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Question DetailsAsked on 11/5/2013

Is knob and tube wiring safe

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3 Answers


Short answer: NO, you should have it removed.

Answered 6 years ago by Steve0512


You should have it removed and upgraded to current code in your area. Knob & tube was used before todays shielded and unshielded lower gauge wire and canoot handle the electrical loads of today. It is a 2 wire system with no safety ground as required by current electrical code. Too much of a load and the wire can potentally get hot and you cannot place any insulation over the wire. A potential fire and safety hazzard.

Answered 6 years ago by hosey


The other answers may have assumed you know what knob and tube wiring really is. In caee you do not, modern wiring is aluminum (generally only for main feed to fuse or breaker panel) or copper wires which have the "live" wire(s), a neutral or return wire, and a ground wire in a plastic insulation sheathing, or enclosed in a metal flexible sheathing or conduit for exposed locations.

Knob and Tube wiring used exposed bare wire, almost always without a ground and sometimes without a neutral return wire (using instead a common neutral than ran throughout the house, or even sometimes the rebar in the foundation as the return or neutral conductor). Because it is bare wire, any contact with anything at all conductive can cause a short and possible fire - so it was installed on "knobs" (glass or bakelite insulators similar in design to those used on bare wire on power poles today) and "tubes" (glass, ceramic, or bakelite insulator tubes) that the wire ran through when it had to penetrate a wall, ceiling, or framing member. Basically it can short out and potentially cause a fire for a number of reasons - moist insulation, rodent contact, cracking of knob or tube, breaking of a wire, melting due to overload, etc. In addition, the wire size was based on much smaller elecrical loads than modern houses use - 5-20 amp circuits were common, whereas most circuits today are 15-30 amp. Because the wires are bare, the risk of accidental electrocution is also quite high - so it just is not something most people would ever consider having in their house.

You can find some info on likely costs for replacement in a few answer links right below these answersw, and others about whole-house wiring and panel replacement in the Home > Electrical link. It is a significant cost - at least three or four thousand $ to as much as $10,000 in a normal sized house to replace the household wiring and to replace the fuse panel with a circuit breaker panel.

Answered 6 years ago by LCD

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