Electrical Conductor: Is Knob-and-Tube Wiring Safe?

Knob-and-tube wiring is a form of electrical conductor that was prevalent in homes during the period between 1880 and 1930. Older homes that were build in this time frame will feature this type of wiring. The wiring has since been replaced by new wiring standards. In accordance with the National Electrical Code NFPA 70, it is not permitted for use today (except in very limited and extreme situations).

Knob-and-tube wiring is not safe. In fact, older homes that still have this type of wiring in place should be rewired immediately by a qualified electrician. Rewiring will help to reduce fire dangers and other hazards that may be present.

No Safety Ground Conductor

Knob-and-tube wiring does not use a safety ground conductor that is common in newer wiring. The absence of the safety ground conductor means that power surges can blow out the wiring system and potentially cause a fire. In fact, the biggest danger that this type of wiring presents to you is fire hazard.

Placement of Knob-and-Tube Wiring

In addition to no safety ground, the wiring is typically placed in the space between the studs and drywall without regard to any insulation. Insulating the wire presents a fire hazard because knob-and-tube wiring is prone to running hot and causing any flammable material to catch fire.

Damage to Knob-and-Tube Wiring

Knob-and-tube wiring is also subject to damage from a home renovation, rodents and even carelessness when you hang a picture on the wall. All of these dangers increase the likelihood that the wiring will fail and lead to a dangerous situation such as a home fire.

Types of Homes Where Knob-and-Tube Wiring Is Found

Homes built during the 50-year period between the end of the 19th century and middle of the 20th century were commonly wired with the knob-and-tube style. As methods for electrical conductivity evolved and more emphasis was placed on safety and ground breaks, knob-and-tube wiring became less and less prevalent. The NEC addressed the problems with knob-and-tube wiring by limiting it use and prohibiting such processes as introducing blown insulation in a wall containing knob-and-tube wiring. This was done to make sure that the wiring would not be exposed to a potential fire danger.

Dealing with Knob-and-Tube Wiring

If you are not sure whether your home contains this type of wiring, you should have an electrician check out the situation in your home. If your home was built after 1930, you won't have the same concerns as a person who bought an older house.