Since January 2003, the Electrical Safety Authority (ESA) has received an increasing number of questions about the safety of knob and tube wiring. In particular, purchasers or owners of older homes are finding that many insurers will not provide or renew coverage on such properties. In some cases, the insurance companies are requiring a total replacement of this wiring prior to providing insurance coverage.
Knob and tube wiring, more recently referred to as open wiring, was a wiring method used in the early 1900s to 1940s in the residential sector. Over the years wiring installation practices have changed in the residential sector and knob and tube wiring is no longer installed.
“Knob & tube” conductors should be replaced where exposed conductors show evidence of mechanical abuse and/ or deterioration, poor connections, overheating, or alterations that result in overloading, or if changes to the wiring contravene any section of the Ontario Electrical Safety Code (OESC).
- Homes with knob and tube wiring may not have the electrical capacity to meet today’s needs. As a result, homeowners have modified their electrical system with what ESA classifies as unsafe practices:
- Improper use of extension cords – using improperly rated extension cords, or using extension cords as
permanent wiring; - Improper fuse replacement – using 20 or 30 A fuses to replace 15A;
- Improper connections – adding receptacles and outlets on existing circuits or improperly connecting to the knob and tube wiring (this work should be done by a licensed electrician);
- Removing ground pins – ground pins on power bars or electrical equipment should not be removed to
accommodate the two pin receptacles used in knob and tube wiring (2 pin to 3 pin are not permitted) - Improper replacement of two pin receptacles. If you require a three prong receptacle, only use a ground
fault circuit interrupter (GFCI) receptacle.
