[Swtinnct72]

First let me say hello everyone and second let me tell you all that I am very new to knob-and tube wiring... I hope I can explain this enough to get some help from you all.

Ok here goes... I have been trying to figure this out for some time... I wanted to replace a ceiling fixture in my dining room which I thought would be as simple as replacing a normal outlet which I have experience in doing... I removed the old pull chain fixture only to discover the knob and tube wiring, I want to add a switch to this configuration but don't not know what wires to connect or what type of switch(i.e. single pole/double pole) I need to connect it all with, I have managed to run the wiring for the switch but as I said I am unsure of what comes next... any and all help is very much appreciated...

[darkmas]

Hello. Ironically I just spent all of last weekend helping a friend rip out all of his knob&tube wiring from the attic and replacing it with modern wiring. I've still got the battle scars from shimming about in the attic on my stomach. :-)

Let me first say that depending on where you live and what year the home was built, the wire itself may well be aluminum and not copper. At which point you have a serious fire risk in any attempt to interconnect aluminum (old) with copper (new). We didn't know enough about the laws of physics back in the '20's and 30's to understand the galvinzation/oxidation effects of passing electricity across a junction of two dissimilar metals such as copper and aluminum. Such effect being that a small amount of resistance occurs between the dissimilar wires due to the corrosion of the aluminum; this leads to enough heat buildup to literally ignite things like wood. Aluminum wire is illegal to use in new work these days per the NEC, and safe, approved junction units are on the market today for interfacing old (aluminum)with new(copper) work.

So, honestly my first recommendation is to call in a pro in this case, because you probably need to replace the knob&tube wiring for this fixture all the way back to the source of power, which I'd guess is a fuse box, either with screw-in fuses or the good ol' tubular fuses.

If funds are short (and you don't happen to have a brother-in-law who is a licensed electrician), you may want to forget the idea of a hard wired light switch and get a simple x-10 based wireless switch and screw-in fixture lamp module. Radio Shack sells most of this stuff, otherwise you can order exactly what you need online from a number of sources, easily for under $30. Unscrew the light bulb, put the lamp module in its place and then screw the bulb into the module, put batteries into the switch, stick the switch on the wall with double sided tape and you're done in less then 10 minutes.

You can do the real work yourself if you really want to do it correctly, it's not that difficult. This first thing to do is to determine if the wire is aluminum or copper. This easy to do, aluminum wire doesn't bend easily like copper. The best test is to simply take a bit of sandpaper to the bare end of one of the old wires and clean off the residue/oxidation. If it looks like aluminum (silver in color) then it's aluminum. If it cleans up to look like copper (a goldish/brownish color) and it bends easily and holds its bent shape then you've got copper K&T, you're lucky in that you don't need to replace the run back to the fuse box, and, if you're still reading this at this point and reply, then I'm happy to help you wire the new switch, which will be a piece of cake, relatively speaking.

-Bill

[Swtinnct72]

Thanks Bill, and yes it is copper that was the first thing I checked because two other very near by houses caught fire because they had the old aluminum wire... most of the outlets have already been rewired and the k-n-t is only in the attic... and I have had the "fuse" box replaced with a new "breaker" box... so I am all set to get dirty... lol

[letmetellu]

If you disconnect the two wires that go to the pull chain that you have now, those will be the two wires that you will work with.
Connect one of the wires that you took off the pull chain and connect it to one of the wires that you ran to where the switch will be, then install a regular light switch. It will be a single pole switch, and will only operate the light and fan as one unit. If you want it different I will explain that later. Now back to the wiring, after you have connected the switch go up to the box where the light will be, Use a wire nut to insulate the two wires that you connected together. Now you still have two wires that you will use to wire up the light and fan. In the fan and light wiring there will be wire marked light and a wire marked fan and then another wire which will be the common. Connect the fan wire and the light wire together to one of the two wires that are in the box connect the common to the other wire in the box.
Now if you want the fan and light to work separately then you will need an extra wire to the box where the switch is and you will need another switch. Then you will have three wires to work with in the box where the light goes. This time you will not connect the fan and light wire together. The fan wire will go to one of the wires coming from the switch and the light will co to the other wire coming from the switch. They make a switch that is a double switch that will fit in a single duplex box. On one side of the switch you have a bar that connects both switches together. Make sure that one of the original wires that was connected to the pull chain is the wire that is connected to this side of the switch. The other two connect, one to the fan the other to the light. This way you can turn either one on or off at the wall switch.
This is hard to tell you about by typing . If I had a way to draw it out it would be easy for you to see. If you have any questions let me know.

[labman]

I agree you need the help of a real professional. This is sort of a tricky, technical code question. Fortunately, we have tkrussel here. I wouldn't do anything till he shows up. For a long while I was giving the best answers here I could, but since he showed up, I leave it to him.

[jpob]

I have a similar sit uation and would like to see a diagram.

[Crafty1200]

Do you know what year this house was built? I'm a general contractor and have worked in several hundred houses over the years. I've been around a lot of knob and tube wiring because of remodeling a lot of kitchens and bathrooms. First of all is this an existing ceiling light metal junction box? Does it have a separate black and white wire coming threw 2 separate holes in the box with a black tubular insulator, which is called loom. If you have that configuration then you should already have a switch in one of the nearby walls because of this type of home. They never put a hot set of leads into a light junction box.. it was never done back when this house was built. So if you can't find a switch more than likely somebody put the two wires together in the switch box and made it to where there is power to the light box all the time. Then they patched over the switch box. If you have attic space you can go up in the attic and find the light box. You'll see a black and white wire coming out of the box. If you follow the black wire to where it turns down and goes threw the 2" x 4" top plate. Usually the switch box is just below where the wire goes threw the wood. More than likely the switch box is next to the door leading to the room and the side you enter buy. You can tap lightly with a hammer in that general location about 2" - 3" away from the edge of the casing and about 48" - 54" off the floor. If you hear a different sound that just might be it. Before you start pounding on the wall make certain by hammering a screwdriver into the wall and if you hit the box it will stop the screwdriver from going any further and you should hear metal to metal sound. At that point you break out the patching and you'll find two black wires. At that point you have the two wires you'll need to wire up a single pole switch.

As far as aluminum wiring the only way I've seen aluminum is in Romex type form. As far as I know I have never seen either a #12 or #14 aluminum single wire in a house for knob and tube. Knob and tube wiring was always soldered where they made there splices so it had to be copper wire to be able to solder the wire together. If you or anyone else that reads this and you know you have aluminum wiring you should have an electrician look at your main panel and any sub panels. You should have him tighten the screws in the breaker clamps that the wires are attached to. Over time the aluminum does break down slightly just enough to where the wires might not be attached as tight as they should be. Sometimes loose wires can start aching and the wire ends can get quite hot, which could create a lot of heat which is not a good thing.