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Electrical wiring

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You won’t see any «Knob and Tube» wiring in newer homes, but if your home was built in 1950 or before, take a look in the basement.

If you notice wires going through porcelain cylinders or “tubes” inserted into holes in wood floor joists, you have knob and tube wiring. You will also see porcelain “buttons” that hold the wires in place and prevent them from touching the wood the wires run along. The wires are usually insulated with a rubberized fabric cloth.

One of the main differences between modern wiring and the old button and tube is that there is no ground wire. Therefore, this type of wiring cannot accommodate electrical devices with three-prong plugs, and the risk of shock and fire is much greater.

Two Pin Plugs

Also, the black and white wires run separately, while in more modern wiring you will find that the black wire, the white wire, as well as the ground wire are all encased in a single cable. Another difference is the insulation of the wires. Modern wiring is insulated with plastic, while the knob and tube use rubber. Breakage of insulation over time on knob and tube wiring is often the reason it is replaced. It is important to note that this is often the result of overheating or mechanical abuse.

Any of the problems listed below can cause short circuits or overheating.

  • Insulation on the wiring: If there is not enough air space for the heat to dissipate, because the wiring has been covered with insulation, a very dangerous situation is created.
  • Excessive Use: Wiring for knob and tubes were installed when there were very few electrical devices in the average home. These days, with televisions, audio systems, computers, washers and dryers, the system can easily overheat.
  • Modifications: Most problems arise due to improper modifications and a lot of makeshift repairs made by DIY enthusiasts. Often times, “Knob and Tube” wiring is dangerously joined with modern wiring, as opposed to certified electricians.
  • Damage: Serious problems can arise when this type of wiring is damaged, either from wear and tear, DIY repairs, or other types of damage. Porcelain knobs and tubing can crack and wires tend to sag and fray over time, exposing live wires.
  • Fragile Insulation: Rubberized fabric insulation on k & t wiring becomes brittle over time and may chip.

Finally, in places where there is a risk of contact with water, for example the bathroom or the kitchen, this type of ungrounded system can be extremely dangerous. If so, chances are you will have a problem when you start shopping for home insurance. To avoid these problems, you may need to replace the wiring in your home.

If in doubt, have an electrical inspection performed by a licensed and competent electrician.
Source : www.squareone.ca


Three-pin plugs—aluminum wiring

While properly maintained aluminum wiring is acceptable, it will generally fail faster than copper. Insurance companies are also reluctant to insure a building that contains it because of the risk of fire.

Utility companies have used aluminum wiring in power systems since the late 1800s. It has cost and weight advantages over copper wire. Aluminum wiring is still the preferred material for power distribution applications today.

In North American residential construction, aluminum wire was used for wiring entire homes for a short time from the 1960s to the mid-1970s during a period of high copper prices. Electrical appliances (outlets, switches, lights, fans, etc.) at the time were not designed to take into account the particular properties of the aluminum wire used, and there were problems with the properties of the wire itself, even, making installations with aluminum wire much more susceptible to problems. If you must hire someone to do the repairs, by law it must be a licensed electrician.

Make sure to hire one familiar with aluminum wiring.

Unlike copper wiring, aluminum wiring is much more likely to cause a fire. American studies have shown that houses with an electrical installation made from aluminum cables manufactured before 1972 were 55 times more likely to have at least one electrical connection with a fire hazard.

There are several reasons for this:

  • Aluminum is a softer metal than copper, so it is more susceptible to damage during installation and is more likely to break under pressure.
  • Aluminum does not conduct electricity as well as copper. As it expands and contracts, wiring can loosen and overheat.
  • Aluminum will corrode if exposed to moisture. This process removes the aluminum, making the wire thinner and allowing it to generate more heat. Oxidation also causes the wire to expand, which can split the plastic casing.

This is why some insurers will not provide or renew insurance coverage for these homes without a full inspection of the electrical system. Check with your insurance company for their requirements. You may need to replace your installation.

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