The old method of a 2 wire drop is explained along with the current code requirements of using a 3 wire cable. If you put the loop over the screw in the counterclockwise direction tightening the screw will force the loop open and could create a loose connection.

2 Way Switch Wiring Diagram Light Wiring
What is a switch loop in wiring. The 2011 nec code requires that the switch loop use wires of the proper color code to signify hot wires. Wiring a switch loop. In a switch loop this is not how its done. In a switch loop the hot and neutral wires arrive at the light fixture before reaching the switch. Wrapping the wire clockwise when wiring a light switch ensures that the loop on the end of the wire will tend to close when the screw is tightened. A white wire signifies a neutral wire.
Wiring a 3 way light switch. How does electrical switch wiring work. When the electrical source originates at a light fixture and is controlled from a remote location a switch loop is used. Switch loops work by stealing a hot thats in an attic or maybe in a light fixture box in the ceiling and sending that hot down to the switch on a. Loop in lighting wiring is the modern cabling arrangements used in most installation. A switch loop occurs when both the switch at the end of a circuit or an incoming cable and a neutral become hot leads and connect to a terminal.
This circuit is wired with a 2 wire cable running from the light to the switch location. With a pair of 3 way switches either can make or break the connection that completes the circuit to the light. Figure 2 diagram of a switch loop. For new wiring you would run a three wire cable and use the red and black for the loop and leave the white unused and capped in the switch box. The tab connecting the hot terminals on the receptacle is removed and the source hot is connected to the bottom half. Bib jun 1 15 at 1238 1 if you are working on an older home with unmarked switch loops when you trace them also mark the white wires that should be marked so that they are marked for the next.
Wiring a 3 way light switch is certainly more complicated than that of the more common single pole switch but you can figure it out if you follow our 3 way switch wiring diagram. The source neutral is connected to one of the neutral terminals on the receptacle. The neutral from the source is connected directly to the neutral terminal on the light and the source hot is. This diagram illustrates the wiring for a split half outlet controlled with a switch loop. Wiring a split switched outlet with a switch loop. Generally it uses less materials and is quicker to install than radial junction box wiring it can however be a bit more complicated to work out the actual wires at a ceiling rose.
This shows wiring a light switch when the power comes into the light outlet first. From a physical wiring standpoint it will be necessary at a minimum to run 143 cable which contains a black red and white wire.