially release asbestos into the air. It could even be present on the inside of an older electrical box.

Copper is known to be the best conductor of electrical current. Older wiring installations could use aluminum or copper-clad aluminum, but it is no longer used in construction. It becomes defective quicker and does not provide sufficient conductivity for all applications. It is safe, but only for receptacles and devices rated for use with aluminum.

Ground Wire
Another difference in wiring over the years has been how it was grounded…or not. Some relied on metal housing, but its ability to do the job depends on proper installation.

No matter what type of wiring you’ve got in your home, it’s critical to keep it updated and maintained. Modern safety features such as ground-fault circuit interrupters (GFCIs) and arc-fault circuit interrupters (AFCIs) help protect against electrical fires and shock. They sense the current flow and can shut the power off before major damage or injury occurs.

Learn More About Preventing Fires With AFCIs

Need someone to evaluate a possibly outdated electrical system? Don’t hesitate to contact the experts at Bray.

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