I am confused something. I want to install a tankless water heater. Mounting the device, the plumbing, wiring, routing to the 200amp panel is all easy and straight forward.
Where I get stumped is the two breakers.
75A (2×40)A 240 8 AWG
The directions show to run 2 8/2 with ground.
The Illustrations show to connect both black(hot) and white(N) to the two prongs on the breaker.
I totally get 240v using a black red and white. but 240 connecting the Neutral to a hot I do not get.
I guessing something like a dryer really is has two components using 120v each sharing a nuetral and we call it a 240v.
But true 240v is doubling up on the hot but what about the neutral?
If anyone can explain this I'd appreciate it.
UPDATE
Thanks for all the comments but seriously guys, getting all hung up on the "White is just a color" is odd.
I know a white wire is a wire.
So when you connect a wire to the hot and another wire to the neutral (in this case they are (pink and blue) on the panel. Then connect the other ends of these 2 wires to a 120v outlet. The current being AC travels in alternating directions on this pair of wires.
So if I instead connect both of these wires to hot and connect the other ends to lets say one of the heating chambers of a tankless water heater. I got lost on how the alternating current occurs the same on 2 hots rather that a hot and a neutral.
That my question. I am not asking how the current knows it's on a pink wire.
Best Answer
Confusion from failure to use marking tape
Yeah, I know. Marking wires with electrical tape to indicate function seems like such a needless chore. "I only need to understand it right now. I will never be in here later troubleshooting!" This of course ends up not working 1/4 as well as expected. Some of the people who are marking-hostile write installation instructions.
Since UL approves installation instructions, I'm surprised they don't make the instructions follow Code. Because in this case, Code sides with me.
It is illegal to use white as a hot.
However, if you are buying pre-manufactured cable, what you are allowed to do is use paint, tape, shrink tubing, etc. to re-color a white wire to be an appropriate hot color.
But it's mandatory.
So the most straightforward answer is to take your #8 supply cables, and after you're done stripping off the cable sheath to fit, go ahead and wrap the white wire with red electrical tape.
You can also use black, since there's no particular need with a water heater to match up phases. A 240V circuit with black-black hot wires is perfectly fine.
If it were in conduit, that would be a different deal. Because individual wires are easy to swap, you're required to use the correct color in the first place - no remarking is allowed.
If you're absolutely militant about refusing to mark wires, then my only advice is to use /3+gnd cable (black red white) and just cap off neutral. That would allow you to use one of the cables for a subpanel if the tankless heater doesn't work out.