Is Knob and Tube Wiring Dangerous?

Submitted By
mdreesen
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Electric
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Q:

I have had knob and tube since 1927 but have had the main box and some wiring updated.  Does that help to minimize danger to my family?  It is very expensive to have it all wiring repalced at once.

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Answers

To some extent, yes, but knob and tube is dangerous for a number of reasons. 

First, it is an ungrounded system.  And second, it is designed to be “air cooled.”  The reason that knob and tub wiring consists of wiring strung between knobs and run loosely through tubes is so that air can circulate around it and cool the wiring.  This was safer in 1927 when we had very little insulation in attics.  Now though, we pile insulation in for all the right reasons and as a result, knob and tube wiring becomes buried and can more easily overheat. 

If I had to choose one area to make sure knob and tube was replaced, it’d be the attic and any other area where old wiring runs though insulation.

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