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20

Knob and tube wiring uses two separate copper conductors, each isolated by cotton cloth or soft rubber. The conductors are strung tightly through the cavities of your walls and floors, and depend on being separated by air in order to avoid overheating. When going through joists, the wires pass through porcelain tubes. In the wall and floor cavities, they ...


18

Generally, it is a good idea to replace it, especially if you can easily access it. One thing you don't want to do, is replace part of a circuit. Then the next guy might see the new romex and make some assumptions about the rest of the wiring. The other time you really really should replace it is if it runs through insulation, especially blown-in cellulose. ...


17

The advice my family once got from an electrician on this question was that if you have low amperage service and NEVER touch it, you're probably okay. If you have regular electrical service or touch the circuits at all, remove ALL of it. His basic theory was that if you keep the wires cool, and they haven't caused you trouble yet, it's unlikely to cause a ...


13

Myths abound about K&T, and lots of it is ripped out unnecessarily. The K&T wire is exactly as thick as modern wire, and was installed by skilled craftsmen using bulletproof soldered joints rather than plastic wire nuts. The ceramic tubes will outlast civilizations. With certain important exceptions your K&T will outlast the house itself, ...


11

If you need a receptacle that can accept a grounded plug but don't actually have a need for grounding, you have two options: (1) a GFCI-type receptacle marked with the words “No equipment ground,” and (2) a three-prong outlet protected by an upstream GFCI and marked with the words “GFCI protected” and “No equipment ground”. See section 210-7(d)(3) of the ...


9

Take a look at the diagrams in the Wikipedia article you linked to. These will tell you what you're dealing with. There are some big red flags that are easy to look for: First, kill the power to this circuit at the panel. This will allow you to poke around in the wiring safely. Use a non-contact voltage tester to make absolutely sure there's nothing live ...


9

Yes, you can leave the knob-and-tube wiring in place. Labeling is neither required nor common, but if things are confusing enough that you think it's warranted, it can't hurt. It's also a good idea to rip out whatever wiring is accessible (e.g., in an unfinished basement). If you have an electrician do the disconnection work, you should ask the electrician ...


8

Use a NCVT (non-contact voltage tester) and see which of the two wires alarms when the switch is on. That will be your black/hot wire. If both of them alarm, stop, do not pass go, something else is wrong. For the ground, you don't have one. The safest thing to do is run a whole new wire back to the panel. Anything else is "less than safest".


6

I think it's very common to leave disconnected knob-and-tube wiring in the walls. Leaving a note sounds like generally a greate idea, but I didn't understand where you intended to put the note. I think the most important thing is to label the circuits going out from your distribution panel so it's clear which circuits still have knob-and-tube wiring. If ...


6

A house in San Carlos CA, Having 50% knob-and-tube, 50% 1980 romex: Insurance was no problem: No company cared (I ended up getting it from Travelers, via GEICO). So, I wouldn't let the insurance stories scare you until you pick up the phone and ask. What they do care about is the type of Circuit breakers you have. The modern ones that look like switches, or ...


5

The correct answer is: Redo the wiring all the way back to the panel. The workable answer is: The wire with the black stripe on the insulation is BLACK. The other one is white. The junction box is probably not grounded, but I'd attach the ground wire of the light to the junction box anyways. Safety wise, the ground isn't entirely necessary on a ceiling ...


4

Arc-Fault Circuit Interrupter (AFCI) An arc-fault circuit interruption device is designed to detect dangerous arcing within the protected circuit, and open (turn off) the circuit to prevent damage caused by the arcing. It does this using special circuitry to analyse the electrical characteristics of the circuit, looking for characteristics that match ...


4

There may be issues with your insurance company. I recently bought a house and asked two insurance companies about the knob-and-tube wiring. Liberty Mutual said that they would insure the house, but would require that the knob-and-tube wiring be removed within 30 days by an electrician. Met Life said that they would not be able to insure the house until ...


3

Per code, you have to have a separate ground wire if you have a grounded outlet. Replacing the old wiring is the best, but it's a big job. Removing all the old wiring would require you to open up a lot of your walls because the wires will be secured at multiple spots with knobs, and you may have splices at unexpected places that prevent you from pulling ...


3

The typical process of disconnecting an unused wire while leaving it in the wall is to join the hot(s) and neutral at each end so that it's obvious that it's unused and any attempt to reconnect it would trip a breaker. And I hope that no crazy electrician would ever want to reconnect an old knob and tube line. I would take the extra step to completely remove ...


3

If you can insulate the walls without a "material that envelops the the conductors", then sure. But I would think that wouldn't be a very well insulated wall. Knob and Tube wiring is meant to have an area of free air about it. Insulation encroaching on this space could cause the wiring to overheat. National Electrical Code 2014 Chapter 3 Wiring ...


2

The answer changes depending on location. Because of a complete lack of actual fire incidents, four Western USA States: CA, OR, WA and ID petitioned for an exception to NEC 394.12 and permit insulating over Knob & Tube Wiring. In some places you must first file a Knob-and-Tube Wiring Safety Report, and everywhere else it's a good idea. It is a ...


2

In this case I would carefully remove any cotton or cloth covering on the existing wires, after shutting off the branch circuit. Hopefully this leaves you with a rubber or plastic layer, but either way it will be ok. Now push those wires back into the ceiling as much as you can. Mechanically rip that entire metal electrical box off the building. A ...


1

An AFCI is a great addition to K&T wiring. While the conductors in K&T are separated by large distances, and even studs, they do come together at junction boxes which are often metallic. An AFCI adds a layer of peace of mind to the situation. Be sure to measure your K&T wire to determine gauge. It can take slightly more current than the modern ...


1

Knob and tube is no longer listed and approved, it should be de-energized and abandoned when encountered within the scope of any new work after being replaced with listed cable assemblies suitable for the location (in your case, non-metallic bonded cable, aka Romex). That said, it sounds like what you have in the box used to be a switch leg where the ...


1

Really, you should just replace the Knob and Tube completely (at least where you can). In Ontario, you can't even get insurance if you have knob and tube. (In fact, when I bought my house, the insurance company required me to replace the fusebox with a breaker panel within 60 days of moving in.)



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