Why doesnt 240v need a neutral? #electrician #nationalelectricalcode

追加: 2026-05-23

[00:00:01]Okay, how does 240 volts work if there's no neutral? That's basically what the commenter is asking is we are taught that the hot wire is the supply and the neutral is the return and then when you have 240 volts you appear to have two supplies with no return and that seems to confuse some people. The answer is simple. We have AC, everything goes back and forth whether it's 120 volts or 240 volts. So, if this is one hot, this is another hot and this is your neutral.

[00:00:25]A 120 volt circuit will indeed flow this way into the neutral 50% of the time and then as the sine wave reverses, it flows that way from neutral to hot. So, hot to neutral then neutral to hot. So, when you upgrade to 240 volts, the only difference is instead of using half the winding of the transformer, you're using the entire winding but the physics is the same. 50% of the time, the current flows from one leg to the other leg so from one hot to the other hot and then the current reverses and flows the other direction from one hot to the other hot.

[00:00:56]Each hot takes its turn being supply and then return back and forth for each other. Now, a lot of people have trouble believing that but I have a demonstration that will show us an effect caused by that. So, let's get into it.

[00:01:09]Okay, here's the setup. From this panel, I've run two hots and a ground through that cable. No neutral.

[00:01:16]Just a 240 volt circuit, two hots and a ground. And the only thing I have connected to this load is the two hots and they're boiling water.

[00:01:26]So, what I'm claiming is the current flows out of this hot through the hot plate and then back into this hot and that's its return path to the transformer. And then the sine wave cycles and the current reverses direction. Now, it does that super fast but that is what it's doing.

[00:01:43]Okay, if you don't believe me, I have a demonstration that will show an effect caused by that back and forth.

[00:01:48]I use some diodes and some light bulbs.

[00:01:51]Here's the DC version I built that I might show in a different video that kind of explains what's going on at a slower pace.

[00:01:56]But let's look at the full speed version first.

[00:02:00]Before you go to the next step, give me 10 seconds to thank Jonard Tools. I just went to New York City with Jonard Tools, and they took us on a tour. There were a bunch of other content creators there, and they were all smart enough to take enough videos that they can come back and make a montage of all the fun we had. I was not that smart. I always forget to do that when I'm at these events. So, instead of making that montage, I'm going to thank them in the middle of this video. So, thank you very much, Jonard Tools. I had a blast. All right, back to the video.

[00:02:25]Okay, the final setup will have two light bulbs, but this is the first light bulb. I've created the yellow path.

[00:02:30]Current's going to flow from here, through that diode, through that light bulb, and back into that hot. This diode will block current from flowing in this direction. It only allows current flowing in that direction. So, this will only get power when the current's flowing that way.

[00:02:46]Okay, there's light bulb number one.

[00:02:48]All right, so now I've added the second light bulb, and this is what we're going to call the white path. Can you follow the white path? It flows from the black, through that diode, through the light bulb, and then back to the red. But, it because the diode's in place, current cannot flow the opposite direction. So, if current is indeed reversing directions, only one light bulb should light at a time.

[00:03:08]Okay, let's energize the setup.

[00:03:11]Take a look.

[00:03:13]Are they blinking?

[00:03:14]Yes, they are blinking. They're just blinking too fast for our brain to register. So, let's look at them in super slow motion.

[00:03:21]That looks like an alternating blinking pattern to me.

[00:03:24]All right, moving on.

[00:03:26]Okay, same demonstration with LED bulbs.

[00:03:30]Let's see what they look like in slow motion.

[00:03:33]Okay, more blinking lights.

[00:03:35]Here we go.

[00:03:38]So, I think it's a better effect with the LED than it is with the incandescent, but they're called LEDs cuz they're called light emitting diodes. So, adding a two more diodes to my setup kind of maybe somebody in the comment section that knows more about electronics would say why this invalidates the result.

[00:03:54]The incandescent is indisputable. That to me that shows current reversing direction.

[00:03:58]But I say indisputable, but every time I show this effect in a video, I still get a bunch of people telling me what I misunderstood or why I was wrong.

[00:04:05]So, what do you think?

[00:04:06]All right, thank you very much.