Knob and Tube Wiring
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Knob and Tube Wiring What is it?
Knob & tube wiring is a type of wiring which was in common use until the 1940’s and sometimes used as late as the 1950’s. The nick-name is derived from the ceramic knobs that are employed to insulate and secure the wiring runs and the ceramic tubes employed to protect the wires where they pass thru potentially abrasive materials (primarily wood joists, studs etc.) Unlike subsequent wiring systems where all the wires in a run are enclosed in a cable, the two wires (black/hot and white/neutral) run separately and only come together at a terminal (switch, receptacle, fixture, junction box etc.).
Knob & tube wiring does not provide a third wire for grounding and is therefore considered unsafe by current standards, in kitchens, bathrooms, laundry rooms and outdoors. In other areas, knob & 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.
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 tendency to overheat when insulation is packed around it. Also since it has been around for some time now the chance of it having been overheated due to over fusing is much higher. This has become an issue with insurance companies as they no longer want to insure houses with more than one circuit of knob and tube.
If your house does have knob & tube wiring it should be removed by a licensed electrician. We can remove existing insulation to give the electrician a clean work situation. And then your new insulation would be given a fresh start.
Insta-Insulation reserves the right to cancel without penalty in the event of an unsafe situation.