How to wire light with a switch in the middle of a circuit

Question

I am attempting to reinstall a switch in a room in my house. Within the box there are two cables. The cable on the left has a black and white wire. The cable on the right has three wires a black, a white, and a red wire. The way it is currently hooked up is that the red wire is pigtailed off, the white wires are pigtailed together and the black wires are connected to either ends of a single pole switch.

The problem is that this configuration results in the switch controlling both the lights and the outlets in the room. So when the switch is turned off it would remove power to the outlets as well as the overhead light.

After doing a bit or research I think I have a light switch in the middle of a circuit. I think it is probably like the wiring diagram in the following link "Power at switch diagram".

http://www.easy-do-it-yourself-home-improvements.com/light-switch-wiring-diagram.html#switch1

What would be the correct way of installing this switch? Are there any suggestions for how I can figure out how the circuit is connected in my house?

Answer 1

It depends on which side of the switch is the line (power source from the box) and which side is the load (light and outlets).

If the two wire cable is the line and the three wire is the load, you may be able to use the red wire to carry uninterupted power to the outlets. The next question is whether the light or the outlets come next in the circuit, and whether that red wire shows up in their respective boxes.

If the outlet is next and the red wire is also capped in that box, you can use the red to power the outlets while still switching the light. Connect the incoming black line wire, the exiting red wire and add a black pigtail (a short length of wire). Then connect the other end of the pigtail to the switch where the incoming black wire was previousl.

At the outlet box, remove the incoming black wire going to the outlet and replace it with the incoming red wire. Attach the incoming black wire (that is now free) to the black wire going to the light. This may be attached to the far side of the outlet. If so, disconnect it from the outlet first.

If the light is next in line, this will only work if there are both black and red red wires going to the light fixture box. In that case, remove the outgoing black wire (going from the light to the distant outlets) and attach that outgoing black to the incoming red. Leave the incoming black on the light fixture.

If the red wire does not show up in the next connection box, you are out of luck unless you add additional wiring.

In sum, you need two hot wires leaving the switch box, a black one that is switched and a red one that is always hot. You are trying to keep the switched black connected to the light fixture and the unswitched red powering the outlet. (The colors are arbitrary, but since the red is not currently in use, we have designated it always hot).