Help with wiring a NEMA 10-30P outlet!

[coulomb]

^^ My electrician put red tape on the white wire he used for the second 'hot' connection.

Ah, so it's true! And tape, no less, which always seems to lose its stickiness after a few years. Excuse me while I adjust to the new (to me) reality... wow. What a weird world.

A yellow stripe is a good idea. I don't think I have noticed it on my wires.

It's one of those international standards. In my country, "international" has favourable connotations: standardization, the good of the world, working together towards a common goal, that sort of thing. I get the feeling that in the USA, not so much. My apologies if that's unkind or simply mistaken.

[SageBrush]

^^ My electrician put red tape on the white wire he used for the second 'hot' connection.

Ah, so it's true! And tape, no less, which always seems to lose its stickiness after a few years. Excuse me while I adjust to the new (to me) reality... wow. What a weird world.

A yellow stripe is a good idea. I don't think I have noticed it on my wires.

It's one of those international standards. In my country, "international" has favourable connotations: standardization, the good of the world, working together towards a common goal, that sort of thing. I get the feeling that in the USA, not so much. My apologies if that's unkind or simply mistaken.

.
I'd say that the local message is "don't rely on the wire color."

[jjeff]

Sage is correct, it's done somewhat regularly if they are repurposing a white wire(for example going from a 120v circuit that used the white wire to a strictly 240v circuit that needs another hot but no white/neutral). They use a quality(generally 3M) colored tape(electricians always carry a supply of colored tape on their cart) and wrap it several times around the white insulation on both ends near the connections. Wrapped several times it's not going to come off even if the tape loses its stickiness and you NEED to know this white wire is a home run(not shared by any other circuits or spliced in a box anywhere between the panel and outlet. I'm pretty sure but not positive a green wire cannot be repurposed, it always needs to be ground. Not sure if say a black wire can be repurposed to a white wire, I'm sure a real electrician will know.
Now what I've occasionally done besides using the tape is to use a red or black sharpie type of permanent marker to also color the white wire the correct color, figure it can't hurt and anything to draw attention that the wire is no longer a neutral. I kind of agree that the neutral should have been black or the color of our negative wire in DC circuits but maybe they wanted to differentiate between AC and DC where in DC ground is black and hot red. As mentioned our AC uses white for neutral, generally black hot and often red for the second hot but can also be used in 120v circuits and lots of other colors(yellow, orange, etc.) for other hots.

[Nubo]

BTW, is it true that you actually have pure green ground wires in places? The extra cost of the yellow stripe to pander to color blind people is outrageous?

Either green or bare Copper. The Earth still manages to wobble about its axis, somehow.

[LeftieBiker]

Last year I was watching an ep of This Old House, in which an electrician installed a charging station for an EV. He used a white wire as the second Hot, and didn't bother to re-label it. That's "felony stupid" in my book.

[Oilpan4]

I have only seen a hand full of correctly installed dryer circuits over the last 15 years.
Usually the only ones wired correctly are the 4 prong, 4 wire 14-30 outlets.
I don't think I have even seen a properly marked 2 insulated wire (black/white) with a bare ground wire romex or triplex cable used on a 240v circuit properly marked unless I put it there.

[goldbrick]

I don't think I have even seen a properly marked 2 insulated wire (black/white) with a bare ground wire romex or triplex cable used on a 240v circuit properly marked unless I put it there.

Ditto for me. I have to confess though...even when I've re-wired some of my own 240V circuits I didn't bother to mark the white wire as a hot. It's my house and it's obvious that the outlet and breaker are 240V so it is hard to forget that it's a 'hot' wire.

As for the US NEC rules for wire colors, my understanding is as follows:

For wire sizes <= 6 AWG

ground wires are green or bare copper. Green colored wires cannot be remarked for any other use, regardless of size.
neutral wires are white or gray, or a base color with 3 continuous white stripes
any other color (not green, white or gray) is a hot wire

For wire sizes 4 AWG and larger, wires that aren't green or white can be remarked since as Henry Ford said, you can get this size wire in any color you want as long as it is black.

[Oilpan4]

Watch out for gray wires.
The only time I have encountered them is where multiple circuits share a neutral.
They are a pain to completely deenergize.
So you turn it off, unwired the neutral, it sparks as it disconnects and lights some where else go out.
Now you have a live energized neutral to work around.

[LeftieBiker]

I have to confess though...even when I've re-wired some of my own 240V circuits I didn't bother to mark the white wire as a hot. It's my house and it's obvious that the outlet and breaker are 240V so it is hard to forget that it's a 'hot' wire.

Houses get sold or passed down to kids.

[goldbrick]

Houses get passed down but more importantly, people live in them. I would never do anything half-a$$ when it comes to wiring a house and I don't condone anyone else doing it either. However, I'd guess that 99% of the 240V household circuits that use romex (NM-B) cable for the 240V circuits use black and white wires for the 2 hots and the white wire is not re-marked with another color. I just passed an electrical inspection on some work I did on my house and that point was never mentioned, even though I did the exact same thing. This wiring method is common to the point of being a de facto standard although technically, I think it does not meet code. There may be an exception in the code for this situation that I'm not aware of but my understanding is that the white wire of a 240V circuit should be re-identified with tape or other marking to indicate it is an ungrounded conductor. But virtually no one (except Oilpan) does that.