The electric wiring most commonly installed in the homes which were constructed from the 60 year period between 1880 and 1940 is called “knob-and-tube.” The cables which ran parallel to floor joists were sandwiched between two ceramic discs (a “knob”); cables which were threaded through floor joists were sheathed in a ceramic tube (a “tube”). Even though it required skilled labour to set up, knob and tube has been widely used because of its relatively low price compared to its choice: conduit, armoured cable and junction boxes. Lots of Toronto’s older homes are still working with knob and tube wiring.
When it was first introduced, tube and knob proved to be a secure and economic means to cable Toronto homes. Through the years, three problem areas came into light:
1) Deterioration of that elastic cloth insulation on the cable itself (“loom”).
2) DIY homeowner repairs. Its availability tempted homeowners to perform their own repairs as opposed to calling in an electrician.
3) An ever expanding number of power-hungry appliances that these initial wiring technologies didn’t consider.
If your home has tube and knob, then your pipes is at least 70 years old. The soldering and splicing in the joins might have slowed with age. The loom about the cables might be worn departing wires vulnerable. Damage might also have been due to rodents or from renovation action.
Because tube and knob does not end at a closed intersection box, it’s very prone to amateur repairs. Many homeowners “solved” the problem of overtaxed circuits which blow fuses by substituting 15 amp fuses with ones of 25 or 30 amps. This “fix” causes wires to overheat and insulation to become brittle or burnoff. The other DIY fix is that the patching of additional sockets to the current system. Owners are known to secure their own handiwork with masking tape, scotch tape and Band-Aids!