I have an old house and am replacing a dimmer switch in the kitchen.The old switch is has only 2 wires coming out of the switch that are both black. From the wall 2 wires connect to the 2 black wires on the switch, one is black which I have concluded is hot and the other is red, which must be the common wire. My question is that there is a 3rd wired that is pushed into the electrical box that is capped and not being used. This wire is white. I can only assume that would be a ground wire, but why would it be white in color. Can you tell me what the coloring scheme was for wiring old houses? Now I can connect the switch and use only the black and red wire, but would like to ground it properly if possible.
This Site Might Help You. RE: what do wire colors mean (old house)? I have an old house and am replacing a dimmer switch in the kitchen. The old switch is has only 2 wires coming out of the switch that are both black. From the wall 2 wires connect to the 2 black wires on the switch, one is black which I have concluded is hot and the other is red, which must be...
These would be normally. You should have them checked before you connect something. Black is hot White Neutral Red wires are also used for hot wires, switch legs (like to a ceiling fan), and are the second hot wire in 220-volt installations. Another useful application is the interconnect wire between two hardwired smoke detectors. A ground would be green or bare.
Since this is an old house I would not assume anything, I may hook up a new switch wire per wire, but unless I opened the light fixture and confirmed the connection I would not connect any unconnected wire. That being said, since you have two colored wires then the white should only be used as a neutral. The hot and switch leg back to the light should be black and red, but which is which is anybodies guess. A ground wire is probably not present in the j-box you are dealing with, it was not required for many years, and probably do not have any grounded connection point in the light j-box either. You would just be connecting the boxes together if you used this spare wire, but not actually grounding anything, and could create a larger hazard by doing so.
To begin with, don't worry about the white wires tied together in the back of the switch box, that's normal to see in a switch box (outlet boxes are a whole different ball game). The only purpose of a switch (regular or dimmer) is to control the hot (black) side of the circuit that powers the light (or fan or whatever it is). To simplify this for you, just connect one black wire from the switch to the black wire in the box and the other black wire from the switch to the red wire in the box. That will make the connection and your light will work on the dimmer. If there is a green wire on the dimmer switch, connect that to the bare copper wire inside the box. If no green wire, then just screwing the switch to the box will ground it assuming it's a metal box. The metal box should already be properly grounded, you might see a bare copper wire screwed around a terminal inside the box. If the white wire is by itself (or tied in with other white wires) with a wire nut (cap) on it, don't worry about it and don't let it confuse you, it's just an extra wire that's not needed for the switch to work. The only case of where you'll see a white wire connected to a switch is if 14-2 wire was used instead of 14-3 wire (like in your case). 14-2 has a black, white, and bare copper wire. 14-3 has a black, red, white, and bare copper wire. The 14 just means the gauge (thickness) of the wire. And to confuse you even more, another case of seeing a red wire connected to a switch is if the circuit is a 3-way circuit whereas there are 2 or more switches controlling the same light. In your case though, I'm assuming this dimmer switch is the *only* switch controlling your light given your description. Keep in mind, YouTube is a great source for tutorials on doing electrical work if you need it. Just remember to kill the power to the circuit you're working on. Anyway, hope this helps, and good luck.
