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Knob & Tube Wiring: What You Need to Know

knob and tube wiring St Paul

About Knob & Tube Wiring

Knob and tube wiring was one of the first electrical wirings in homes. It’s inexpensive compared to other options at the time, but we have moved away from this type of electrical wiring since then. Today, there is a strong aversion to this traditional house wiring, particularly knob and tube wiring. Some of that dread is reasonable, and some of it, like any fear, stems from a lack of knowledge. In this article, we discuss everything you need to know about knob and tube wiring

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What Exactly is Knob & Tube Wiring?

Knob and tube wiring is simple copper wires in a rubber wrapping. The term’s tube component came from porcelain tubes drilled into structures to carry wires. So the wire could pass through the framing without touching it. As a result, the house did not sink or move due to seasonal weather variations, preventing wires from being crushed or rubbed off.

The entire system was built to fulfill the time’s building and electrical requirements. The cables generated a lot of heat as an electric current passed through them. Because of the heat, the porcelain knobs kept them away from the framing. As a result, they were protected from the heat. Largely to meet the demands of the time, most installations were built to securely support 10-amp loads per circuit. Furthermore, this method resulted in physically and electrically strong joints when properly done.

knob and tube wiring St Paul

The Benefits of Knob and Tube Wiring

Yes, believe it or not, knob and tube wiring had some notable advantages over its predecessors!

Low Price

Knob and tube were far less expensive to install than its competitors, which were two and three times the price. Initially, the materials, rather than the electrician’s salaries, were the most expensive element of the equation in the electrical industry. Labor costs for electricians increased substantially quicker than material costs for electrical components as electrical systems became more complex and electricians became more trained.

Additionally, knob and tube wiring is very labor-intensive to install, hence this shift in labor vs. materials caused knob and tube installation prices to surpass competitors and was one of the primary reasons for its decrease in popularity.


The use of porcelain insulators was another advantage of knob and tube wiring. Porcelain is incredibly durable and has a nearly infinite lifespan, giving superb protection with little to no expiration date, which is difficult to find. Also, the porcelain knobs did a good job of keeping the cables from becoming too tight during installation.

The Drawbacks of Knob and Tube Wiring

So. you knew I’d get to it eventually, didn’t you? What about the doom and gloom? Yes, there are some drawbacks to knob and tube wiring as well.

There is No Foundation

That’s accurate, a knob and tube arrangement does not include a ground wire. There were only two wires included: a hot and a neutral. It wasn’t until the 1960s that a dedicated ground wire was incorporated in every circuit on a consistent basis. So, if there are any power surges or overloaded circuits, the ground is critical. If everything works flawlessly, you don’t need the ground wire, but when is everything perfect?


When there is air to breathe, the knob and tube operate well. When it is covered with blown-in insulation, it is unable to cool down and release heat as planned, increasing the risk of fire. This problem can be caused by anything packed around the wires that prevents air passage, not simply insulation. Even the present building code prohibits installing insulation on top of active knob and tube.

Sheathing That has Been Worn

Unlike porcelain insulators, natural rubber or asphalt-soaked cotton sheathing dries out and breaks down with time, exposing the wires and increasing the risk of electrical shocks and fire. During renovations, old brittle sheathing is easily torn or damaged, adding to the danger.

Increased Power Requirements

This, in my opinion, is the most serious problem with knob and tube wiring. A house in 1918’s electricity needs is dwarfed by a residence in 2018. In the first half of the twentieth century, electricity was primarily used for illumination, with only a few appliances being used. With central air conditioning, computers, TVs, internet, washers, dryers, refrigerators, and other contemporary conveniences, our homes have become massive energy consumers, and outmoded electrical systems are struggling to keep up.

In the 1920s, a typical house had a 60-amp main service panel (the total electrical service capability the home can handle). Nowadays, the primary service panel is normally at least 150 amps, with most larger houses requiring 200 amps. Knob and tube wiring was never designed to carry loads of that magnitude.

Incorrect Modifications

Another major concern is faulty craftsmanship in the course of the alterations. Improper splices are only one aspect of the problem. Overloaded circuits, such as the one we just discussed, are common when the home’s power needs grow marginally. For example, a 10-amp knob and tube circuit may have been slightly overworked, so the homeowner replaces it with a larger 15-amp fuse to prevent it from blowing so frequently. Years later, as new appliances are installed, the same circuit is accidentally overloaded, even more, making it much more deadly.

Necessary to Replace the Knob & Tube Wiring?

Now that you’ve learned about the benefits and drawbacks of knob and tube wiring, what should you do? In almost all cases, knob and tube wiring need an electrical upgrade, if you ask any Minessota electrician. Other than saving money, knob and tube give very little advantage today, and when weighed against the potential dangers, it simply does not add up.

Does this imply that you must demolish your walls in order to replace them? Certainly not! The knob and tube do not need to be removed from your walls; they only need to be detached so that they are no longer functioning. A good electrician in St. Paul can rewire an ancient property without tearing down entire walls, instead of cutting small tactical holes to fish their new wires into position. Don’t spend the money to completely remove every trace of knob and tube. Instead, ensure that every circuit is completely unplugged and rewired using modern wiring.

When your home has modern wiring, you will sleep better and ultimately earn better insurance rates. In most cases, the insurance savings will pay for the rewire in less than ten years. Rewiring is a no-brainer when you consider the reduced risk of fire or other electrical problems. Contact McQuillan bros for our electrical services or knob and tube wiring replacement in St. Paul.


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