When insurance companies shifted their principles for old wiring, home buyers were left having a demand for more information regarding exactly what they have been buying. “Knob and tube” refers to an un-grounded wiring system employed for lighting and power in buildings from approximately 1880 to the 1930’s. The name describes the two ceramic insulating apparatus utilized in the wiring; the “knob” and also the “tube.”
The knob has been used to keep the open conductor away from the surrounding material. The knob has been also utilized while the conductor required turning into a corner, as shown here. The tube was utilized to isolate the cable as it passed through surrounding material.
Many homes in the Metro-Boston area are well over 100 years old and were wired using all the knob and tube electric system. Through renovations, contractor softens come across knob and tube wiring inside walls and ceilings. Though not necessarily illegal, the elderly system might not be safe.
National Electrical Code (NEC) Article 394.12-5
National Electrical Code (NEC) article 394.12-5 does not permit thermal insulation to be inserted to wall or joist cavities which have knob and tube wiring, because the insulating material increases the danger of the wiring corrosion and resulting in a fire. Unfortunately many homeowners are unaware that they have knob and tube wiring inside their walls, and add insulation to decrease their home heating and cooling outlays, exposing themselves to the possibility of fires in the overheating conductors. Therefore, now it’s typical for insurance companies to need all knob and tube wiring has to be eliminated if new owners take possession.
For more information on knob and tube wiring, or in case you want to assess whether your home has it please contact us. In addition, we offer home inspections for new purchases to learn whether your new home in Boston or surrounding areas has possible security issues or code violations.