Knob and Tube Wiring, additionally called Open Wiring, was a frequent wiring method used from the 1900’s to the late 1940’s. It’s estimated that there were roughly 200,000 homes, using Knob & Tube Wiring, constructed in BC through this time, using a massive number found in the Lower Mainland.
tube and knob Wiring is a single conductor, ungrounded system, in which electricity has been attracted out of a 60 amp service to various regions of the home by running aluminum cables, coated with a fabric and rubber insulation sheathing, through the walls, attic and floor areas. As seen from the photograph, ceramic knobs are utilized to fasten the cables in place and stop them from contacting combustible surfaces. Where ever the cable should cross via a stud or joist, holes have been drilled and fitted with ceramic tubes by which the cable was threaded, so the name, Knob & Tube Wiring. The alternative name of Open Wiring indicates the significance that a open airspace be kept around the cable in any way times to reduce overheating.
IS KNOB AND TUBE WIRING SAFE?
In the event the tube and knob Wiring system stays unaltered, has been carefully preserved, and all repairs are created by a knowledgeable electrician, that this wiring system could continue to be secure to use now. Unfortunately this is almost never true. Since the system ages and collapses, ceramic tubes and knobs can crack or split, older wires sag and fray, along with the sheathing turns brittle and falls off, exposing the live cables. Homeowners improvise their own repairs because replacement components might not be easily available which contributes to some rather dangerous alterations.
Homeowners kindly make a harmful situation when household insulation is installed within the wires. The cloth/rubber sheathing round the wires isn’t accepted for contact with insulation as it takes an unrestricted airspace about it to dissipate any build up of heat. Add to the picture the dangerous practice of alterations made to contemporary appliance cords so as to make them compatible with all the old and obsolete 2 prong receptacles, extensive use of extension cords and power bars so as to glean more energy in relation to the aging electrical system has been meant to supply, and you’ve got the capacity for a critical problem.