I thought using the conduit as ground was no longer allowed.

Nope still ok as long as it’s one of the metal conduits. Older armored cable (BX) is right out.

Red, white, and blue sounds all American to me.

So, Ron, why did the electrician who inspected the wiring of my old home, which was wired with EMT, said that I had to run a green ground wire through all the conduit? It was quite difficult to do this (had to pull the old wires out, add the green wire, then pull them all back!).

Either your electrician was wrong (all electricians are not created equal) or there was some kind of special circumstance that called for it.

I'm not a code junky, but I googled and found this section from the 2014 NEC:

Article 358 Electrical Metallic Tubing: Type EMT

358.60 Grounding. Grounding and bonding EMT shall be installed in accordance with 358.60(A) and (B).

(A) EMT shall be permitted as an equipment grounding conductor

(B) Where Air Conditioning or Refrigerating Equipment is installed outdoors, an equipment grounding conductor per 250.118(1) shall be provided within the raceway and shall be sized per 250.122.

OK, thanks, Ron.

I dont like the amount of space for those wires.

A surface box would be more appropriate. Is the wall hollow so it can accomodate a normal sized box or is it concrete behind the plaster?

Mike. So if you are wiring in a Lutron Maestro dimmer, that has a black, red, red/white, and green wire in the back, how would you wire it? What I did for now and it is working is as follows. I basically copied what the other switches has. I connected the red wire from my conduit to. The black wire of the new Maestro. I connected both blue wires together as it had been done on the old switch and connected them to the red wire on the Maestro. I capped off the red/white wire. I capped off the ground. All the other switches in the home are not connected to the white wires, nor are any grounded anywhere. The cover plate for the light switch is completely plastic and screw less cover. Please let me know what you think.

What model of the Lutron Maestro dimmer do you have? The instructions should show how it should be wired and if you give us the model number, we could look it up.

One error is that you shouldn't just cap off the ground. It should be connected to the box (which is presumably grounded). You may need to get a self tapping ground screw to make a proper attachment to the box.

Hi Greg, thanks, will mention that Friday to the electrician. I was mistaken, not Maestro, was the diva.

https://www.homedepot.com/p/Lutron-Diva-C-L-Dimmer-for-Dimmable-LED-Halogen-and-Incandescent-Bulbs-Single-Pole-or-3-Way-White-DVCL-153PR-WH/203670402

Okay, so it's a dimmer that doesn't require a neutral (some do). So what you did is fine other than the ground wire.

OK good. I was worried about pairing the blue wires together. Also the light worked with the blue wires on the black wire if the switch as well.

Again right now, I have the 2 blue wires attached to the single solid red on the lutron. I have the red wire attached to the black of the lutron. That is safe? I will turn off power and add the ground later today.

Yep. With this switch, it doesn't matter which way you attach the wires to the switch.

Regarding the blue wires, the situation there is that one of them is the incoming power. It is attached to another blue which feeds the constant power downstream to some other device AND it's attached to the switch which feeds power (ON/OFF) to the red wire that travels to your light.

Actually, re-reading your description, the blue wire (that isn't the incoming power) travels with the red to your light and then isn't used there. So you have switched power and constant power (that isn't being used) at your light box.

Or does the blue wire continue from your light box to somewhere else? Maybe it is being used somewhere downstream.

Maybe, not sure. But I am happy it is safe as is. I will still have the electrician out to examine it. All the light switches in my house have the same two blue wires wired together if that helps.

I re-read again (I really need to learn to read closer) and it looks like you said the blue that was the incoming hot is in the same conduit as the red.

If that's the case, then I described it a little backwards. I was picturing the other blue as the power source.

(Everything is still safe and proper, it's just my description of where the power is travelling is a little off)

So the situation is that the power comes into your light box first (but isn't connected to the light at that point), then it travels to the switch on the blue wire at which point the red returns the switched power to your light (this is called a switch loop if you'd like to google it for more info).

The power also continues on downstream in the other conduit to somewhere else.

Thanks for the explanation. Resolves some anxiety for the week until the electrician makes it out to look it over. Should I be grounding every switch in my home. I have checked about 15 switches and outlets now, none are grounded. They are all in metal boxes and have plastic covers. I have read that as long as there is a plastic cover, no ground is needed?

I'm no expert on grounding.

I'm in Canada and on 'normal' switches, we don't even have ground screws so I'm guessing it's not that important. Dimmers and timers and whatnot have ground wires, so I always attach those to the boxes and ground wires in the wall.

With duplex receptacles, you're required to run a wire to ground them to the box and the ground wires. I think there are 'self grounding' receptacles but they aren't the norm.

But then again, having all of your wiring in conduit is not the norm either, so maybe you have self grounding receptacles.

But it never hurts to explicitly ground something. So I'd definitely do it for this dimmer.

As far as doing it to the rest, just wait and ask your electrician's opinion.

I'm trying to figure out what I'm seeing in the photo above. Vith mentioned wire space, and at first glance it does kind of look like a square version of a pancake box.

But after looking at it a while longer, I think maybe we're seeing a plaster ring, and there's a much larger box behind it, inside the wall.
Otherwise, I can't imagine how a switch, let alone a dimmer, could fit into what appears to be a really shallow box.

It's a normal sized box, it is wider behind the drywall and deep enough for the large lutron dimmers to fit in. No plaster either, it's studs with drywall.

So, Ron, why did the electrician who inspected the wiring of my old
home, which was wired with EMT, said that I had to run a green ground
wire through all the conduit?

Good question. With few exceptions EMT functions as the grounding conductor. Adding an actual wire would be "belt and suspenders" but in any case I would imagine it would have to be sized for the largest conductor and it would have to be connected to each box and/or device. Years ago I did see a home where the foundation had started to collapse and when the problem was fixed, the pulled apart a run of EMT. There was enough slack in the run that the wires stayed connected but the ground was lost.

But after looking at it a while longer, I think maybe we're seeing a
plaster ring, and there's a much larger box behind it, inside the wall.

In my experience it's pretty common to use a 4" square box and a mud ring. That typically provides plenty of space and about 2" of depth.

I think there are 'self grounding' receptacles but they aren't the norm.

There are self-grounding devices that will either have a little brass tab or a pair of wires on the yolk that "captures" one of the mounting screws. Those devices are typically more expensive. Otherwise ground the device with a short piece of wire. That wire should be attached to the box with a threaded screw (not sheet metal). One of the holes in the back of the box will be threaded to accept those cute little green screws sold in the home center.

So if you are wiring in a Lutron Maestro dimmer, that has a black, red,
red/white, and green wire in the back, how would you wire it?

The two blue wires coming in from the top left and top right get attached to the black wire, red to red, ground to the box as discussed in the previous paragraph. Red striped gets capped off.

OK, that makes sense. Thanks.

BTW, it's still called a plaster ring, even when it's installed in drywall.

Will it be a problem with the blue wires attached to the red and the red attached to the black? Just curious as it's functioning well.

I believe code allows any wire not white, grey, or green to be hot. I did some wiring in a condo I owned in Chicago and all the hot wires were orange!

Hi Mike, can anything happen with the blue on the red and red on the black?

Of course, you have to know where these wires go. Having them different colors helps, but it still may take some effort to figure this out. What kind of residence is this - single family house with basement, multi story condominium, etc.? Also, what age?

Single family, built in the 60's

There's nothing magical about the colors. Anything not white, grey, or green can be hot. Connecting different colors might confuse the next guy who works on the circuit, but it won't harm anything, as long as you're sure you know where the wires go and that it's connected correctly.

David, so connecting the hot blue wire to the red instead of the black on the lutron diva light switch is ok? I just want to be sure, my electrician is not coming out now until Monday as he is doing a rewire job which is taking him longer.

Sorry, I don't know anything about Diva dimmers. That said, the instruction sheet you posted above (though it's only the illustration) seems to be saying (since the wires in the box aren't labeled as source or load) that it doesn't matter which wire goes to source and which to load.

If I'm wrong about that and the dimmer instructions DO say that the power source should be connected to one of its wires (red??), and the load to the other (black??), then that's the way you do it, regardless of the colors of the wires in the box.

You determine which box wire is which by reliable means (voltage tester, multimeter, etc), and not by assuming the colors mean anything in particular.

As the semanticists say, the map is not the territory.

Or, as my driver's ed instructor said many many many years ago, that yellow light blinking on the car coming at you in the other lane means that there's a light blinking on the car in the other lane. That's all. It tells you nothing about what the other driver is going to do. All that matters is what he actually does.

And here all that matters is what the wire actually does, not its color.

Besides, if you do mess up, what's the worst that can happen? The light doesn't work, or (unlikely) you wreck the dimmer. Inconvenient and annoying maybe, but not a major disaster.