What are these wires?

[SimpleCycle]

I am trying to rewire a dimmer switch to a single pole light switch.  I opened up the switch and found this:



That's one yellow wire, two blue wires, and two white wires.  The yellow and blue are connected to the dimmer switch and the white are just wired to each other.  I am fairly certain the yellow is the hot wire.  Can someone help me identify the rest?  Is there no ground wire?  Is that a problem?

[paddedhat]

Due to pressure from trade unions, you live in one of the few areas in the free world where residential wiring is still done with metal conduit and individual wires pulled through the conduit system.  As a result , in the other 99% of the US, Romex cable is the standard for wiring homes, and has been for the better part of a century. This leads to a "standard" of sorts, in which there are only three common colors in 120V residential Romex installations. They are white for neutral wires, and black and red for hot wires. Grounds are almost always bare copper. Once you are using individual wires in conduit, however, the rules change.  Simply, white and gray are neutrals, greens are grounds, and any other color can be a hot wire. My guess is that your yellow is a spare wire intended to serve a ceiling fan/light combination to allow the fan and the light to be controlled separately. It doesn't mean that there is a ceiling fan installed now, just that the system was installed to allow future installation. While wiring new homes, I do this to all bedrooms, dining room, etc, but use Romex with an extra red wire to accomplish the same thing. The white(neutral) wires are nutted together in the box because they are passing through to the fixture and not required at the switch box. The lack of a ground is not best practice, but legal, since the entire system is installed in metal conduit, and the code considers the entire conduit system to be a ground.

[ncornilsen]

....The lack of a ground is not best practice, but legal, since the entire system is installed in metal conduit, and the code considers the entire conduit system to be a ground.

And that right there has burned more houses down than Romex has, by at least an order of magnitude.

[paddedhat]

....The lack of a ground is not best practice, but legal, since the entire system is installed in metal conduit, and the code considers the entire conduit system to be a ground.

And that right there has burned more houses down than Romex has, by at least an order of magnitude.

Quite possibly. The funniest part of the whole Chicago conduit scam is that I have had argument, more than once, with a   tradesmen from that part of the country, who claims that they would never live in a house wired in Romex, since it's inferior and dangerous. Once I make it clear that they are full of shit, they default to "well, conduit is way better, since it's easier to add a circuit". I wholeheartedly agree with this statement, assuming they are referring to a concrete block or poured concrete wall house. If it's plain old stick framing, any competent electrician, with the right tools can get a new Romex circuit where it needs to be, with no problem. I've been licensed since 1988 and can say that of the countless miles of wire I've pulled in conduits from 1/2" to 5" sized, I've never pulled a run without a ground.

Another major issue in residential grounding is water pipe grounds. The service is bonded to the water pipe, the pipe is grounded via. direct earth contact as it leaves the building underground. Until some part of the system, underground or in the home, gets replaced with plastic. Shortly before I bought my current home, the owner and his "plumber" buddy repiped the supply lines with CPVC. They removed the ground clamp from the old pipe and pushed it off to the side, leaving the entire house ungrounded, until I drove rods outside and regrounded it. I've heard of homeowners losing entire homes full of appliances and electronics after a nearby lightning strike, since they didn't know the house was ungrounded after the water line in their yard was replaced. 

[SimpleCycle]

@paddedhat, thank you so much for the thorough explanation.  There actually IS a ceiling fan there, but for whatever reason both the fan and the light were wired to a single dimmer, which is why I was rewiring.  I'd actually prefer the fan and switch be wired separately, which would mean installing a double box and sorting out which wire goes to what.

As it was, the yellow was wired to one of the dimmer wires and the two blues were wired to the other wire.  Based on that I wired the yellow wire to the top of the switch and the two blue wires to the bottom of the switch.  If I were to separate the fan from the light, how would I rewire?  I'm looking at wiring diagrams and can't quite get it.

[SimpleCycle]

Oh, I think I have it.

The yellow is the line and the two blues go to the fan and the light.  I split the yellow to each switch, then run one blue to the light and one blue to the fan.

[paddedhat]

sounds like you got it. I screwed up and thought I read that your yellow was just capped off.  If you are adding another switch it should be a pretty easy deal. The box in the wall is 4" square. You need to cut the sheetrock until you have the outside edge of the box exposed. Now unscrew the single gang ring, and go get a double gang one. They are on the shelf at the big box stores. You need to match the ring depth, typically 1/2" or 5/8". you will have an unusually large hole to cover up, but an oversized (often called jumbo) double gang switch plate should hide everything.

[SimpleCycle]

Okay, I pulled down the ceiling fan today and am still confused.

In the switch box: two blue wires attached to the bottom of the switch, one yellow wire attached to the top of the switch, two white (neutral) wires nutted together.

In the ceiling box: one yellow wire attached to both the fan and light wires, two white (neutral) wires attached to the neutral wire for the fan, two blue wires nutted together in the ceiling box running to nothing.

Do the two wires mean there's something further down the circuit?  Nothing else is operated by the fan/light switch.

[zolotiyeruki]

@paddedhat is welcome to correct me if I've got something wrong, but it sounds like:

Blue wire in switch box: always-on line voltage coming from your panel.
Yellow wire in switch box: power from the dimmer up to your ceiling box.

Blue wire in ceiling box:  always-on line voltage coming from the switch box, and continuing on somewhere else (likely an outlet on the other side of the room). It is not affected by the switch.
Yellow wire in ceiling box: comes from (and is affected by) switch/dimmer.

Typically, ceiling fans with light kits will have two hot connections, one for the light and one for the fan.  In your case, you would normally connect the fan wire to the blue wires (so that you can turn the fan on with a pull chain, independent of the light), and connect the light wire to the yellow, so you can switch the lights on with a light switch or dimmer without affecting the fan.

[SimpleCycle]

@paddedhat is welcome to correct me if I've got something wrong, but it sounds like:

Blue wire in switch box: always-on line voltage coming from your panel.
Yellow wire in switch box: power from the dimmer up to your ceiling box.

Blue wire in ceiling box:  always-on line voltage coming from the switch box, and continuing on somewhere else (likely an outlet on the other side of the room). It is not affected by the switch.
Yellow wire in ceiling box: comes from (and is affected by) switch/dimmer.

Typically, ceiling fans with light kits will have two hot connections, one for the light and one for the fan.  In your case, you would normally connect the fan wire to the blue wires (so that you can turn the fan on with a pull chain, independent of the light), and connect the light wire to the yellow, so you can switch the lights on with a light switch or dimmer without affecting the fan.

Yeah, I think you are totally right.  It actually was connected with both the fan and light wired to the switch and the blue wires running through the ceiling box to whatever they are powering later down the circuit.  It's nice to know I can do it a way that puts just the light on the switch.  Thanks!