Testing 100 Year Old Knob and Tube Wiring
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- Опубліковано 17 вер 2022
- Here is the much requested video where we test Knob and Tube wiring. And not just any wiring but wires and insulators that are probably around 100 years old that I obtained from an old house that must have been wired in the early days of electricity.
In this video we subject the wire to ever increasing amounts of current see its heating effects on this antique wire, and look at the temperatures with a Seek Compact IR thermal camera. - Наука та технологія
Awesome! This was a great test. I've seen the aftermath of failed K&T wiring, wherein someone used copper wire in place of bus wire for a rewirable fuse. The overload was due to space heaters in multiple rooms. After it happened, the wire had the exact same look, with all the strings popping off like hair! Believe it or not, the final failure for that was at the fusebox. The insulation failed where the wire went through the box, grounded out, and burned the wire off at that point.
Thanks! Wow - they were lucky that all that happened. That sure the type of undercurrent that one might expect - lost of heaters and someone upping the fuse or removing its functionality.
Interesting the wire had that exact same look with the strings popping off. Particularly so since is did one more test (next weeks video once I edit it) of the splice. The attached wire was clearly of a different type or maybe newer because the threads did not unravel like that.
Yikes !
This gave me new respect for knob-and-tube wiring. I recall the appearance of 100 year old knob-and-tube wiring in my grandfather's basement. The insulation looked very similar to 14:39 in your video, and it had an overall curly/rough appearance, and with something longer dangling here and there. I assumed that was from degradation over many years, but a high-current event could be a better explanation. Thank-you, very interesting.
You know, it could also be from degradation. Who knows how consistently they made rubber and maybe some variants melt by themselves. Or a bit of both. Interesting thing is another commenter reported a similar observation, but that definitly was after a high current event. Glad you enjoyed the video!
From what I have been told, old standards for Knob and Tub Wiring allowed for a 30 amp fuse using the gauge wiring you used. Even though this is almost double for today's standards, this actually made sense as the conductors ran separate from each other and there was a lack of thermal insulation, making heat dissipation better.
I didnt know that the standard was 30A but as you said without insulation it would be OK. Interesting someone else recently commented about having lived in a knob and tube wire house years ago where a single 30A fuse was the only fuse and supplied the house. Way back that was probably more than enough!
@@ElectromagneticVideos I think 30 amp was the main fuse and it was fuse down to 15 amps for the 14 gauge
A lot of the very early systems were lighting only so 30a would have been plenty.
@@DavidBerquist334 Typically one 30 amp main fuse and two 15 amp branch circuits.
I grew up in a house that was wired with Knob and Tube. It had a single 30A screw in fuse that protected the whole house and next to the fuse was the power meter. To read the meter a man came in the house and used a stepladder to get up to a cabinet in the kitchen where the meter was located. Just about everything ran off gas back then even the refrigerator and we didn't have an air-conditioner. Also, I don't ever recall having any electrical problems other the a blown fuse on rare occasions.
That's interesting - I didn't know of that sort of one fuse setup - must have been they way they originally did things before the idea of multiple fuses for better protection. And the meter in a high up kitchen cabinet is also something your wouldn't see today. It is certainly amazing how little power one needs if you power the big energy users on gas - I had an off-grid place years ago and had the same group of devices as you did running on propane (and the propane fridge was not cheap!). The rest of the electrical system was supplied by a 2kw inverter and generator - even less than your 30A. Your no electrical problems - from what I have read knob and tube is fine as long as it is not modified or covered with insulation - and with so little power available maybe it would have been hard to add much to the house's electrical system anyway and that kept it safe and reliable?
Similar, but was wired (badly) by the jerry-builder. The fuse box had one main 30A plug fuse and two branches that should've been 15A each but had 30A fuses in as found.
In the UK they had a similar system but it was called cleat wiring, with porcelain 2 part cleats which could clamp the wires quite firmly, so they had quite long unsupported runs just with the wire tension. It's staggeringly dangerous by modern standards but I guess people knew they shouldn't touch it.
Just looked it up - almost looks like an improvement or development of knob and tube. Yeah - standard then were not what they are now - and would be even more dangerous in the "do not touch" category with your real 230V voltage!
American K&T wiring also had cleats - use one for two wires instead of two knobs.
Very amazing video. This demonstration just might save a life. This was really an optimal situation for the wiring, installed in open air just as designed, when homes were not tightly insulated due to the fact wood or coal burning stoves were commonly used before WWII and particularly the depression era, for heating, cooking, and even heating clothes irons and curling irons, having a slightly breezy home was probably an advantage from a health & safety standpoint as coal produces carbon monoxide.
Thanks! I was fortunate to be able to get some vintage Knob and Tube stuff from a friends who were renovating a house or I couldn't have done it. I would be thrilled if this or any of my videos help someone. Yeah - the much greater air flow probably made things much healthier besides keeping wires cool. In this area we had an issue with Urea Formaldehyde Foam Insulation that was used to upgrade old houses. It stopped air flow so well that off gassing from the product made people sick. I wonder if it also covered and insulated Knob and Tube wiring in some places.
thanks for the informative video, I was really quite surprised by the current carrying capacity of such old wire.
I believe the risk with this old wiring is the degradation of the sheathing combined with overloading, but your testing seems to prove that even if it had degraded sheathing, the wire would not become dangerously hot unless grossly overloaded.
From what I have researched, it appears that the two big issues with it is a) restricting air flow over the wire and b) overloading. The original Knob and Tube was designed with the wire exposed to air to cool them when operated with larger currents. Apparently a big problem is people blowing in or otherwise adding insulation over the years which covers the wire causes it to overheat. And as we use more higher powered items these days and also additional outlets etc have have been added, the wire itself gets overloaded with currents higher than designed for. So its really years of renovation and increased electricity use that is the main problem.
I was just as surprised as you were in terms of how well it performed. I wonder how well our modem plastic insulated wire will be doing in 100 years.
I was demoing an older building too and found a melted bear wire in a ceramic tube going through floor joyces. amazing how great ceramic is at insulating against electricity and heat!
I'm always fascinated to hear about things like that. You sure cant beat ceramic other than in terms of brittleness. It in might have prevented a house fire in that situation. Cant say that for our modern plastic insulated stuff!
exactly! @@ElectromagneticVideos
Subscribed.
This was a very thorough and concise video.
Thanks! And welcome aboard!
Would be an interesting demo to see the same test, with blown in insulation, or fiberglass with the paper backing as would be a likely real world situation in an attic. Perhaps with a piece of romex spliced into it and covered with insulation. That may have been what caused the neighbors house in Pontiac Michigan to go up in flames on a cold and windy November night in 2015. For those who haven't read my post on other videos I had to evacuate the home I was renting, when the house next to me, a two story home, balloon framed, built in 1928 caught fire and burned fiercely, started in the attic by a splice from the knob and tube to romex. Neighbor stated the home passed inspection upon purchase earlier that year, electrical panel looked fairly new. Melted the vinyl siding on my home.
I remember you story. What a sad story. I will have to keep a lookout for more Knob and Tube wire. The building I got this from had had most of it stripped out years ago and what I used were the largest fragments I could find. I do have more footage of one more test - I tested the original Knob and Tube splice shown in this video - still have to edit the footage so I'll probably have it done next weekend.
@@ElectromagneticVideos next time don't touch it live ( something 9-19yo me probably would have done or super tired 😴and space cadet-me, millwright + moonlighting auto-mechanic by trade FWI, glad you didn't get sparkled ⚡or injured/dead 💀 ) at 120v-240v, otherwise 👍video, yes i also have lived in houses that had it ( yah i accidentally touch/brushed the N&T one day going into the basement,closet,attic looking for something, bad move after 50 years of decay it didn't insulate well and ended up with 1H of a sudden surprise shock ⚡almost nocked me out-cold ) oldest being 1935~ newest is the current 1970 with full electric 100A system's failure and yes i did have a fire-2017~ but minor damages and in the process of full 400A repairs/replacement's
@@richardprice5978 I really appreciate your concern! To push test currents though the wire all that is needed is very low voltage on somewhat of a constant current source. For this sort of thing I use a vintage AC arc welder controlled by a variac - the perfect setup for wire testing. So no risk of being zapped - I would never touch 120V (or worse 240V!) even though plenty of old electricians do it which in my opinions is very risky- a bit too much moisture on your fingers and bad things can happen.
You sure had a bad experience getting shocked by K&T - shows how once cant rely on the insulation and danger those wires pose in places like attics. And the fire - yikes - glad it was only minor damage!
My son's mother's home she bought around 2007, had knob and tube wiring in the attic only, the rest of the house had been updated to Romex with a new main panel, blown in insulation was done in the attic and walls, over the course of a summer, a box fan was left on in a window, which was on a knob and tube branch circuit, and the wire heated enough to catch the insulation on fire, and the home almost burned down, they saved the structure, but had to gut the whole thing, took a year to repair.
@@pinrod1 What an unfortunate example of the issues with knob and tube after a house has had improvemnets like insulation. Sure hope nobody was hurt and and the inusrance covered the repairs.
I just bought a house built in the 1960s, and wiring in the attic and going through the walls to the basement is still K&T. I’m planning to upgrade as I get time. The good news is that while more overall load is needed in modern homes, individual circuits draw less as LED lighting and more efficient appliances are implemented. The main panel was 60A fuses with several 30A fuses. The city required upgrade to 100A breaker panel before I could move in. I put in mostly 15A circuit breakers except for high load devices like A/C and clothes dryer. So far no issues, though I’m planning on reworking several circuits to add grounds. Many outlets are still ungrounded.
Wow - that must have been on of the last houses built with Knob and Tube! You make a great point about lighting drawing so much less current these days - really remarkable advance in energy conservation with CFL and now LEDs. As far as grounding goes - from what I understand replacing ungrounded receptacles with gfci ones is an acceptable alternative to grounded receptacles in many regions so that might be an an easier alternative - if you havnt already might be worth seeing if that's acceptable locally.
The knob and tube wiring held up surprisingly well. Run in un-insulated spaces it was probably safer than we would think. I wonder if that loom section used asbestos as the fabric component. The stuff on the wires clearly burned away, so that was probably cotton, but there seemed to be some loom fabric left even after the rubber had burned away. Or maybe I was fooled by ash that was holding its fabric shape, as on the wire insulation.
It was surprising. I think its good performance is attributable the ceramic insulators holding it apart and the free flow of air. The modern 14/2's plastic insulation melted allowing wires to touch in previous tests. I don't think loom was asbestos - but I was wondering. It seemed to be reduced to ash so I think it was some sort of cloth fabric. Maybe its disintegration wasn't that visible in the video. But I'm not going to breath it in to and wait 20 years to test my assumption about it not being asbestos!
I think knob and tube is better in many ways. If we used this type of system with what we know today it would be a pretty efficient system.
I think the real problem with knob and tube was overloading and flammable insulation. That system took way more than 15 amps
The cloth loom is made from cotton soaked in asphalt, knob and tube is incredibly durable, however the biggest reason for it not being the standard today is the time and money needed to install knob and tube.
@@blazenlights To be fair, a lot of the modern stuff can take more than 15 Amps too - but its really important to have a two or three times margin of safety.
@@elektro9564 You just answered what was for me a big unknown: what was loom made of! There was speculation in the comments that it might be asbestos but the way it fell apart at the end it sure didnt seem like it. Do you happen to know why the cotton was cotton soaked in asphalt? I would thought that would have made it more flammable?
Great video. We are re-doing my son's "new" 1929 wooden craftsman style house.K and T worked for almost 100 years but my first grandchild is on the way so I'm doing a total re-wire. Very interesting how well this worked safely for so long.
Thanks! Craftsman style house - is that one of the sears ones that was supplied as kit of parts that you then built yourself? Always been fascinated by them.
What a wonderful reason to redo the wiring - congrats! As good as it was/is, with the uncertainly of what has been done to hidden parts of it over the years, rewiring is the safe way to go.
I've always heard that K&T wiring was very reliable as long as it wasn't improperly modified or deteriorated. Nice to actually see just how reliable it is.
I'm sure the wood wouldn't have caught fire if the other wire wasn't so close to. But at that point the wire was already incandescent and about to fail anyways.
Yes - it only really caught fire which the current was well beyond what it was designed for. I think the real issue is things like insulation installed years later preventing the wire from having the air cooling it originally had. I wonder if our modern wiring will be as good in 100 years!
Back in the 1970's to 90's our local Radio Shack stores had a shortwave long wire antenna kit package with a roll of 70 foot bare copper antenna wire, 50 feet insulated leadin wire, 2 ceramic insulators and a pair of (possible) NOS wire knobs identical to your 100 year old knobs. they were meant for the leadin wire spacing along a wall . I used it for my crystal radio as a kid and for shortwave too.
That brings back a number of crystal radio memories for me: I had a similar antenna kit, but the insulators were plastic. For years as a kid has no success with crystal radios - eventually I found out the diode was bad. The kit I got also had a low impedance headphone which never worked. Later on I fixed all of that of course. Neat that you did shortwave - dont know if you have tried any shortwave recently but sadly most of the western shortwave services have disappeared.
I still scan the shortwave band today. I always had an interest in the more obscure, shadier side of shortwave, SSB signals, numbers stations. military communications, airliner comms and just weird and unexplainable signals I might encounter. Your definitely right about major SW broadcast stations going silent. I saw it coming since the 1990's when many US based shortwave stations were broadcasting loads of angry preacher and conspiracy programmes which, in my opinion helped ruined shortwaves reputation for the big SW broadcasters. I do still have a few crystal radios both AM an SW. I see you saw my stereo HAARP video. HAARP signals sound so much better on a crystal radio though an amplifier or recorder.
@@rEdf196 Thats really neat. I remember numbers stations from when I was kid and we lived overseas wherever dad was posted. We were in Iraq for 3 years in the pre-internet days and shortwave was the source of all current news. In those days the SW band was full of good stuff! I actually worked in the HF modem field in a previous company - we had one of the first 9.6kbps HF modems. Some of the military HF stuff you have listened to may have been our modem.
Yes - I did see your HAAP video - was always fascinated by HAARP. So do you find crystal radios actually do better for that stuff that an a superhet? If thats the case its pretty amazing!
I am very impressed. I work on my sisters 110 year old house and the KT wiring always comes up as a worry. Not any more, thanks for the experiment.
Yes - its fine if used as intended. The main issues seem to be overloading and connections to modern wire, and the wire itself being covered with things like insulation (it does need the free flow of air to keep cool when a significant amount of current flows).
great video!
Well thank you! I see your in Poland. Do you know if Knob and Tube was used in Europe, or was they some other way of wiring electricity back then?
Your test is in SUPER ideal conditions being outside and such a short length the wire can dissipate heat effectively. Only the weakest/ hottest part of a circuit has to fail; a long circuit going through lots of holes in joists and maybe an insulated attic will have hot spots that can fail. Joints and terminations often fail, but the soldered joints usually look pretty good even 100 years later. The wire is on the knobs so that it doesn't touch anything and can dissipate heat but if the house has had insulation blown in the walls or something sometimes it gets hot and burns up.
Absolutely! Thanks for the comment!
Excellent video
Thanks! I appreciate that!
Blast from the past ! Thanks
Glad you enjoyed it!
Fascinating. I’ve always felt that knob & tube was made in a time when they figured insulation would not last indefinitely. If it’s installed correctly, it can function with bare wires. Those splices right out in open space would make a modern inspector shudder, but the overall safety margin is impressive.
Your so right - as long as the ceramic doesnt get hit by something and shatter the insulation is probably better than what we have today. And those splices - they were soldered - so probably a better connection than with the various "modern" connectors.
@@ElectromagneticVideos useful trivia: the tubes, particularly the longer ones, make nice ceramic knife sharpeners.
@@lanedexter6303 Well you sure told me something I didnt know! It must be pretty abrasive ceramic? Or may all ceramic is that way? Tjis is definitly a subject of whcih I know almost nothing!
@@ElectromagneticVideos I don’t think the ceramic is unique, but it makes a decent “crock stick” sharpener. We also used to grind a round file down to a smooth rod (a tool post grinder in the lathe works well) and make knife sharpening steels. I have two houses built in 1940 (for employee housing at a hydroelectric utility) then moved to present location. They still have traces of knob & tube upstairs.
Knob & Tube was safe and performed well if installed carefully. The main danger from it was what happened to it over time. If it sagged and began touching something other than the insulators, bad things could happen. If it came in contact with something metal or became wet, the danger increased dramatically. Also, this stuff was mostly installed in attic spaces where wide temperature swings occurred.
"Knob & Tube was safe and performed well if installed carefully" - great summary of Knob & Tube - thanks!. I'll add one more thing for anyone reading this - the other possible problem is when renovations occurred and more outlets and other things were added, apparently it was not uncommon to overload the Knob & Tube wiring or connect improperly connect modern wiring to it. Not a fault of the Knob & Tube but the renovators.
interesting, my tests were not as exciting on the K&T side, the romex stuff was the exciting bit. nice work, also that isn't the cloth delaminating, but the rubber oozing through it. you're exactly right, the issue is certainly not the wire itself but the modifications done to it, or insulation packed around it
Well thank you! Your right, it did seem like the rubber was oozing out. And yeah - I would be really wary if I was living in an old house where there were sections of old wiring like that that one couldn't get to to confirm they are safe.
@@ElectromagneticVideos usually if you can't get to it, previous people probably didn't bother messing with it either, and the insulators actually make it rather safe even if the wires are bare (just not for us to touch, but inside walls it's fine and will not cause issues if left alone) Otherwise, i actually prefer K&T, i feel like it was a better system, but romex is much easier to install. (i have installed both systems)
@@gtb81. Yes - big ceramic insulators is holding wires apart and in air rather than soft plastic in romex certainly is an excellent way of doing things. You have installed Know and Tube? Wow - on what occasion? Were you able to get new parts?
Just saw your "New" Knob and Tube wiring video. How cool that you outfitted your shed in vintage wiring! Everyone take look at gtb81's new Know and Tube installation!
I am in the process of building a lighting system in my off-grid cabin with these 100 year old items, however with new cable and 12V LED lights.
So this was interesting video for me.
That is so cool - I'm sure it will look beautifully rustic. Are you using modern wire? Did you find cloth covered wire somewhere that looks authentic?
I looked at your Grimeton Alexanderson alternator transmitter video - wish I could understand Swedish!
@@ElectromagneticVideos Thanks for your reply, great fun.
Yes, I have bought twisted cable which is textile and plastic coated modern multi-strand.
Now I have to make a video about this, in English this time!
@@emilalmberg1096 That would be great! I'll look forward to a video!
@@ElectromagneticVideos I have now made a video on the topic, my wife read in an English text so you can understand!
ua-cam.com/video/DaRu4ITW5vQ/v-deo.html
@@emilalmberg1096 I just looked at your video! What a wonderful authentic wiring job for a 100 year old cottage! I'll make a few more comments on your page! Everybody take a look at Emil's link above!
You should test old cloth romex. It would be interesting to see how the old insulation handles it while also being paired and sheathed
Yes! If I ever come across some. One of my friends occasionally renovates old houses on the side so I'm always asking for old cable!
Thanks for your time and trouble
Your welcome!
I've seen that used in a house with shredded corn cob/paper thermal insulation. But overloaded wire is going to heat/burn regardless of the electrical insulation.
That corn cob/paper thermal insulation mixture sounds like a recipe for disaster if it is in contact with the K&T. I'm guessing the insulation was added way after the wiring was installed.
I just looked at your channel - wow - you have such a similar set of interests as me - looking forward to watching a lot of your videos!
@@ElectromagneticVideos I watched your electromagnetic chain video and thought this guy's a wildman, what else has he done? Got more in watch later to view. Good stuff.
@@tsbrownie I'm not really that wild which may hurt my views. I posted one burning wire video just for fun - that then developed into a number of somewhat realistic wire-in-wall tests which I did because I felt seeing what really happens might be useful and educational ..... Hope you like the other things I post :)
@@ElectromagneticVideos It was interesting, educational, and wild!
@@tsbrownie maybe that should be my one line description!!!!
Lots of knob and tube wiring was actually tin plated. This had nothing to do with soldering, though. A thin tin coating was commonly used with wires which had rubber insulation to prevent compounds in the rubber from eating into and corroding the copper wire.
This was actually a really well-done demonstration. I think it would be really interesting to do something similar, but with some of the wire surrounded by different types of insulation. One of the big points with K&T wire is that you should never insulate around it, because it is designed to operate in open air, and relies on the air contact for heat dissipation, so if you pack insulation around it it can cause it to run a lot hotter than it was intended to.
Also, I think it's interesting that this demonstration actually highlights an interesting physical effect a lot of people are not aware of: Wires under load will always get hotter where they bend than where they are straight. This is why the bit at the end that was bent in a U-shape actually got to the point where it was glowing red hot, while the other parts of the wire didn't.
I'd heard that. Someone also mentioned silver plating was used for the same reason. Any idea if that also the case, or if its just because it looked silver at least when new?
I once saw wiring on an older NJ house that had no wire nuts nor merletts. The through wiring was soldered inside the boxes and wrapped around the screws on the device. It wasn't K&T, but armored cable BX. People used to plug in toasters, hair curlers, coffee pots and vacuum cleaners in a ceiling light fixture with a screw in adapter.
How interesting and different. I remember reading somewhere that it was code acceptable to solder wires together and wrap with tape in a junction box at least at one time. I just looked up the BX cable invented date and it cable about in 1903. I am amazed it was developed so far back. That might also explain the use of light fixture as a power outlet. So the type of wiring you saw seems to have existed at the same time as K&T.
I wonder what caused one or the other type to be chosen for installation in a house? Maybe a regional thing? Maybe one or the other was cheaper?
Thanks for posting that interesting observation!
I've seen old houses that had screw-in sockets along the floor! That's the way it used to be done, screw appliances into the light socket hanging from the ceiling. The two-prong plug we're familiar with came later.
@@boggy7665 I never have seen that! But it makes sense - the screw in was the original ans presumably only common way to attach things. What a hazard if they didn't provide something to screw into the socket when not in use!
@@ElectromagneticVideos Those screw-in outlets in the baseboard had a spring-loaded flap that covered them when not in use.
@@boggy7665 Oh - how interesting - makes sense. At least there was some form of protection.
I'm old fashioned and I have a fascination with Knob and Tube. I lived in a house that had K&T built in 1914 20 years ago and last year the house had a attic fire and thought it was the K&T but from what I remember the wire coating was in good shape so might have been something else but since then been attracted to K&T.
Its funny - I'm fascinated by it too - and like seeing other old electrical stuff as well. Attic fire - yikes! One issue with K&T is when it gets covered with (flammable) insulation and overheats. Maybe that. Like your observation, the wire I used seemed in great shape.
Do you ever watch re-runs of the the old TV show MASH? Look carefully and you can see knob and tube on the OR and office walls (including one episode where it catches fire).
@@ElectromagneticVideos I have a interesting idea for a video if you would be able to it. How about a video experiment on old aluminum wire connected with modern copper wire? I had a few lights in the basement hooked up like that but switched over to all copper wiring.
@@chrisbeard5794 I would do that in an instant if I ever get hold of some aluminum wire. It was common here (Ottawa, Canada) )around 1970, and quite a few places still have it. I do have a friend that occasionally renovates houses keeping an eye out for it for me.
You were wise to switch over to copper - this issue with the aluminum (if you arnt already aware of it) is the hard insulating oxide layer that forms on the surface. That combined with the softness of aluminum and the cyclic warming and cooling at connection points results in some connections gradually worsening over time, and as the worsen the effect gets more pronounced till you end up with a sparks and flames. This is a paste to retard the oxidation and special connectors, but over time, who knows! What I really need for testing is an old receptacle with aluminum still attached to have a connection that that degraded over the years. Even then, by random chance it might just be a good connection that hasn't degraded.
I believe knob and tube wire is indeed tinned
So it was tinned! Thanks for confirming that! Do you happen to know if it was typically #14 wire of if it came in different sizes?
@@ElectromagneticVideos I think it was usually 14 gauge although I have also seen some thats larger than 16 but smaller than 14
@@TechHowden Interesting! I guess with relatively few things in a house that used electricity in those days and the air cooling of the wire, probably wasn't any need for anything larger and smaller was often enough.
Good demo! I have to say though, what you said was strings from the cloth looked like rubber extruding through holes in the cloth to me.
Your probably right about that one. Doing commentary live while making the video often means I end up not being as accurate or observant as I would like to be.
I would love to see the same test with modern wires.
I did a bunch with modern wire like 14-2 in various 2x4 walls with different types of insulation. Here is the playlist with them: ua-cam.com/play/PLHUfJmsprIcTVwSgCkTJnkinJSWrZY7DY.html
@@ElectromagneticVideos thanks!
@@pauljohnlongua4093 Your welcome! Enjoy!
great education video
Thanks!
That held up pretty good. Newer wire would have tripped the breaker. The ending was awesome.
Yes - the bright white arc making a Disney movie like star was totally unexpected - I couldn't have staged it if I had wanted to. And was really lucky I had the camera running.
Thank you 👍
Your welcome!!!!!!
When you consider the current rating for 14 gauge, its remarkable how much headroom is designed into wire. You are pushing a lot of continuous current and it’s amazing to see. Have you ever looked at how longer length wire handles higher current ? I believe your tests are mostly done with short length.
It is amazing - I have really been surprised - and for all the wire types I have recently looked at. And I guess with good reason give our homes are relatively flammable compared to brick and cement used in many overseas places.
The wires are short but I think the end effects of heating or cooling the wires are even shorter or we would notice it on the IR images with a noticeable temperature gradient towards the ends. If I were to criticize my tests, I think my main issue would be the short duration. My guess is that sustained high temperatures over a period of days would degrade most insulation types. It certainly is interesting and appropriate to consider how close to reality a test like this might actually be.
By the way - looked at your page - is the banner image one of your photos? Its great! I'm a hobby photographer too - mostly animals though.
Also keep in mind the NEC wants you to derate your wire for “continuous loads” (things that run more than 3 hours continuously, appliances, etc)
@@Solidst8dad2112 Exactly - its something like 12 amps on 14 gauge and 16 amps on 12 gauge. Its impressive how well things are designed to carry loads. What's hard to demonstrate is how this would survive in an attic where wire is next to a box of Christmas decorations or blown in insulation. I was replacing a light fixture in my garage and found a box filled with wires that fed the lights, outlets and so much. I'm glad we have over design stuff or it would not go well. I appreciate your video as is so informative.
@@Solidst8dad2112 Yes! And from some of the other experiments I did with modern wiring in good insulation, even that might be a bit much in places like attics that get really warm.
This type of insulation, vulcanised with cotton sheath, is referred to as VIR (Vulcanised Indian Rubber) in some countries. The cotton rots off, it's why it fell to bits when the rubber let go when heated, and the rubber itself can go rock hard and crumble with the slightest movement. It's more or less a case of if you find any in a very old premises you disable the affected circuits immediately and get it replaced. In Australia there was another type of insulation before thermoplastic (TPS), TRS (toughend rubber sheath). TRS is well past end of life too and is also highly likely to fail and split if moved.
I had never heard of of the term VIR (Vulcanised Indian Rubber). Just did some Googling - looks like it was use din Australian as late as the 1950s. Not sure if it was used here that recently but it would be surprising if Australian would have been much different - as you implied, we may use a different term. Also just looked up TRS (toughend rubber sheath) - looks like its similar (identical?) to SOOW cable used for industrial extension cords and similar today. Are you in Australia? Was knob and tub used there in the early days of electricity or was there some other wiring method that was commonly used back then?
@@ElectromagneticVideos Yes, Australia. No idea what was done in the really early days. I tried to post a link to a government web site that has a picture of VIR, TRS and TPS being connected to a circuit, should never happen, but youtube blocked it. VIR will have and cotton and rubber sheath and the individual wires will too. TRS is black and no cotton at all, but not all black sheath is TRS. Regardless best to not move any black sheath wiring in Australian homes. Get a sparky to check if it is TRS. Even if not TRS it will be from 1960-65 so up for replacement anyway.
@@retrozmachine1189 Thats odd and unfortunate - I say that because for the last three or four videos the same spam comment to an external website was posted shortly after the video was published and I had to delete/report it. So why they blocked your link and not the real spam, who knows. Anyway - thanks so much for you comments - its always so interesting when people like yourself post something that really adds to what was presented to the video like that. Bye the way - Australia is one of my favorite places - did a 2 month trip in a camper van (caravan to you!) up your east coast and then back down somewhat inland a bit over 10 years ago. You live in an absolutely fabulous country!
@@retrozmachine1189 keep on trying to post the video
I can only imagine an old screw in fuse box where the 15 amp fuse that was repeatedly blowing due to overload got replaced with a 30 amp or higher. Or the old penny in the socket routine. Then someone plugs in 3 space heaters. Things get very hot very fast.
You almost described what @davida1hiwaaynet saw the aftereffects of a few comments down. Sadly I'm sure your scenario was not uncommon.
back then space heaters were only 600 watts, with 3 you have 1800 watts which is only 16.34 amps but heat watts is hard on conductors. ever wonder why they used cloth power cords on Irons, toasters and broiler/rotisseries and other heat related products? 73
@@ronb6182 cloth power cords - I had always assumed it was because the more modern plastics had no been developed yet?
@@ElectromagneticVideos really in the 60s and 70s? I would think we had plastic line cords also. I remember lamp cords had snap connections for the plug and wasn't polarized. The female 3 outlet plug just punctured the line cord for a connection I had two and I could space them apart good thing I only hooked a light to it if you plugged in a heavy current device I believe you could have problems which includes a fire hazard. Bottom line we had plastic insulated wire but most was made of rubber before that. 73
@@ronb6182 I think (and I could be mistaken) that there was a significant revolution in plastics in the early 60s or so. I wonder if the cloth cords (which I remember) stayed around for a decade or two simply because manufacturers were setup to make them and they worked well.
I remember those puncture the cord plugs!
I actually came way more impressed with knob and tube wiring!
Other than the ravages of time, I think it was actually a pretty good system!
You literally had to take it to the point to where the wire became incandescent before you actually got a catastrophic situation.
I couldn't agree more! I think if used as it was installed and intended for, there are really no issues. Its really the upgrades and insulation that are the problem. I wouldn't be surprised if our fancy modern stuff doesn't last that long.
@@ElectromagneticVideos well, one thing I have seen: Is 14 gauge individual conductors that have melted themselves together inside of conduit! They are always melted together next to each other, and never to the conduit itself. So the conduit is somewhat of a heat sink, but they still got hot enough inside to stick to each other. I’ve seen them melted together as much as 2 feet in contact. Had those same conductors been in open air, I doubt they would’ve been damaged. Now obviously, it was a significant overload, but the damage was completely hidden but later led to a failure that was then discovered. I became a journeyman electrician when I was 18 years old, but now I look back when I kind of pooh-poohed those old electricians that used to say that knob and tube wiring was fine; they knew what they were talking about, and I didn’t…
@@SpinStar1956 Interesting how the conduit acted as heat sink - makes total sense but something you don't think about. I'm guessing it was metal conduit as opposed to corrugated(?) flexible plastic stuff that probably is a poor heat sink. I wonder why the breaker didnt trip.
Funny how our perspective changes as we go though life an experience things. One thing I wonder about is the use of PVC conduit for the 200A cables going into a typical home panel. I cant imagine PVC being very robust if there was a short but the old metal conduit might have kep things contained (or maybe not). Do you ever see shorts on those service cables?
@@ElectromagneticVideos well, the PVC conduit came after my time, so I couldn’t really speak to it. Also, I never did get that involved with actual power line electrical. Most of mine was industrial electrical work where the feeds were already provided. There was kind of this demarcation between the plant and the power company.
On the melted wires within the conduit, this is typically a stuck breaker or somebody circumventing the fuse in a fuse panel. The breaker will always trip long before you get a melting of the wire since as you know yourself, you have to go a substantial percentage above the normal, carrying current Before you ever have a temperature that gets that elevated.
I had an apprentice that was working with me at our steel mill, he was always complaining how I became a journeyman without having to go through all of the apprenticeship that he was about to graduate. In fact, he was at the end of a four year apprenticeship. One day, we were working in an 1100 V panel that was supplying electricity to a large air-fan system in a ore-preparation sinter-plant . They were complaining that the fans were taking too long to spin up and would often overcurrent and trip the breakers. He got it in his mind that the main connecting wires in the panel were loose, and so he took a 12 inch crescent and started to tighten them up while it was live and got his Crescent wrench in between two phases! It instantly melted the Crescent wrench in-two and gave him third-degree burns on his hand through a heavy set of rubber and leather gloves. His face was blackened, and his safety glasses had a nice green copper deposition on them. It was at that point, that I told him that this is why he was the apprentice; I never heard him complain about me, being a journeyman ever again…
@@SpinStar1956 The old penny in the fuse panel trick!
The apprentice incident That must have been something to see - lucky he wasn't more seriously hurt. Its hard to imagine the amount of energy that must have vaporized the wrench in a fraction of a second. One of my neighbors who is an industrial electrician once told me of a short that occurred on some giant power bus in a nearby plant that vaporized everything around it. Yikes!
Copper building wire was tinned because the rubber used in the insulation would corrode the copper. If you have worked in old houses with un-tinned copper you could see the rubber corroded and bonded to the copper so much so that it has to be scraped off. Remember it was natural rubber used back then, no synthetic rubber or plastic.
Loom was installed for protection from damage. It has no electrical function. As long as knob and tube wiring is undamaged it is perfectly fine. The issue with the #14 wire is the result of changing nature of households. Back when K&T was initially installed what was there to plug in? Main use of electricity was lighting, and if the owner had money, a radio. Very few receptacles were installed. Fast forward and we find people now using irons, toasters, heaters, extension cords, octopus adapters and the resultant blowing of fuses. Here's the rub, to prevent fuses from blowing 30 amp fuses were installed, and if it still blew the infamous Lincoln fuse, a penny behind the fuse. Resulting house fires gave K&T the bad reputation. Interestingly, I have been to several smaller old homes that had only a single 15 amp fuse for the entire house. How times have changed.
Knob and tube wiring is obsolete not because of #14 wire. It just is a relic of days gone by. #14 wire is still used extensively today in the NM (Romex) cable presently installed. Today's house wiring has many more circuits and receptacles to supply present needs.
It would be fascinating to see corroded copper. I wonder how long it took then to discover the corrosion problem back then.
Its amazing to think that 15A was enough for a home., but with few things that used electricity in those early days, it must have been more than enough.
IIRC they used to tin the Type R copper wire used for knob-and-tube because the rubber insulation had adverse effects on non-tinned wire. And yes, it very likely aided in soldering which was much more common back in the day.
Interesting someone also mentioned that occasionally it was silver plated which surprised me. The only thing I could think of was that one could achieve a thinner layer of more expensive silver and because the amount of silver was less it ended up being cheaper?
I live in Joliet USA and live in a 1920 bungalow. The house still has some knob and tube, mainly for the ceiling lights, and the kitchen outlets. Rest of the home was redone romex and a circuit breaker panel added. I was curious to see what the gage of the romex was and mine is 12awg. Since the home uses LED for lighting, (for the most part, still use fluorescent for my sewing room and shop) I highly doubt that this wire will ever see an issue with the LED lighting.
A 1920 bungalow - how cool! I would be a bit concerned about the kitchen outlets unless you dont actually use them. From what I have seen the issue of greatest concern is insulation over the knob and tube which was designed for the cooling of flowing air, and possible extensions being added over the years. Your lighting thoughts are are probably right, unless something else is sharing some of its wires such as the neutral. Seems like wiring back then was notorious for sharing neutrals in a way we would not expect today. If you haven't already, might be worth having someone like an electrician see if they can inspect the know and tube in the attic to make sure it is in good shape ......
Knob and tube is still common in some applications, specifically the outdoor wiring on poles owned by the power companies.
Thats an interesting comment - I had never thought about that! So I get that insulators we see on poles are bigger versions of knobs.Are tubes used anywhere on poles? The only thing I can think of is the insulators used to bring wires into things like transformers. Is knobs and tubes used in any way on poles - were you thinking of something other that what I mentioned. If so, I would be fascinated to hear more about it!
Wow ask and you shall receive - on another of your video's I wondered just that since so many comments were about air cooling vs confined insulation and it seems knob and tube actually would run cooler - albeit dangerously exposed but where I live some overhead wires are quite bare and again quite separate so they are essentially "knob and tube" as well
Yes - I responded to your question elsewhere on that. If you have have know and tube the concern is alterations and insulation covering it and insurance companies that refuse coverage. Unfortunately a rewire to remove it can also be really costly ...
@@ElectromagneticVideos They should call you quick draw McGraw ! Insurance (for all there actuary's and numbers0 often don't inspect houses like they should - it's odd - so aggressive on some things and lax on others - my problem is with the original architects that left so little room for plumbing and electrical - another 2 or 3 feet wider / longer property and we could have nice open areas for pipes and conduits - instead of hell on earth to fix thanx so much for the fast reply I'm subbing as of .....; now !
@@TotalFreedomTTT-pk9st One thing you may find it its amazing what electricians can fish though the tightest spaces. If you talking to an electrician and it seems modernizing is no practical, another thing to consider is putting in AFCI breakers that may have a chance of tripping if a hidden fault occurs. For insurance purposes, also make sure changes like that are acceptable to them and the local code. Its sad that knob and tube has become an issue.
Glad you subbed! Although you will find a lot of stuff unrelated to this on my channel!
Great video ! once that fire started on the 2x4 it's frightening - cause you could have a dead short spike up that kind current and if the breaker was broken ! hum... probably be smart to throw and test breakers every some period of time
Most breakers last a really long time. But look up FPE breakers that have had a disastrous history.
From a life long sparky: was told that that applied a zinc coating on wires that had rubber insulation like your knob & tube so the bare copper would not react with the rubber & degrade it. A few years ago at an IAEI continuing education class they told us that UL Labs went all across the USA and got hundreds of samples of various wire used in houses. All of the rubber covered knob & tube and old BX cable failed a Megger test while BX & Romex cables with modern thermoplastic insulation faired good. Was told 50 some years ago the only time knob & tube is safer is when a house gets flooded. Evidentially they would allow the knob & tube to dry out and power back up. Heard a lot of insurance companies mies will not insure a house with knob & tube.
That's really interesting about the zinc. I didn't know rubber had a corrosive effect. I wonder if is the sulfur in the rubber from the vulcanization process that over years reacts - maybe absorbing moisture and becoming slightly acidic?
I wonder if its dirt on the insulators that accumulates over time that makes it fail the megger test. Had a similar discussion about leakage currents somewhere below.
I get the drying out after flooding part but I would have thought its way more dangerous during flooding. At least with modern wires and grounded junction boxes, there is a some chance currents leaking though the water might be somewhat contained although I sure wouldn't want to be anywhere near a flood + electricity situation.
Almost looks like the rubber is oozing out of the braid as it heats up, pretty interesting.
Yes! And somewhere below a commenter was kind enough to point out the stuff in the thick loom is actually asphalt.
Well this was a super interesting test, the K&T in my house (Appleton, WI) is 16AWG so I guess the wire size is different in different areas.
Edit: I just re-measured some of it and it is 14AWG, so I must have used a stranded instead of solid gauge when I did it while I was ripping it out.
Glad your found it interesting! Someone in the comments mentioned besides #14, there also was a size between 14 and 16 (15?). Its interesting that your is #16. Do you have any idea when it was installed? Besides possibly different sizes in different areas, I wonder if larger wires may have been used more recently as more power was used?
@@ElectromagneticVideos I actually just got some out to measure it with my calipers, and it turns out it is 14AWG (measured 64mil), so I bet I used a stranded gauge when I measured it before (since stranded 16 is about the same size as solid 14). Unfortunately I don't really know when it was installed since it was at some point after the house was built, but I guess it doesn't matter since it the same anyway lol
@@wcvp And I though we could add one more wire size to the ones people mentioned :) Is you knob and tube still in use? Or is it just remnants of a bygone era?
@@ElectromagneticVideos I think it was probably about 50/50 in use when I bought the house, and it was all for lighting excluding a few 2 prong triplex outlets. I'm slowly pulling all of it as I remodel, so I think pretty much all of it is either disconnected or removed now.
@@wcvp Probably good that most of the wires to were already modernized. Re-modelling an old place is a lot of work but very satisfying (I have done it) - good luck with the project!
Those wires are found in houses during the 1900s to about I believe 1960s or 1970s when they changed the wiring insulation
So you mean the cloth coated rubber insulated wires? Were they used in conduits? I remember the old 14/2 wire that seemed to have some black tar inside and a cloth type covering.
Vulcanised rubber reacts with copper due to the sulphur content so rubber insulated wire was always tinned
Thanks for that info! I was actually speculating if that was the case in the comments below!
Or in many cases silver plated.
@@BuffyLinux Really? As in real silver? I'll have to see if there is an easy test to determine if the plating on the wire samples I have is silver or tin/lead. I wonder why they would have used expensive silver?
@@ElectromagneticVideos actually, silver plated copper wire is still preferred for some applications. You can probably tell by dipping it into a liquid tarnish remover.
@@BuffyLinux Thats a good idea. So what is the use for silver plated wire? I did read it reduces corrosion a bit, but I often see gold for that. Reduce resistance at very high frequencies for hi Q coils?
I think that oxidation you’re seeing was a tin coating for making solder easier.
Certainly could be! I have also heard that the coating (which other have though was silver) was to prevent the sulphur in the rubber insulation from corroding the copper. Quite possible multiple different coatings were used depending on the manufacturer.
If the wire is short enough you can run almost any amount of current through it. The same wire that will handle 30 amps at less than 3 ft will burn up at 100 ft. It would be interesting to see this same setup with a longer wire run.
Length actually doesn't make a difference - the heating for a given current is watts per foot, so each foot gets the same amount of power - and hence heat regardless of how long the wire is. I did a more detailed writeup here: ua-cam.com/users/postUgkxeilOfLJGy2ODslnBW0WFXUE580oHhFyP
I still have this feeding everything on the second floor of my house that was built in 1890. There is nothing up there that requires proper grounding or draws any amount of current. The bathroom however does have proper wiring and GFI outlets. It all appears to be in good condition and nothing has been added to it over the years. I see no need to replace it.
That sounds like an installation that has survived the test of time! I assume there is no insulation covering any of the Know and Tube wires?
But how much voltage could you force through this without it shorting?
Assuming none of the wires accidentally touch wood, the ceramic insulators are very good and are similar to modern ones used on power lines. It could probably sustain 10s of KV if it was just the wire knobs and tubes. The fixtures (outlets and switches) would short at much lover voltages.
Electric cow fences used to use similar insulators and and were driven with short low current pulses of a few KV (not sure of the exact voltage or what is used today).
Conduit was a great innovation.
You know, its funny to say that because a plain old conduit doesn't seem very special, but your right!!!!
They had MC cable and conduit at this time. Knob and tube was the cheapest wire. Todau NM is the cheapest and 99.99% homes are NM exclusively today.
The trouble happens when insulation is packed in by the wires. These were intended to be kept in open-air spaces.
Exactly. Used as it was intended its amazingly good after 100 years!
I wish you used an insulation Megger and compared it to the typical 600v rated modern wires.
Gee thats an intersting idea. Unfoirtunatly I dont have one but if I ever get one! It may not be a fair test since for proper Knob and Tube the wire only contacts ceramic insulators so even if the insulation has degraded a proper installation should have amazing HV resitance.
Rubber? I believe it's canvas wrap tar, much better in a relatively high temperature material. Cheap plenty and flexible to move through the
Could be! Its a year since I did that video and dont remeber the details. The smell and research I did I think pointed to rubber but I could be wrong!
That looked like a smiley face.
:)
So it's not that k&t wiring was that bad. In some ways probably a bit better, but due to mostly ignorance/stupidity people just didn't know any better. I've had to deal with it before in an old house I lived in and it was a night mare trying to figure out what side was hot and what was neutral. After 60+ years the wires turned the same color and in a dark attic it was near impossible to figure it out, but I did get it right after about 45min of tracing and trial and error before it worked again.
I would love to see this test done with modern single 14 Guage through the knob and tube wiringbto see how it fares.
Exactly! Interesting that you have first hand experience with it!
Do you mean a single modern insulated conductor from say 14/2 held by the same ceramic knob and tube things as in this test? Might be interesting to compare and see how the modern plastic 90C insulation does against the 100 year old rubber and cloth stuff.
I think the “hairs“ are not the cloth but is the rubber or oils in the rubber being heated & forced out through the weave of the cloth covering
Yes it probably is. Looking at the video afterwards it does not seem to be threads from the cloth.
Results were pretty much as expected. Although, I thought the rubber insulation would have melted sooner. Open air conductors can handle much higher amperage and temperatures before failure occurs. Inside an enclosed stud bay or an insulated wall, the rubber failure would of occurred a lower current. The voltage drop across the length of wire responded appropriately. At 20 C the voltage drop across the approximated 3 feet of wire at 50 amps should have been around .38V. (Assuming 14ga solid copper) Resistance of Copper will increase about 0.40% for every degree C above 20. FYI: Infrared light will become visible when it reaches a temp of around 800C (1470F). So at 90 amps when your camera was maxed out, the actual temp was over 800C with the red visible light. If the conductor had not failed, the visible color would eventually change to white, then blue as temperature continued to increase.
Yes - no huge surprise. As far as the insulation goes, I wonder if 100 years of ageing mage the rubber less easily melted.
Great temperature estimate approach - 800C is really quite astonishing. You got me thinking - maybe with a bit of calibration one could do a pretty good black body radiation color to temperature app similar to the IR camera output for the RGB phone camera for temperatures beyond what IR normally does.
Great video thanks for making it.
I do have a weird question, are you wearing work boots?
I ask as I know someone who was working in old house and touched old wire and current went into arm down body to sock feet and into ground.
He said it was very painful and advised me that I should always wear good work boots or thick rubber shoes.
Thanks!
No - not wearing boots. But here is the thing: I'm using isolated low voltage for these tests (see ua-cam.com/video/CP3-jcpzZeI/v-deo.html) so in the setup where I have it I am not going to get zapped.
But - Your friend has given you some really good advice. Good thick rubber soles will provide an extra level of insulation to protect you, but not something one should not rely on. Another is to use a fiberglass ladder if your on a ladder which is also insulating.
Shocks can be painful, but worse, paralyzing and potentially lethal. So always take precautions when doing things like renovating. And when knowingly working with electricity, don't do anything you are not sure of or have any concerns about.
The wire must be close to the old Australian size called 16 which was 1/064 (1 strand of 0.064 thousands of an inch square) whose rating I can't remember, I think 16 amps but we used it sometimes in 60 amp fuses and I think it used to blow at 100 amps.
I didn't know Australia had historically their own wire sizes - Im guessing over time we all just began to use US sizes because of their dominance in the market. Interesting about using it as fuse wire - a few commenters have mentioned that the us #14 bare wire used in knob and tube was often fused at 30A because the air cooling allowed it to carry more current. Was the wire covered with insulation when used as a fuse? I remember seeing fuse boxes as a kid with replaceable wire that was surrounded by woven asbestos fabric!
@@ElectromagneticVideosbelieve Australia had similar to the U.K the Standard wire gauge a British units (SWG) till we went metric and used mm squared and rewireable fuses. Which was simply just bare wire put into a fuse carrier. Ours were covered in ceramic but one part of the way to view of it had blown was exposed . Then that was inserted into a fuse board with some asbestos pad material covering the hole. Google Wylex fuses they were our mainstay from the 60-80s. Still many in use today. Safe I’d used for overcurrent properly but many would wire it with the wrong fuse wire size. 60 amp would be 1.5mm wire 16 awg for tinned copper fuse wire. But residential would mainly use just 5,15 and 30amps in the U.K.
@@lukedoherty8062 You just brought back a mmeory for me: When I was a kid we lived in South Africa fo ra few years and we had rewireable fuses just like you described - asbestos pad and all. I remeber dad changing the blown fuse wire, and there were a number of different wire sizes each wound around a piece of cardboard presumably with the amp rating marked on it. I googled wylex fuses and some were very similar to what I remebered.
We had the same probelem here (Canada) with people putting in larger replaceable fuses whne one would blow.
Interesting that you changed how wire was measured whne you went metric. We kept awg and many other things becuase of our US neighbours. So we really usea mix of systems these days.
What is IR camera you are using?
It is the Seek Thermal CW-AAA USB-C one that plugs into an android phone. For anyone reading this, you have to be careful to make sure the one you get is right for your phone OS and connector - the part numbers are very similar.
... knob and tube was made In a factory in huge quantities. Of course it was standardized, I don't know about the quality control of the insulation but the copper was expensive the wire gauge would have to be precise to even know how much to sell the wire for
You know, I never really thought about the large scale manufacturing of it, but your right. And the insulators I had were clearly shaped in some sort of mold and I think some even had writing indented on them. Getting thing precise back then must have been a challenge.
Be interesting to see a comparison of knob and tube verse Romex have a rig setup with half Romex and half knob and tube and see which fails first
Based on the previous tests,. Romex would probably fail first - the soft plastic between the cables melts and the cables touch before they get hot enough to melt and arc like the knob and tube.
Interesting - for steel you have a BH curve that is non linear and I wonder if that is true or copper and aluminum such that staying below XX current produces very little heat but at some threshold higher the heat really goes up - again in a non linear way I plan to put two microwave transformers in series such that each only see's 60 volts - tie the 2ndary's together to get the 2400 volts why ? because the transformers are physically too small and go too far up their BH curve into saturation - and that is where that high current buzzing comes from - so maybe you can get a quieter cooler unit that way that's the idea anyway
The BH curve is typical for Ferromagentic metals. Copper and Al will have essential a straight line BH graph that is way below the one I showed which si why we dont make magnets out of them.
The microwave transformers should not be in the saturation part of the curve. See my transformer videos. Be REALLY careful with the microwave transformers - the kilovolts out of them is lethal. Consider using a dead mans switch to keep yourself safe. I gather a number of youtubers/viewers have been killed/maimed by unlikely events like falling onto HV microrovave transformer circuits.
@@ElectromagneticVideos Thanks on the microwave transformer advice - I know I know - I'm prepping up with meters and all my caps are going in new PVC containers with no ability to have two connections close - it all sucks - that 60 hz buzz scares me- I lived in a damp basement for like 12 years with purposefully negligent extension cords on the ground - why ? not sure - but 3000 comes to grab you I guess - I am not playing sparking Tesla stuff - one hand operation also - and I am not experimenting there is a goal and that's it - thanx again
@@ElectromagneticVideos I thought that they naturally close in on saturation at full voltage - my current meter shows current draw is negligible until about 90 volts and then goes up quite a bit - so my reasoning is that yes - it has moved into the crap part of the BH heading towards saturation - no ? and so two in series would keep each down at 60 volts - anyway I'll report my results thanks again for responses
@@TotalFreedomTTT-pk9st Its a cost compromise - typically the top of the sine waveends up somewhere in the knee of the curve. More so for short term use things like a microwave. One would expect the idle (called magnetization) current to be some fraction of the full load current. My guess would be maybe 5 to 10% although maybe more for a short term use device. Since that current is mostly reactive, the current doesn't result in much power being consumed.
K&T no. 14 is rated 20 amp in free air iirc.
That free air bit seems to be the key. From what I have read on of the main problems is over the last 100 years of renovations air flow gets blocked and/or it gets covered with insulation and bad things happen :(
Some areas require arch fault breakers.Also 15 amp breakers max.
I would certainly suggest arc fault breakers for knob and tube even if they are not required. How much additional safety that might add to a knob and tube installation that may have been subjected to renovations over the years is perhaps up for debate, but if replacing knob and tube is not an option, its at least somewhat better than nothing :)
👌👌👍👍
Thanks!
The real question is how much electrical leakage is there in a whole house with knob and tube...can one expect in an old house to lose several watts 24/7?
I'm not sure what you mean by leakage. If you mean the restive power loss when current passes though it as tested in this experiment, it would be no different from modern cable of the same size. If you mean leakage current though the insulation, I would think hardly any due to the ceramic insulators.
I've heard that on old k,t wiring,,,dust/dirt accumulating within cavities does conduct a small amount of current, ie electrical leakage, and with hundreds of feet in a dwelling, you do use a little tiny bit, which adds up over time......maybe this is a mith I heard somewhere?
@@brandtfj That is very interesting! You know, there was a lot of dirt on the knobs and tubes. A hundred years of dust! And with a bit oh humidity it could conduct just a bit as you said and then add up all across the house. Maybe in an old house with no vapor barrier drafts could easily deposit moisture on some insulators. I guess the problem could be that if enough current flows along on insulator it could carbonize the dust and create a conductive path that could get hot and cause a fire.
Funny - it reminds me of a place I once stayed it in Florida. The was a power pole neat the condo with the upper lines being at least a few kv. Salt and algae would build up on the insulators and from the ocean mist and you could hear it sizzle. Every now and then a huge spark and bang would lean it off. Same sort or trickle current on a much larger scale.
The cloth covering was probably asphalt impregnated. That may be the smell and cause for disintegration
It seemed more rubbery. But you could be right!
@@ElectromagneticVideos The insulation next to the copper is rubber. Then it's protected with asphalted cotton covering
@@grounded-b937 Oh! Interesting! I didn't know they impregnated the cotton with asphalt. Do you happen to know why? Maybe to keep the rubber from hardening due to exposure to the air?
@@ElectromagneticVideos I believe it was to protect the rubber from abrasion. Just like the old timers made up splices on Knob & Tube - twist the wires, solder, apply a layer of rubber tape then a layer of "friction tape". Which basically cotton tape impregnated with asphalt.
@@grounded-b937 Is that what friction tape is? I didn't know the black on it was asphalt. On the video with the splice the splice was definitely covered with friction tape.
Th3 cloth is not "falling off", it is the contrary: The cloth is intact, but the (near) liquid rubber is pushed through the eyes in the cloth weave into forming these thin hairs.
I think your right! When doing a video like this and observing things live for the first time sometimes I dont see things that closer ofservations of the video do. Thanks for pointing it out!
Old school science experiments. Same type Ben Franklin or Thomas Edison would have done, except the thermal camera
Yes! There is nothing like sometimes doing an actual experiment - really brings to life!
11:04 Spider also thinks it is getting to hot, time to move to a new house.
Ha yes! Poor thing.
Try putting a container to hold in and fill with blown in insulation .It should warm up
It sure would - I didnt do exactly that but did some videos with modern 14-2 embedded in insulation. The resulting safety margin was concerning!
K&T did not have rubber. It was tar or bitumen mixed with cloth. The MAXIMUM amperage is 15 amps. The wiring is perfectly fine if kept at 15 amps it’s entire life. K&t is actually safer than romex for obvious reasons. Just got expensive and when insulation technology as well as wire technology improved they went with romex.
This test though not advised is actually quite impressive and shows that they cut no corners in quality back in the good old days.
What I find amazing how well it held up afte 100 years or so. I have moderm plastic insualtion get brittle afte a fraction of that time.
Safer than romex? I doubt that. What is your source for only rated for 15 amp circuits
@@chrishall2594
Aside from that factor it is MUCH safer.
My source: common knowledge. K&t was supposed to be suspended in the air. The hot and neutral were on OPPOSITE sides of the room coming in only to connect lights and the like. They made higher amperage conductors back than, just didn’t need them for the electrical demands of the good ol days so it wasn’t used except in commercial applications. They weren’t as stupid as one might think back than. Illiterate perhaps but definitely not stupid. They had the right ideas except for neutral fusing. What they thought would be double safe turned out to be the opposite as the neutral fuse normally was the one to go.
So technically yes the concept of K&t was and still is safer than having hot and neutral in the same jacket to cause shorts should one conductor lose its insulation. They thought of it believe me.
The real reason why K&T went out was due to cost.
Same can be said with fuses vs. circuit breakers. Fuses ARE safer. That’s why the UK has every plug with a fuse. It’s peoples stupidity (ie: higher amp fuse or stinkin Lincoln) that did away with them.
The wire is tin plated so it will be easy to solder
Plating was apparently also to keep the Sulfur in the rubber insulation from corroding the copper.
Looks safe to me.
I thin it generally is was as long as it wasn't covered with insulation or had improper modifications done to the system over the last 100 years.
I don't think todays wire casting would have kept as well
Completely agree! I have see NMD wire plastic insulation get brittle after perhaps 25 years of installation. With the ceramic Knobs and Tubes holding the rubber insulated wire, the lifetime of the wiring seems much longer!
9:34. Wife decided to watch with me.
I think it's a shame that K&T has such a bad reputation these days. People forget that it was initially phased out because it was too labor intensive, rather than for safety reasons. It'll be interesting to see how modern Romex will be perceived in 70 or 80 years, since it is a lot more insulation dependent than K&T, and is just as susceptible to homeowners doing scary ass things to it. Who knows, maybe a new and improved version of K&T with protective ground and AFCI breakers will be developed in the future if repairablity and sustainability is taken more seriously
Yeah. Its amazing how will it had survived 100 years of service and along as it was used the way it was intended. I have seen some older Romex in some houses I lived in where there is noticeable brittleing of the plastic insulation where it is outside of the plastic sheath in junction boxes. I wonder what the entire Romex cable - sheath and insulation - will be like in 100 years after the plastic has aged. Although I think your hope of a future K&T is unlikely - labor is just too expensive.
One interesting thing is many homes in Europe have wire in conduit, I think because of the brick and concrete walls which seems much better for future-proofing. Although maybe they have by now copied us doing things as cheaply as possible .....
@@ElectromagneticVideos I've seen that with rubber-cloth insulated wire, the insulation can be wrecked where it was in boxes above surface-mount light fixtures. The tungsten filament bulbs produced tremendous amounts of heat. Outside of where it entered the box, the wire appeared to be in good shape. It's not until recent decades that high-temp capable insulations became the default in cables.
@@boggy7665 How interesting - you can sure see how years of heat gradually degraded it. The limited amount of wire I got didn't show that but was not from light bulb fixture. There were some in the old shed - wish I had though or known about what you describe - I would have made the effort to get one which were hard to get at (lots of stuff stored in the shed).
I have seen even "modern" cables maybe 50 years old where the plastic insulation insulation gets brittle in the junction box. I wonder if plastics have improved since then?
@@ElectromagneticVideos I'm not an expert but was present when an electrician rewired our 30A-120V service to 100A-240V in the 1970s. The wire that came in single coils or that was in armored cable then was type TW, plastic, rated to 60 °C. Surface-mount light fixtures came with warnings to use 90 °C wire in proximity-- not sure how you were supposed to do that when the cable was 60 °C. I guess, don't use those fixtures... but widely ignored I'm sure. Today's common wire is type THHN which is rated 90 °C. Like I say... subject to criticism by an expert.
@@boggy7665 Wow - 30A - how times have changed! Interesting about the 60C where 90C is was required. I'll bet it was simply you used whatever fixtures and cable was available and the electrical inspectors accepted that at the time. I think almost all NMD cable is 90C these days ....
Personally, if I had to continue using any knob and tube, I would just use it for lighting only. Keep the load well under 10 amps. I wouldn't use it for receptacles, certainly not kitchen receptacles.
Year if one could be sure it was only connected to (LED) lighting at low currents its hard to imagine how it could overheat and cause a problem.
The tin coated copper wire is referred to as copper clad wire
I thought copper clad meant the wire was coated with copper and the inside was something else. These days the inside is often aluminum. Has the meaning of the term changed over the years?
Arc fault circuit breaker at 15 amps and box /oulet safety checks... done deal fir you all. You are welcome.
Before we mock our predecessors as dangerous lunatics surely this demonstrates that actually this system is substantially OVER-engineered. Even today there are few better insulators either thermally or electrically than glazed ceramics. By using knob and tube stand-offs the designers have recognised the shortcomings of rubber a couple of decades before PVC became common, and In an age when the only common domestic appliances were flat irons and radios (and of course 25W lamps) this installation has far exceeded it's remit. I would like to see a control conducted with modern 15A cable passed straight through woodwork to see how quickly the house burns down lol
So true!!!!!!!!!! Used as it was intended it really is way better quality and long lasting system than what we have. In some old houses I have lived in, I have se how "old" plastic wire insulation (25 years old) seem to brittle particularly near junction boxes (air exposure?).
I did some experiments like you suggested last summer. Here is a link: ua-cam.com/video/U2sLO1noD2o/v-deo.html
@@ElectromagneticVideos Great link thanks, I should have guessed you had already done this!
@@robturner3065 It was a bit of an eye opener to me - particularity in the following videos with building insulation around the cable. I was actually not to thrilled to discover that in places like a hot attic in the summer, a wire embedded in insulation has little margin of safety.
You could probably take a baseball bat to a caveman and not be surprised that ancient flesh behaves just like modern man’s.
After soldering a joint, it was wrapped with rubber tape, which would subject to abrasion, and then wrapped with “friction tape” to prevent damage to the rubber tape. Try finding friction tape nowadays.
I retired in 2020, and one of my jobs was a cashier at a local hardware store, we still carried friction tape but it was usually purchased by hockey players for use as grip tape for hockey sticks.
Now that you mention it, I haven't seen friction tape in the last few years...
Do in a house you have several hundred feet of that wire and if you have a big load at the end of the circuit you would have more heating because it's a longer run a wire I believe ask a certified electrician but I would say don't put any more than a 15 amp fuse on the 14 gauge wire or a 20 amp fuse on the
Somehow your comments got truncated, but you seem to be asking about large loads on #14 house wire:
House wire #14 should never normally be used with a fuse or breaker larger than 15A. And the largest continuous load should be no more than 80% of that.
Your also right that the longer the wire, the more heating loss you have and that really does get important for large loads because the that heating loss is due to the large current though the resistance of the wire resulting in the voltage at the load end of the wire dropping. Many electrical codes do not allow more than a 5% drop, so with a large load and long wire on a 15A circuit, you may need a thicker wire such as #12.
I did some experiments in other videos with the 14/2 wire inside walls with insulation. The safety margin drops significantly under those circumstances, so much so that if I was building a house today I would probably go for #12 wire for the 15A circuits to increase the safety margin. I gather some builders routine do that.
Information about whats permissible and best practice/safe in your location is best obtained from a locally licensed electrician. So please consult with one if you are planning something like a large load attached to a long wire.
That's not the cloth coming off, it is the rubber/plastic oozing out if the porous cloth cover from underneath it...
Just looked at that part of the video again - you may be right. The spirally things did not seem rubbery but it could be they just cooled upon air exposure and hardened. Now I wish I had examined them more closely.
Here in New York, old knob and tube was fully exposed….
You mean in living areas?
I find the way you talk about the wood temperature to be potentially misleading here... Like, e.g. at 13:22, you say the wood is being kept relatively cool, but it's at... oh, if I can guess based on an upside-down scale, maybe about 50°C in large spots, which... yeah, that's a lot cooler than 85°C of the wire, but it's above a previous threshold of the wire temperature being at 37°C, which you already were talking about being warm. (I mean, it's body temperature, so not that warm, but still.) Just thought I'd point this out.
Fair enough! I certainly wasn't intending to be misleading. I do find that when narrating things while I do them, my words are not always as precise or clear as I would want them to be.
@@ElectromagneticVideos fair enough! Well, something to keep in mind for if/when there's a next time. And no worries! I definitely didn't have the impression that it was intentionally deceptive -- just open to an easy potential for misunderstanding.
@@DavidLindes No worries - I always appreciate comments clarifying or restating something that wasn't as clear as I had hoped! Hopefully it will help a future viewer!
@@ElectromagneticVideos Indeed, that's the hope! ❤
I put an afci breaker on it about best you can do
Agree with you 100%. If I lived in a place with K&T thats exactly what I would do if I was reasonably sure the wiring was as originally installed and being run with reasonable currents.
Your calculations in converting Celsius to Fahrenheit are very rough estimates. 2:1 is not very close to 9:5 , which should be 1.8:1.
Your right! Doing conversions like that as I film a video often means I cut corners - too many things going on at once!
I’d almost bet that the loom was made out of asbestos. As much hype as it gets I doubt handling a small amount like that would cause you any problems, but be careful nonetheless!
I really appreciate the caution/warning! I was wondering about that myself. But in the end I don't think it was not because it essentially burned up much like the insulation. I think it it is some sort of (no asbestos) fabric. I'm also wary of the potentially toxic fumes which is why I have been doing these experiments outdoors.
@@ElectromagneticVideos that’s a good point. I’m no expert but if I recall correctly it could be cotton/ linen, or asbestos. They either changed it at some point, or like you were saying with the non existent standards, each manufacturer did their own thing. Either way, I absolutely love your content! Proof that you don’t need a huge production with super expensive equipment to make enjoyable entertaining content, thank you!
Also curious, even though the amperage is the same, wouldn’t the lower voltage output of the welder effect the total power delivered to the wires? loaded output of the welder is likely to be less than 30v, and with home electric at 120v, 10 amps of each equals a substantial difference in wattage. I’m not familiar with how these components are tested or rated, but do you think that repeating some of these tests using something like a generator load bank at 120v would produce the same results, or do you think the wires or components would fail at a lower amperage?
@@Kc12v140 Interesting - maybe even depended on if the were near an asbestos mine or not. Asbestos sure would have been the perfect material for it given the hazards were unknown.
So glad you like the experiments. Funny - I got the old welder at Habitat for Humanity reStore a year ago after its price had kept being reduced because no-one was buying it (AC only is think was the turnoff) . At $100 I couldn't resist even though I have MIG. I had no idea I would end up having so much fun with it.
15 A
Caution the cloth may contain asbestos!
I really appreciate the caution. I did a fair amount of research before hand and am pretty sure the fabric used in these wires was cotton. That said, also made sure to do the experiment outdoors and being upwind of the fumes while doing the test!
Those wires can take up to 60 amps of current that's why they call it 60 amp wire
Do you mean #14 wire used in Knob and Tube was originally rated at 60A? If so - wow - and I guess the insulation has deteriorated over time and sure cant handle the resulting temperatures any more.
VIR is the worst insulation devised. It makes me feel sick looking at it. I know the sick smell... can almost taste it from watching this.
This is why I loath working on domestic wiring systems, that often include layers of DIY = DIE wiring too.
The worst fumes were from the overloaded extension cords in an earler video - these were nothing in comparison. I`m sure Knob + Tube + DIY really often sets up things for DIE.