Replacing knob and tube

topic posted Thu, July 14, 2005 - 5:02 PM by  Unsubscribed
I am helping a friend replace knob and tube. Fascinating how it was done way back then.
I have helped install much commerical electrical but hardly any residential.

Hints? Links? Tips?


posted by:
  • Re: Replacing knob and tube

    Thu, July 14, 2005 - 6:58 PM
    the cost of those fuses and such is pretty high. You could put in a sub pannel and run some romex or conduit depending on where it is and bring it up to code. It is a good idea to rplace with newer technlogy because that fabric they used to wrap the cables with get dried out and are prettty scary so far as fie safety, and the wire gets nice and coroded too.
  • Unsu...

    Re: Replacing knob and tube

    Fri, July 15, 2005 - 6:44 AM
    Replaceing knob and tube meand replacing all the attendant wiring. Just discinnect the stuff everythere - especially at the box. and re qire with Romex. You'll need new junction boxes too as the oold boxes usually won't accept romex connectors.
  • Re: Replacing knob and tube

    Wed, July 20, 2005 - 9:45 AM
    Knob and Tube is fine, it works, don't give yourself so much grief. The only three reasons to replace knob and tube is

    1. it's all cracked and creates a fire hazard

    2. you want blow in insulation

    3. you have very pricey electronics that require grounding

    other than that you don't need to worry. when you want to update anything with knob and tube, use a plastic junction box and tape around the wires where they enter the box. from there you can use romex or conduit. only use romex if it will be covered by sheet rock and you are threading in through wood studs. conduit is better in your basement and anywhere rats can gnaw through cable. BIG TIP: limit each knob and tube circuit to no more than 15 amps. back in the days voltage was 110, now it's 120 (more like 125). Don't even think of wiring knob and tube to 240 volts, you wouldn't even have enough wires.

    my house was built in 1931 in san francisco(we have the most strict code) and yet I have knob and tube. I just can't have insulation.
    • Re: Replacing knob and tube

      Wed, July 20, 2005 - 9:49 AM
      and by the way, you just buy the fuse that fits your box. fuses are not that expensive. I'm sure you have some updated electrical panel, but if you upgrade your panel at least get 200amps and buy only fuses meant for it. I have a brand new square d main panel with my knob and tube configuration, some romex, some conduit, just make sure you use the right size cable and the right size fuse for each circuit
  • Re: Replacing knob and tube

    Fri, July 22, 2005 - 12:12 AM
    Here is an excellent book that has a section on how to graft modern wiring onto 'legacy' knob-and-tube wiring.

    _Basic Wiring Techniques_
    ISBN 0-89721-251-7

    As a convenience, I've scanned the relevant pages and put them here:

    I had a house with a renovated kitchen and bath, and saw this done in some of the basement wiring.
    • Re: Replacing knob and tube

      Wed, August 3, 2005 - 10:20 PM
      My neighbor highly recommends "Your Old Wiring" by David Shapiro. He told me to get it 3 month ago when I bought my victorian--I'm finally getting around to ordering it.
      • Re: Replacing knob and tube

        Thu, August 4, 2005 - 1:09 PM
        I'm going to be doing this very soon myself... Luckily for me the old wiring is hooked to a modern circuit breaker panel. So I plan on replacing a circuit run at a time. The big thing to be very cautious of is making sure you know whats live and whats not. When in doubt shut down the Main! As is said above... Main reasons are to get a truely grounded circuit and also to protect from over amping the line (circuit breakers job). The thing I fear is that circuit breakers are meant to protect rated Romex wires of given guages. I truely doubt that a 15 amp breaker will protect old knob and tube as it would good romex as I doubt the wiring in the knob and tube is rated the same as romex. This will be THE first thing I attend to in the new moneypit, ahem... I mean "house of my dreams".

        Thanks for the link BTW
        • Re: Replacing knob and tube

          Thu, August 4, 2005 - 9:36 PM
          I've been doing this myself, mostly outlets at the moment. I've got
          one more room left for the outlet replacement then I move onto
          replacing the lights -- that will be more fun due to the need to fish
          the wire down the walls.

          I'm going totally for replacement of all the knob and tube.

          One thing I do have to say though, looking at the knob and tube layout
          in the attic (no insulation) is pretty neat to see. But also a bit hard to
          track what is what. All my outlets I replaced from under the house up.

          Lights will mean craling into some pretty tight spaces. I guess I have to
          wait awhile until things cool down in the attic.

          Isn't it a fun project? *thunk*

          Also, the book "Your Old Wiring" was an interesting and helpful read.


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