﻿Welcome to another episode of CircuitBread Practicals where we talk about the intersection
between electrical work and electrical engineering and trying to make it so as electrical engineers
we aren't quite so embarrassing ourselves when somebody asks us to do any sort of work or at
least give some advice on what's going on an electrical system in a house. So today,
we are going to talk about how to wire up a 240 volt circuit.
Now, this is really really simple and not that common but I thought it'd be good to go over.
So most of the time when you're working in any residential or commercial applications you have
your outlets, you have your lights, everything, everything works at 120, at least here in the
United States. But every once in a while you get a 240 volt piece of equipment that's necessary,
either that's a really large power supply in your lab or it's a piece of woodworking equipment or
it's your air conditioner condenser or your hot water heater, something like that.
So what you do is you have your panel and this is the panel that we have in our shed
and you can see over here the 120 volt lines and these are pretty straightforward
because they only have one place. And you just plug in this hot 120 volt
out to whatever... I'd have to look at what this is... this is either lights or an outlet
and that's quite straightforward. Now, with the 240 volts, it's actually just as straightforward.
Now, with these two, and I want to clarify that this is a dead panel, so nothing, if you're
working on this, don't fry yourself, turn off all the electricity. But if you look at this you've
got your two incoming power lines and the way they come down is they separate so you have if you look
at this one versus this one this panel, or excuse me, this circuit breaker is actually attached
to this line as the hot and this circuit breaker isn't actually attached to this line as hot.
Now what happens is if you have something like this, this is our 240 volt 50 amp this is for RVs,
we have an RV plug so if somebody comes and visits us they can just back up to the shed and
plug in and be good to go. This one is actually touching both of them and so now you're getting
that out-of-phase that 90 (*actually 180) degree out of phase 240 volts because as this one peaks
high this one peaks low so even though it's up 120 that's down 120 and you get your 240 volts.
Now most of the time when you're doing wiring, if you're dealing with like 12-2, 10-2, 14-2,
all of those things like we discussed in our ampacity video, you only have your two conductors,
you have your black and your white. However this, since this is THHN, you just run an extra wire.
Now the electrician that ran this obviously just had a lot of black wire. So instead of running
a separate red wire, he took a black wire and wrapped it up with red tape. But if you have the
time, the ability, or whatever, you can get a red wire. Now, when you are dealing with AC systems,
black wire is hot, white wire is neutral, green or bare wire is ground, that's safety ground,
and then red wire is typically your other hot leg but it can also be something else. It can
be a communication line, it could be something else, it's more of an “other” category. But in
this case it gives us that second “hot” line. So, if you have a 240 volt system that you need,
you have to have a double breaker like this that can tag onto both of these lines. And then
you put black into one and red into the other and then run it to where you need to go. Now,
if you have a 240 volt outlet that doesn't need neutral, then you'll only run these two and ground
but a lot of times like on a dryer, it'll be black, red, neutral, and ground and so you'll need
to run four wires - three conductors, one ground wire to your device and that's that's really it.
You need to make sure you have the right circuit breaker. If you have one that only has one spot
like this, it's not going to work for your 240 volts. You're going to need something like this
that accesses both sides of the power coming in so that you can get it to your source.
So that's it! I mean, I'm not sure exactly how exciting that was. Hopefully that helps you
if you have any questions, you're like, “Oh my goodness, I have something that
needs 240 volts how do I even do it?” - that's really it. You can go and you can get 240 volt
circuit breakers, the two pole I think is what they call them 50 amps, 40 amps, 30 amps, 20 amps,
I don't think I've seen 15 amps but you can get them of varying sizes and frankly I'm hoping to
get a dust removal system in here and so I'll probably have to get a 20 amp 240 volt system in
this box eventually. When I get around to it. Hopefully that was helpful! Hopefully that helped
you understand exactly what's going on in these boxes and make it so you can set up a 240 volt
system in your house or your shed or whatever. If you're not sure, if you're not confident,
if you think, “Oh my gosh, I might blow something up,” please do call an electrician, don't hurt
yourself. But hopefully this will at least make it so you can talk intelligently to the electrician
and know what they are going to do. If you liked this video, give it a like, subscribe to our
channel, please join us as we - very soon - go back to our electrical engineering topics about
circuits, control systems, embedded systems, and all that very very fun stuff and we get away
from this practical yet very very useful stuff. All right! Hope you liked it. Have a great one!