Welcome everyone to my first blog!
I plan to post a new story/topic every week from either an inspection I went on, home maintenance tips, or going over a commonly misunderstood feature in a house. So to start off my first blog, I’m going to talk about Knob and tube wiring.
Knob and Tube wiring was used in the late 1800’s in North America. It consisted of a single conductor wrapped in a rubberized cloth. These wires were suspended in many ceilings, and when they needed to pass through any building framing they used ceramic tubes to protect the wires from any contact. It became increasingly popular over the early to mid-1900’s because the cost effectiveness of installation over conduit or armored cable.
The reasons why this wiring system is often thought as being dangerous is for a multitude of reasons.
1. It’s not grounded! A grounding wire gives another path for electrical current to return safely to the ground without anyone being in danger of electrocution if the circuit was to short out. When there is no ground, you risk having your body become the systems grounding source which can cause a cardiac disturbance or even cardiac arrest!
2. The wires are OLD-In the past 100 years, these wires have been exposed to rodents, leaks, and just old age.
3. Added insulation over it-knob and tube wiring was designed to be installed in open areas where it can naturally cool. When added insulation is placed on top of the wiring it can lead to overheating which has caused many fires over the years.
4. Nonprofessional modifications- Back in the 1900’s they did have big screen TV’s, 220V dryers, or Jacuzzi’s. So as technology advanced, many people had the average handyman adjust the wiring system which caused the systems to overheat and be more prone to fires.
IN SUMMARY
Knob and tube is only dangerous if it has been subject to abuse over its life, and has not been maintained properly. It has been mentioned in the 2008 National Electric Code to no longer allow the wiring system to be covered by insulation due to the increased likelihood of overheating. Only an electrical professional can tell you about the systems safety. Also, if you are considering purchasing a home that was built in the early 1900’s make sure to choose a home inspector who understands Knob and tube wiring.
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