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Since electrical wires get hot due to the resistance of the electrons flowing through the wire, a knob and tube system requires adequate clearance around it-good ventilation-in order to dissipate the heat that is inherent in electrical wiring, so it is not designed to be covered with any material such as the modern insulation that we put in our attics. This often happens when we have insulation added to the attics in older homes or when the attic or foundation crawl space is used for storage. Older wiring was specifically installed in open spaces so that it would stay cool. The insulation on the wires is rubber or cloth that melts or burns at a relatively low temperature, so if the wires are covered by insulation other than the wire insulation itself, the wires could heat up enough to burn. Unfortunately, since a knob and tube wiring indicates an older system, the insulation on the wires probably is brittle and might even be missing or damaged in some areas, especially if wildlife have intruded into the attic or foundation crawl spaces where most knob and tube wiring is located. Additionally, the insulation installers themselves typically are not familiar with the design of older electrical systems.
Many modern appliances have a three-prong plug, and modern electric outlets have three slots: a short vertical one that indicates the hot wire, a tall vertical one that indicates the neutral wire, and a round one that indicates the ground wire. A ground wire is necessary if you are plugging in appliances that have three prongs in the cord's plug. The three-to-two prong adaptors that are sold at grocery stores and home improvement stores bypass the ground safety circuit and should not be used under any circumstances, particularly for computers and |
plasma televisions. Without a ground, you're putting yourself and your equipment at risk.
 
Knob and tube wiring with porcelain tubes and a modern electric outlet showing slots for hot (yellow), neutral (blue), and ground (red) wires. Years of experience and, unfortunately, property damage, personal injury, and even deaths have resulted in increased knowledge about electrical systems, knowledge that indicates that a three-wire system with a ground wire currently is the safest. Recommend further evaluation by licensed electrician before close of escrow. Recommend contacting preferred insurance company before close of escrow to ensure that appropriate homeowner's insurance can be obtained on the structure if active knob and tube wiring is present. |
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