Knob and Tube – early electrical insulation

Knob and Tube – early electrical insulation

In the time of Thomas Edison we used pocelain insulators “knob and tube” system. Rick DeLair shows us a working model with cleats, tubes and a 100+ year old light bulb with switch. John Harnden explains the influence of Czech pottery makers (Cermak Family) on development of insulators.


  1. John Does on June 6, 2020 at 4:39 pm

    Where is the neutral on that board ?

  2. TheSpazModic on June 6, 2020 at 4:39 pm

    I’m sure there will still be houses with working K & T 50 to 100 years from now.
    If you really want to see something interesting, look up how the used to wire 3-way switching with the "Carter System".

  3. Roy Smith on June 6, 2020 at 4:42 pm

    Superb and simple explanation of early wiring technology – have seen it many times. My dear old dad was an electrician – finished his apprenticeship at Standard Telephones in England in 1919. After a spell in the British Army in India (1921-1933) in 1933 was employed by the Mount Royal hotel in London until his retirement in 1980 – having worked as ‘sparkie’ for 47 years. Electricity in all its forms is maybe the greatest modern invention.

  4. Jeff Hyatt on June 6, 2020 at 4:43 pm

    Looking to buy some vintage condulets with the porcelain covers… Tks.

  5. realvanman1 on June 6, 2020 at 4:44 pm

    Very nice presentation. 

    Those antique bulbs should only be burned on reduced voltage though.  There are only so many left, and once they’re gone, they’re gone forever. 

    It also would be good to point out that knob and tube wiring is at least as safe as modern wiring, to dispel the myth (no doubt spread by unscrupulous electricians looking for work) that it should be replaced.

  6. Frank W on June 6, 2020 at 4:45 pm

    I have a roll of 10 amp fuse wire from Jefferson Electric, looks like a roll of flux core solder wire. Anyone know the application and installation of fuse wires?

  7. MrCinimod93 on June 6, 2020 at 4:45 pm

    there is a house not far from were i live that was built in the early 1900s and was wired with knob and tube at the time it was built 4 years before power was run into our village they knew electricity was on its way and planed ahead as far as i know all of it is still in use today and in excellent condition along side with the modern wiring although all 4 original circuits were are arc fault protected with modern arc fault breakers a few years ago after the 60s 60 amp entrance was replaced

  8. Chris Bouchard on June 6, 2020 at 4:46 pm

    Are you sure the reason the knob is taller is because of mice? Wouldn’t it make more sense to make it taller to make it harder to hit it with a nail?

  9. Joe Hunter on June 6, 2020 at 4:46 pm

    Why dont we use this any more

  10. Eric Wasatonic on June 6, 2020 at 4:47 pm

    Nice. Reminds me of the cleats and tubes (no longer used) in my grandmother’s attic. Were cleats and tubes ever used with uninsulated wire?

  11. Rinoa's Auspicious Travails on June 6, 2020 at 4:49 pm

    the house i’m living in, and running this computer off of is useing knob and tube, love that method tbh.

  12. David Gilde on June 6, 2020 at 4:51 pm

    To bad they would break the neutral at the switch instead of the hot.. would have saved a whole lot of rewiring and confusion.

  13. Steve Rzucidlo on June 6, 2020 at 4:51 pm

    This is a very interesting video.

  14. genuineuni on June 6, 2020 at 4:52 pm

    Thought some K&T used uninsulated wire. Advantage of current jacketed wire is the waterproof jacket. Probably K&T wiring used organic material jacketed wiring, and if wet, the copper corrodes.

  15. buzzypeterson1147 peterson on June 6, 2020 at 4:53 pm

    very cool, thanks for the video, I have knob and tube and trying to figure out what goes into rewiring, video was very helpful

  16. Mark Conti on June 6, 2020 at 4:56 pm

    I have a modest collection od early Edison/G-E, Westinghouse incandescent carbon and early Tungsden light bulbs. I have a few Wert Dimmers as well. The Wert Dimmer when used with a 40 Watt light bulb which was the recommended wattage max for the dimmer, still heated up extensively, it felt like an iron. There was no limitations, their was no Underwriters Laboratories, and many homes burned down as a result.

  17. kd1s on June 6, 2020 at 4:57 pm

    The building I live in now was knob and tube. There’s still some in use but it’s mostly been replaced with romex and 14/3 wiring.

  18. mrsamzero1 on June 6, 2020 at 4:57 pm

    Very good!

  19. migraine516 on June 6, 2020 at 5:02 pm

    The house I’m working on now is loaded with it.

  20. jay pax on June 6, 2020 at 5:03 pm

    great video…very informative

  21. Keldon Lemon on June 6, 2020 at 5:04 pm

    Very concise and well explained

  22. Mark Conti on June 6, 2020 at 5:04 pm

    ps. In comparison to todays standards and materials, I prefer the safer wiring of today!

  23. Uncle Fjester on June 6, 2020 at 5:06 pm

    good video

  24. Walter Knox on June 6, 2020 at 5:11 pm

    if you have an old house with knob and tube still intact leave it. if you want higher loads run a new electrical panel with new outlets and just leave the k&t for the already existing stuff like light fixtures. it is perfectly safe.

  25. Shawn R on June 6, 2020 at 5:12 pm

    Any mechanical device will always outperform digital. Sad to see the industry moving in the wrong direction

  26. Waiting for It on June 6, 2020 at 5:12 pm

    So informative! Never knew what these porcelain pieces were for!!!

  27. Mark Conti on June 6, 2020 at 5:16 pm

    Tube and knob was a well engineered concept of wiring, the wiring itself stood the test of time, it was Nickel wire covered in rubber then cloth wrapped, and then placed in a loose casing of burlap tubing, I have seen where rodents ate this insulation, this caused numerous fires back in the day im sure. Great piece! I will subscribe.

  28. Carl Brutananadilewski on June 6, 2020 at 5:18 pm


  29. ДУХОВНЫЙ ВОИН on June 6, 2020 at 5:22 pm


  30. gilllie666 on June 6, 2020 at 5:23 pm

    wow i hadn’t seen knob and tube stuff before the oldest thing ive seen was bare wire insulated inside of wooden trunking or duct, but this is melbourne australia, n i’m only 25

  31. Jay Valentino on June 6, 2020 at 5:24 pm

    I know this video is over 100 years old. But it’s pretty good. Very informative.

  32. Mark Conti on June 6, 2020 at 5:27 pm

    I grew up in a Philadelphia rowhouse, the third floor was never rewired, it still had the original tube and knob, their was a junction under the floorboard in the hallway on the third floor,it looked as good as the day it was installed. However, my house was built in 1900, and wired in 1911 for electricity, according to the city records that I found in city hall. The city back then required that any modifications made to a pre existing property needed to be doccumented.

  33. CampKohler on June 6, 2020 at 5:32 pm

    "Ceramic as a hole…" 🙂

  34. randacnam7321 on June 6, 2020 at 5:33 pm

    The paper is used as a spacer/gap filler to keep the conductors from shifting or kinking when the cable is bent. The nylon/PVC jacket on the conductors is the actual insulation, although paper is a decent dielectric/insulator if used properly.

  35. JohnnyRottenest on June 6, 2020 at 5:37 pm

    Yeah, knob and tube wiring is great. I guess it’s why you never hear about people wanting to replace k&t wiring. Oh wait…

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