WIRING TYPECONCERNS
To 1950's
“Knob and tube”  (K&T) wiring
• Two separate conductors held in place by ceramic knobs. 
  • No ground protection.
  • 2-prong receptacles swapped for modern 3-prong, giving false impression of ground protection.
  • Limited number of receptacles for today’s demand. 
  • Dangerous “handyman add-on” circuits, poor connections can be most dangerous, resulting in jot-spots at the added connections.
  • Insulation deterioration due to overloading of circuits and over heating of conductors. Overfusing combined with overloading the circuits significantly raises the temperature of the conductor beyond their designed temperature limits, resulting in a fire hazard. NEVER increase the fuse/breaker size
1950-1962

Ungrounded twin-conductor cable, called “NMD-1”
• New method of wiring introduced. Contained the two conductors in one jacket.

• NMD-1 contained no ground wire (Ground wire was not required in code until 1962).
• Replaced K& T wiring, due to ease of installation



  • Had the same concerns as that of knob-tube: No ground protection. Grounded receptacles were not required until 1962.
  • 2-prong receptacles swapped for modern 3-prong, giving false impression of ground protection.
  • Limited number of receptacles
  • Insulation deterioration
  • Often incorrectly identified as “modern grounded cable”.Temperature rating of this cable is 60°C
1962-1984
NMD 3 & 6
• The predominant cables used during this period.
• The insulation temperature ratings of these cables are 60°C and 75°C respectively.
• Worked fine for most circuits, but not for recessed ceiling lighting (pot lights). 
  • Fires from Recessed Lighting​.  In the 1970s and 1980s recessed lighting became popular. However a number of fires resulted from these fixtures due to inability of conductors to handle the heat.
  • Since 1984 Electrical Code requires that all ceiling fixtures be wired with a cable rated at 90°C.
  • Cables rated at 60°C and 75°C are not suitable for modern fixtures.
1965-1974
Aluminum wiring (Al)
• Installed in the vast majority of houses as an inexpensive
solution to escalated price of copper.
• Can be extremely dangerous if not checked and maintained regularly by a licensed electrical contractor.
• Homes wired with Al, are 55 times more likely to lead to structure fires than copper wired homes. 
  • Connections become loose over time, leading to fire.  This results in very hazardous conditions, which often lead to fire.  Concerns are not the cable, but the aluminum-copper connections.
  • Mechanical process: Due to the unequal expansion and contraction rate of two different metals.
  • Chemical process: “Oxidation”, Aluminum oxide, is an insulator, and is formed at the connection. This further decreases the quality of the connection, creating additional heat.
  • Using non CO/ALR devices, Modern Decora style devices needs proper Copper pigtail.  Increases electrical resistance, resulting in overheating that can lead to a fire.
  • Not using Aluminum-Aluminum, or Copper-Aluminum connectors with anti-oxidant compound.
1984-PRESENT
Modern cable (NMD 7 & NMD-90)
• Modern house wire. Jacket of PVC.
• Approved for use with ceiling fixtures.  Rated at 90°C. 

  • Inappropriate application. Home should be checked to confirm that it has not been installed in incorrect locations or manner.
  • Designed for use indoor dry locations, and away from the weather.  Not for outdoor locations.
  • Not for underground or wet locations. 


​​​​Wiring Safety


The Canadian Electrical Code, CE code is a standard published by the Canadian Standards Association pertaining to the installation and maintenance of electrical equipment in Canada.

The first edition of the Canadian Electrical Code was published in 1927. The current (23rd) edition was published in 2015. Code revisions are now scheduled on a three-year cycle.The Canadian Electrical Code serves as the basis for wiring regulations across Canada. Generally, legislation adopts the code by reference, usually with a schedule of changes that amend the code for local conditions.

Residential Wiring and Associated Risks


​Since the introduction of electricity in homes, circa. 1910, various electrical wiring types have evolved. The primary types can be loosely grouped into five different categories. All wiring types if installed and maintained correctly can be safe. However, if not installed or maintained correctly, each has potential risks.