There are existing homes that have the knob and tube wiring which was the standard system used in North America several decades ago. The question here is whether knob and tube wiring is unsafe and dangerous, and whether it should be replaced during an electrical maintenance retrofit. The ancient wiring system is considered obsolete and a fire risk but some of the fears are unfounded. Knob and tube wiring only becomes hazardous when it has been subjected to improper modifications and when insulation has been wrapped around the wiring.
What is knob and tube wiring?
Many people are no longer aware of knob and tube wiring because they were born in the age of the modern wiring system. Knob and tube wiring includes insulated copper conductors passing through the building lumber frame with a ceramic tube used to insulate wire from wood. The ceramic knobs are considered good insulators as long as they are not damaged or modified. Damages to the system are usually the result of age, exposure to leaks and rodents that have chewed on the wires. Contrary to what many people think, knob and tube wiring has its advantages. The K & T wiring system has higher ampere capacity than wiring system of the same gauge. Why is this so? Because the hot and neutral wires are separated by around 4 to 6 inches that allow them to easily dissipate heat into the air. Installation, retrofitting, and electrical maintenance of knob and tube wiring requires great skill.
Problems associated with K & T wiring
Knob and tube wiring is not actually illegal and there are states that do not require an immediate electrical maintenance to modern wiring system; however, insurance companies consider K & T wiring hazardous enough to disapprove your coverage. Most knob and tube wiring have been modified and many safety hazards are associated with improper modifications particularly those done by unskilled electrical maintenance workers. When building insulation is wrapped around the wires, it becomes a fire hazard. The lack of a grounding wire increases the possibility of electrical fires or damage to electrical equipment. Knob and tube wiring is so old that it has obviously depreciated. When the K & T wiring was introduced in North America, there were no computers and electronic devices. There were no convection ovens and high end TV and sound systems. The electrical requirements of modern day appliances can no longer be handled by the traditional wiring system and attempts at further modification will only make it unsafe.
If you are planning to buy an old home, a good option is to have the wiring system checked by a licensed electrician. Only a professional can confirm whether the old house has knob and tube wiring. Replacing the wiring system with modern Romex cables requires a big investment and the job can take weeks to be completed. Request for an estimate of the costs involved in rewiring so that you can make a deal with the seller. Old homes can be attractive and investment-worthy but not when they are electrically unsafe.