Electrical Basics ~ Residential Wiring Diagrams

Wiring Diagrams ~ The Four Way Switch...

In a four way situation, the power and switch leg are typically wired at the three ways. The difference is the additional switch. The four simply acts as a switchable interchange, between the 2 sets of travelers.

A four way switch will come with 4 poles, grouped in pairs. Usually 1 pair will be brass and the other will be black. To wire the four way, connect the red and black wires, from each 3 wire cable, to either the pair of brass or black screws on the switch.

Then wire the three ways and fixture as usual.

Wiring Diagrams ~ The 2-Wire Switch Loop...

The "switch loop" can often be found in older homes, with "knob and tube" type wiring. Where power is fed through the lights and back fed, down to the switch, using a 2-wire set up or cable. This is possible, since you do not need a neutral wire, down at the switch, to make it work. You are only switching the "hot" conductor.

To wire the switch loop, you will connect the white wire of the switch leg, to the black/hot wire that feeds power into the light box. Then connect the black/hot wire of the switch leg to the black wire at the fixture. The source neutral/white wire, will connect directly to the white wire at the fixture.

You'll need to re identify the white wire, of the switch leg, that was used to send power down to the switch. This will identify the conductor as being a hot wire and not a neutral. Do this, at both ends of the wire, using either black tape or black marker.

NOTE: The 2011 Edition of the NEC has required that a "neutral" wire be present at every box. This is done to keep folks from using the ground/bare wire as a neutral, say to add a outlet under a switch. The area you live in, may or may not have adopted this requirement or the 2011 NEC. Each jurisdiction is different.

If you are wiring a new installation, you'd be advised to follow this code.

Here is a switch loop, wired to meet this new requirement in the NEC.

Everything is as you'd find in a 2-wire switch loop. However to meet the code, you'll need to run the third conductor for the neutral. This can be accomplished by using a 3 wire NMB as shown above. Simply cap off the unused neutral in the switch box, with a wire nut.