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Knob and Tube Wiring

Many houses constructed pre 1950's have what is called knob and tube wiring. One can determine if you have this type of wiring in your home, by closely looking at basement or attic and looking up at the joist or down under the insulation in the attic rafters
To determine if your home is wired " knob and tube", look for ceramic knobs or tubes in which the wire gets attached to, or passes through, joists or studs. If the knob and tube wiring is not easily visible, you can usually tell by looking at your electrical outlets and switches. You may only have two prong outlets to plug into. Basically, no ground at each outlet or fixture outlet means knob and tube wiring is present, likewise if you have older pushbutton switches, this is also a good sign you may have knob and tube

Nowadays, Home owners with knob and tube wiring may find it difficult or impossible to obtain insurance on their home because most insurance companies are reluctant to insure a house they perceive as risky. Insurance companies usually require a certificate of inspection and compliance from a licensed electrician, that all knob and tube has been removed and replaced with modern 3 wire grounded circuits before it will insure a home that previously had knob and tube wiring. After the electrician rewires your home, they give you a satisfactory assessment of your home, and the insurance company will consider giving an insurance policy for your house.
 
Knob and tube wiring does not provide a third wire for grounding and is therefore considered unsafe in kitchens, bathrooms, laundry rooms and outdoors. In other areas, knob and tube wiring that is in good condition with sheathing intact, properly protected from damage, and that hasn't been subjected to extended periods of overloading which can cause it to become brittle, should not pose an increased safety risk.
 
Aside from the preceding concerns, the primary risk with knob and tube wiring, it seems, is its relative accessibility for amateur repairs, upgrades and maintenance. It is not uncommon to see a system with knob and tube wiring that has a history of amateur work. If a house does have knob and tube wiring it should be inspected to ensure that it is properly installed and in good condition.
If a few, but not all, of the circuits are in poor condition they can be replaced eventually without rewiring the whole house. However, if most or all of the circuits are in poor condition, it may be more economical to completely rewire the home. At Hi Amp Electric, our professional Pierce,Thurston,Mason,Lewis,and King County electricians can rewire your old, unsafe knob and tube wiring and replace it with modern electrical circuits.
 
 

What are some concerns with Knob and Tube wiring?

Below is a picture of knob and tube wiring which has been a safety concern because of its tendancy to overheat when insulation is packed around it. Also since it have been around for some time now the chance of it having been overheated due to overfusing is much higher. This have become a issue with insurance companies as they no longer want to insure houses with more than one circuit of knob and tube. There may still be a couple insurance companies that will insure knob and tube wiring and if you know of which please let us know.

When can your expect to see knob and tube wiring in a house. It was installed in homes up to the 1950's and you will likely see it in homes built before there was wiring installed initially.

 

 

 

 

 

 

 

 

Knob and tube wiring was sometimes installed with a fuse on both the neutral and the power wires. This is a concern because in the event that the fuse on the neutral is blown the home owner will think that the circuit is no longer live when in reality you can still be hurt by injured because the circuit will still be live.

Because the uses of electricity has changed so much in the past 60 years since it was last installed it is common to find circuits that were extended by home owners who may or may not have done a good job. Because knob and tube was installed without junction boxes people think they can still make connections without junction boxes when in fact this is not any longer allowed. Lastly since the wiring is typically quite old the chances of it having been damaged is higher and it has aged, meaning the sheathing may be brittle or broken.

 
 

 

Did you know that most of the Home Owners Insurance Companies will not insure a home if it has Knob and Tube wiring? If you are looking at a home and are wondering how to determine if it has Knob and Tube wiring a good place to start looking is in the basement or the attic. Here is an example. If you look closely the porcelain knobs are in the back ground and If you look closer you can see the wires passing through a porcelain tube in the wall. The largest problems with Knob and Tube wiring is: 1. The sheathing gets damaged with age. 2. Improperly tapping into the system with newer methods of wiring. 3. Improperly protecting the circuits in the panel.




There are a few insurance companies that will insure a home if a Licensed Master Electrician will write a letter stating that all of the Knob and Tube wiring is safe. You should ask your insurance company before settling on a home.
If you need help in identifying this issue give us a call at 1-888-278-3616.