Knob and tube house wiring was an early standardized method of electrical wiring in building, in common use in the United States from 1880 thru the 1930’s. It consists of single insulated copper conductors run within wall or ceiling cavities, passing through joist and stud drill-holes via protective porcelain insulted tubes, and supported along their length on nailed-down porcelain knob insulators. Where conductors entered a wiring device such as a lamp or switch, or were pulled into a wall, they were protected by flexible cloth insulating sleeving called “loom”. The first insulation was asphalt-saturated cotton cloth, then rubber became common. Wire splices in such installation were twisted for good mechanical strength, then soldered and wrapped with rubber insulation tape and friction tape (asphalt saturated clothe), or made inside metal junction boxes.
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 look into at basement joists or 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 joist or studs. If the knob and tube wiring is not easily visible, you can usually tell by look into at your electrical outlets and switches. We have a photo posted here for you to look at that will give you an idea.
We thank CityScoop.US and Zalman Sher for reminding us about this wonderful subject on Knob and Tube House Wiring. If you would like to learn more about Knob and Tube House Wiring please visit City Scoop.us/Berkeley California – electrical topics.
If you have any of these types of old house wiring, you need to contact Ethical Electrical for updated your house wiring.
Contact Ethical Electrical, Dominic Portesi he serves all communities of Upland, Ontairo, Claremont, Glendora, San Dimas, Alta Loma, Rancho Cucamonga, Covina, and Montclair California.