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Knob and Tube Wiring

What is Knob and Tube Wiring?

If your house was built before WWII and hasn’t been updated or renovated, you probably have knob and tube wiring. What is Knob and Tube Wiring? It’s an old type of electrical wiring that consists of two separate wires, one hot and one neutral, that are suspended by ceramic knobs and run through ceramic tubes to protect them where they pass through walls or ceilings.

knob and tube wiring

While this type of electrical wiring was once considered an innovative technology, it is now considered outdated and unsafe due to its potential to cause electrical fires and its inability to handle modern electrical loads. Modern house wiring has three to five conductors encased in a tough thermoplastic jacket.

Why is Knob and Tube Wiring Dangerous?

Is knob and tube wiring safe? The answer is no.

Knob and tube wiring is a single conductor system, the copper is protected by a rubber, fibre type coating which after 50 years or so has begun to break down. Possibly having bare copper exposed. The most dangerous part of this type of wiring is when it has been “tapped into” by a “handyman”.

We have seen connections where the original knob and tube insulation have been stripped off and new wiring has been laid beside or twisted around it and then taped in place. This is an electrical fire waiting to happen.

what is knob and tube wiring

Another common problem is replacing the original fuse with a larger size fuse. Someone is making toast and boiling water in the electric kettle at the same time and the fuse blows, I know, let’s put in a bigger fuse! This solves the problem of the fuse blowing but causes a much more dangerous problem. A copper wire which was designed to safely carry 15 amps of electricity is now carrying 20, 25, or even 30 amps. The wire heats up, which causes the protective insulation around the wire to break down.

I have seen knob and tube wiring where one small bend of the wire will cause all the original insulation to fall off. The copper itself is brittle and prone to breakage.

If the knob and tube wiring is in good condition and has not been tampered with, there is a way to make it safe. See solution 2.

Knob and tube wiring also have no bond (sometimes incorrectly referred to as ground) wire, the bare copper wire you see in modern wiring. If the “hot” (black) knob and tube wire touch a copper water line, or any other metal plumbing line and the wire’s insulation has broken down the metal may become electrified and the fuse or circuit breaker will NOT trip.

There are solutions to make knob and tube wiring safe.

1) The best solution is to remove it and install modern Loomex, Romex NMD-type wiring.

2)You can also GFI protect it. This means installing a GFI receptacle or a GFCI breaker as the first device the electricity flows through. Then everything “downstream” is protected. This must be done for each circuit. Your wiring is safe and will be accepted by your insurer.

Replacing Knob and Tube Wiring

cost to replace knob and tube wiring

If your home still has this outdated type of electrical wiring, it is important to upgrade to a modern electrical system as soon as possible. Not only is knob and tube wiring a potential fire hazard, but it can also reduce the value of your home and make it more difficult to sell.

Upgrading from knob and tube wiring typically involves replacing the existing wiring with a new electrical system that meets modern safety standards. This process can be complicated and expensive, as it often requires opening up walls and ceilings to access the existing wiring and installing new electrical components throughout the home.

How much is the cost to replace knob and tube wiring?

The cost to replace knob and tube wiring in Canada can vary significantly depending on a number of factors, including the size of your home, the complexity of the electrical system, and the cost of labor in your area. The average cost to replace knob and tube wiring in Canada ranges from $8,000 to $15,000. However, this cost can increase significantly if your home has unique electrical needs, such as a large number of outlets or high-powered appliances.

If you have knob and tube wiring and are concerned about it or would like a free estimate contact us today!

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