While doing electrical wiring in your home, you’ll likely encounter a junction box with wires that need to be connected with wire connectors. These plastic connectors, often called wire nuts, twist over the wires to make a tight connection around the wires. Better wire connectors have a square-cut spring inside that provides tension on the wires to hold them secure. As you tighten the wire connector, the spring draws tighter around the wires.
By stripping two or more wires about 1/2 to 3/4″ and lining up the ends, you can twist the wire connector over the wires. Although this connection is considered a good connection, I advise to twist the wires with lineman pliers in a clockwise direction before applying the wire connector. It makes for a better and more secure connection in my opinion. The main advantage with this connection is in areas where vibration may loosen the wire connector and the wires could come apart.
Wire connectors come in different colors. The color indicates the size of the wire that they are capable of holding secure. The following chart will help explain what color wire connector is capable of holding what size wire.