What does knob and tube look like with the walls removed?

Look at your wiring behind the wall and you will see all sorts of cheats

This is knob and tube wiring in a room where the plaster ceiling has been removed. Here you can see new wiring that is connected to the old knob and tube wiring in a flying splice. This is a common cheat that handymen do to save time and money. It is dangerous because it can over load the old system; it is also missing a junction box so when the connection fails spark can cause a fire.

Here is properly installed knob and tube as it was originally installed. It is in good shape but it is still far below today standards.  If it were in bad shape the cloth isolation would be falling off exposing the live copper wire inside.  You know this is original because the old boxed were designed to attach directly to the wood lath and installed before the plaster.

Here is an example of a BX wire cheated into an old knob and tube box. The problem here is extending the old wires past what they are designed for. The BX is also not terminated correctly. The metal jack if free to cut into the cloth covered wires. In a correct installation the metal BX would be connected to the box.

Here is another flying splice for a ceiling fan that was added to the old lighting circuit. Again this is the work of a handyman cheating the system. It is much less costly to do work this way but is not worth the added risk of a poor installation. The fan is clearly working and with the ceiling installed the homeowner would not know there was even a problem until something went wrong.

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