This video has had something like seventeen
false starts.
I’ve gone down a number of rabbit holes trying to understand a bunch of things,
and I had at one point committed to making an entirely different video because of that!
But then I ran into a number of conceptual hurdles
that I don’t have the energy to
address right now
so we’re back to the simple scope of that first one.
Now, I’m gonna be honest here, my main point
with this video is to address a grievance
I have with how the rest of the world seems
to understand the United States
(and more broadly North American)
electrical system.
While it’s true that we have terrible, barely adequate receptacle designs
and our kettles are slower
than yours,
here’s a fact about us that I think will blow a few fuses out there;
The US is a 240 volt country.
I can hear a lot of you going
whaaaa????
[with obnoxious buzzing and other sound effects added]
But it’s true!
We have 240V in our electrical panels and at our disposal.
You’ve heard about our obsession with air conditioning, right?
Did you really think we’re cooling
our gaudy McMansions with a machine we just
plug into a regular outlet?
No.
And some of us have electric stoves,
electric water heaters,
clothes dryers,
and even electric vehicle
charging now!
We’re not doing all of those things with a measly 15 amps at 120 volts (Or 1800 watts).
How are we doing it, then?
Let’s take a trip to the other room where I have
a standard US service panel we can look at.
[electrical humming]
Here’s a standard US service panel we can look at!
It might be a little hard to hear --
[humming abruptly stops]
I'm just kidding.
I added that 60 Hz hum in post.
Did you seriously think our service panels are some sort of disastrously loud thing?
I bet some of you did.
Anyway, this building is a single family home.
That’s important because of a little
thing I’ll be bringing up later.
Now, this little wart thing on the side is a doorbell
transformer - pay no attention to that
and, uh, also, um any of the wires that might
seem a little less, uh, tidy than others
are the work of yours truly but, again - not important!
Now inside we’ll find a main breaker at
the top and a bunch of, in fact to many people
an absurd number of circuit breakers feeding
individual circuits.
But there’s still room for two more!
The main breaker is a 200 amp breaker.
This home, like many and pretty much all homes built within the last few decades, has 200A service.
Now, you might be thinking that’s 200A at 120V so we have 24 kilowatts at our disposal here.
But no, that’s 200 amps at 240 volts, so in fact
many homes have 48 kW to go around.
100A service is still fairly common but that’s still 24 kW.
Plenty for smaller homes, especially
since natural gas or other types of fuel combustion
for space heating is still quite common ‘round these
parts.
Now, take a look at these breakers and you’ll find that they have their capacity printed on their toggles
and you’ll also see that
a few of them are… weird.
They take up two spaces for some reason.
Huh.
Well, those are 240V circuits.
This one’s going to a clothes dryer, this one to an air conditioner, etc.
But… why two spaces?
That seems a little weird, doesn’t it?
Well, the reason it takes up two spaces has to do with the weird way we get 240V.
You see our power transformers that
feed our homes do produce 120V.
But twice!
Yeah! It’s weird! But first, a quick reminder
of what transformers do;
They’re more than meets the eye.
Pretty much THE reason we use
AC power all over the place is that we can
use transformers to step the voltage up and
down all will nilly.
All you gotta do is wrap a bunch of wires around an iron core, and they’ll induce an electromagnetic field
which propogates through it! Then, wrap some
more wires around the core on the other side
and that field will induce a current in those
wires! Simply vary the number of turns of
wire around the core on each side and you
can change the voltage according to that ratio!
It’s pretty neat!
It allows us to transmit power through overhead or buried electrical lines running at thousands of volts.
That lets those wires carry a ton of power for their size,
because while the cross-sectional
area of any given conductor affects how much
current it can safely carry, when you bump
the voltage way up you can carry more power
(that’s watts) with the same amount of current
and thus a relatively small cable.
This allows us to transmit power over long distances economically in the near megavolt range.
Substations will step that down to a more reasonable 11 or maybe 32 *thousand* volts
for neighborhood distribution,
and right before it enters your home it is
stepped down by a final transformer which
delivers the final, relatively low voltage
to your home.
Now, normally, you just hook a couple of wires
up to the ends of the secondary winding of
the transformer and call it a day.
That’s what you’ll find in most countries around the world
when dealing with standard single-phase
electric service.
[whispers]
We’re just gonna ignore three-phase for 
right now.
The secondary
winding produces a 240V potential and thus
you get 240V out of that transformer.
And believe it or not, that’s exactly what our transformers do!
They produce 240V on the
secondary winding, just like yours.
But the weird bit is that
This is America.
We’re not gonna settle for hooking up a measly two wires to our transformers.
That is simply unamerican.
No, we must have three.
That’s one more and thus better.
Obviously.
This is where the weirdness happens!
Our transformers don’t just have taps on the ends of the secondary winding.
We put a third, central
tap right smack dab in the middle,
or center, of that winding in its middle.
And that center tap becomes referenced to Earth,
and that is what defines our neutral.
Doing this creates
what is called split-phase power.
We end up with what behaves as though there are two 120V potentials
180 degrees out of phase from one another.
Across either of those and neutral
you get 120V,
but when you go across the two phases you end up with the full 240V the transformer is producing.
So now let’s go back to the electrical panel.
I’m going to take the cover off of it so you can see what’s going on inside.
This is the part where I say
Don't Try This At Home!
There are many things inside this
box that can kill you if you touch them.
I have a fairly good understanding of what those
dangers are in here;
good enough to run a few new circuits without injuring myself or burning the house down
with, so far, a 100% success rate.
But this is not something to
play around with.
I’m showing you mine so you don’t need to see yours.
Kay?
Alright. Here’s where the magic happens.
I know, to those of you in Europe this looks horribly gross and terribly unsafe but
that’s OK. We're coping.
Up at the top there are three beefy cables coming in.
Those come from the meter box outside but
ultimately from the transformer.
The two outer cables are both live at 120V potential to
ground.
The middle cable is, conveniently,
ground. And also neutral!
Yes. That middle
cable is connected to a ground rod outside
by the meter box, in addition to being connected
to the center tap of the transformer.
For those that didn’t know this already, the
ground plug and the neutral plug
of your electrical outlets usually end up in the same exact place eventually.
Right here!
(and on the other side)
It’s weird and I don’t wanna get into it right now because it hurts my brain
and there are particular exceptions
so we’re just avoiding that whole can of
worms.
If I take a voltage measurement between this cable and the neutral,
you’ll see that it’s 120 volts (or thereabouts).
If I measure from the other cable to neutral it is also 120 something volts.
Remember those two pairs
of cables are across only half of the transformer.
Conveniently they end up in the panel in that
same orientation.
This is the left side of the secondary winding.
The right side of the secondary.
And the center tap of the secondary.
You will only get half the voltage of the
secondary if you’re across only half of its length.
But across those two outer cables you do in
fact get 240V. Or close, anyway.
Those two cables are at the ends of the transformer’s
secondary so the entire potential is there.
But you have to be across those two cables,
not just across one of them and neutral,
to get the full potential.
And that’s why our 240V circuits are on these weird double breakers.
The lugs up here feed a pair of bus bars going all the way down through the center of the panel.
A circuit breaker makes contact with that
bus bar and provides an internal link to an
output on a screw terminal.
The breaker can interrupt the current path from the bus bar
to the terminal either manually with the toggle
[two clicks as it is actuated)
or automatically in the case of an overcurrent event.
This here is all a typical US circuit breaker is.
[click]
[clack]
It’s attached only to the live or hot side of the circuit.
The neutral side of any circuit
goes directly back to the panel.
If you look in the two spaces where there aren’t a breaker installed you can see the contacts from the
bus bars that the breaker will attach to.
On the bottom of the breaker, this contact
will clamp onto the bus bar, which through
the switch contacts inside the breaker eventually
make it to the output terminal here.
The other
bit is just to physically attach the breaker
to the panel more sturdily via this plastic
peg thing.
The bus bars, though, aren’t just going
straight down the panel.
They’re a sort of interlocking comb shape.
What this does is make it so that every alternate position
down the panel is being fed by the opposite
lug up there.
In fact, you can see that one of the spots on the bus bar is connected to the right,
and the other is connected to the left.
Now, if you take a look at these
two circuit breakers, they’re both feeding
their own 120V circuits.
But they aren’t
themselves fed by the same cable up top.
Take a look - across these two breakers there’s
actually 240V.
That’s because one breaker is attached to this cable through the bus bar.
(I'm pointing to the left one)
And the other one is attached to the other.
(that's the right one)
Again, each one of these breakers is feeding
a different circuit.
If you follow the wire coming out from the breaker,
you’ll see that it joins up with a white neutral and a ground wire in one of these various cables.
Those cables; they go to the various circuits in the building
(or rather they are the various circuits of the building)
and in the 120V circuits across the black hot wire
and the white neutral wire you have 120V.
The circuit breaker
is there mostly to protect the circuit from
being overloaded and damaging the conductors,
or worse, starting a fire. But in conjunction
with a grounded appliance it will also remove
voltage should the 120V potential come in
contact with the grounded casing because that
effectively becomes a dead short which will
trip the breaker more or less instantly.
But that’s not important right now.
But remember, the measurement we took across
these two breakers;
these two right next to each other was 240V.
If you want to get a 240V circuit out of this panel all you
need to do is create a circuit across both bus bars.
And that’s what these weird double
breakers do.
These are called double-pole breakers.
When you install one
of these in the panel, it takes up two spots
so that it can access both phases.
These are actually
just two circuit breakers internally bonded together
so that if one half of it trips, both do.
In fact, in some cases you can make a 240V circuit with two single-pole breakers
so long as you bond their trip levers together (and they're the same size).
To be clear, not all brands or styles of breaker
allow you to do that
and it may or may not be up to code anymore but it is an interesting possible fact!
And this leads us to another interesting fact;
Many of our 240V devices over here are powered
by two hot wires and no neutral at all.
You see, the device would only need access to the neutral if it also needs access to 120V.
Some devices do, but many don’t.
Now, you might be wondering, how do we actually connect our 240V devices to power?
Do we have special plugs for that?
Yes!
But also, sometimes no!
Many devices like water heaters or air conditioners are simply directly wired into a circuit.
Sometimes they’ll go through a service disconnect (which may also have fuses in it)
depending on the code and the device.
Some other devices, though, do have plugs.
We have weird plugs
galore over here!
See this clothes dryer? It’s plugged into this bad boy!
This 7.2 kW electric vehicle
supply equipment?
It’s got one of these on there!
Did you catch that the dryer’s plug had
four terminals
but the charging station only had three?
That’s right, the charging station
just has two hots and a ground.
No neutral connection whatsoever.
But the dryer has a neutral, too.
Likely the only thing that actually needs that is the little light bulb inside.
Or maybe the motor is a 120V motor, the same for a gas-powered dryer
[hard cut to lo-fi jazz]
And yes there is a typo on here, of course there is.
If Premiere could add a basic spell-check to the titling tool that would be fan-friggin-tastic.
I'll stop with this so you can read that up there ^^
but the heating elements obviously need 240.
But the charging station doesn’t need 120 at all so it just has the two hots.
Now I’m sure many of you are asking,
but why do you even do this?
What’s the point?
Who is Max Mouse?
Well, here’s the neat
thing about split-phase power.
Even though we have access to 240V circuits, nowhere in this building (or indeed in this panel)
will you find a wire with 240V potential on it.
Except in really bizarre or intentional scenarios, you cannot get an electric shock at 240V potential.
You have to be touching both hot wires.
Even in a 240V circuit, the individual wires are only at 120V potential to ground.
And that makes our electrical
system at least somewhat safer.
I can hear all of you screaming
“It’s not the voltage that kills you it’s the current flow!
It’s the volts that jolts but the
mils that kills.”
You’re right.
But have you considered this;
with any body of given resistance, the current flowing through it is proportional to the voltage.
I don’t know if you’ve heard of this little equation, 
V=I•R
That’s voltage is equal
to current times resistance.
When you increase voltage, that makes current go up, too!
And it’s not like American bodies are a lower resistance than yours
Is 120V “safe?”
No. Of course not.
You do not want to come in contact with it and it can still very much kill you.
But, in any given scenario, if someone is receiving an electric shock
the voltage matters!
You will always lower the likelihood of significant injury or death if the voltage is lower.
There isn’t some magical point at which voltage suddenly becomes dangerous.
And without enough voltage, your body won’t pass any current at all.
I mean, take a 12V car battery as an example.
It can produce literally hundreds of amps; many more amps than my circuit breaker panel can supply.
But 12V is not enough pressure to
send any of that current into your body
except in really weird circumstances like electrodes
piercing your skin.
People get really hung up whenever I’ve
mentioned that 120V is safer because I guess
they think I’m saying it’s safe?
I dunno.
I’ll be clear, it’s not safe!
And in fairness,
any safety benefit we might get from it is obviously negated by the fact that our plugs are so terrible.
I mean, the entire pin’s length
is conductive.
You’re just asking for a shock when you plug anything in.
It literally just takes holding it wrong.
And these big plugs are even worse!
Plus, we have dumb-as-rocks
circuit breakers in most homes and only put
leakage current detection devices in bathrooms
and kitchens, so yeah.
We have way more opportunities to be shocked, and that is itself a huge problem.
But, it doesn’t negate the fact that, all else being equal -
and please understand what I mean by that;
in any given scenario where one is receiving an electric shock
- a 240V shock is unquestionably worse than a 120V one.
Yes, 120V is still very dangerous! It can still kill
you! You still want to not be shocked!
That is priority one.
But it is at least marginally
safer all else being equal.
Now to be clear, it’s not just for safety
that we’ve done this.
In fact, likely that’s just a happy accident of our history
going back to the AC/DC wars.
[metal music plays under AC/DC]
And for what it’s worth we never had quite the hardship
finding raw materials for building wiring
so the thicker cabling required for 120V circuitry generally wasn’t a huge consideration.
Meanwhile in much of Europe the savings allowed by using 240V were substantial
especially in the wake of World War II.
And then there are the ring mains
of the UK.
Look those up if you've never heard of them.
They’re weird.
And, fun fact, in the UK they actually use split-phase
power on construction sites!
In that case, the potential across the two wires is 110V funnily enough,
with each wire only at 55V potential to ground.
This is done for the express purpose
of increasing safety!
55V is even more safe than 120.
55V is barely above what power
other Ethernet is.
Anyway, since the stuff used on the construction sites is wired across the phases, it all runs at 110V.
So I guess a fair number of UK power tools can be used
over here.
Whaddya know.
Yeah - quick note, for some reason lots of
people will refer to our voltage as 110V
(and thus 110/220)
or maybe 117 or 115 or even
125.
OK, to those of you who do that, just…
it’s 120.
But there is no concrete exact
voltage to any electric grid.
It varies depending on conditions so everything operates within a range of acceptable voltages.
Usually here I get something like 123V but in other
places you might only have 115V.
Or maybe even 110. It’s fine, stop being pedantic
about it.
Anyway, that’s all I really wanted to share
with this video. A basic overview of the US
electrical system so everyone is clear on
the fact we have 240V power.
It’s a little weird, but it’s there and we do use it.
It’s not like we’re in the dark ages.
Oh right, and wait, that thing about the fact
that this is a single family home being important!
Ah!
Recently I made a video about fans and motors
and how single phase power makes motors hard.
Well, in that video I talked about how in
an apartment building you might have 208V power
rather than "the standard 240."
That seemed to confuse a lot of people,
especially those of you who until right now didn’t know that we have standard 240!
Apartments often have 208v in their service panels
because many larger buildings are hooked up to a three-phase power supply.
When done in the most common Wye (Y) configuration,
each phase is 120V respective to neutral, but across any two phases you have 208 volts.
In those buildings, your electrical panel
will be extremely similar to that of a single-family home.
There will be two hot phases as well
as a neutral.
But, those two hot phases are not from a split-phase transformer,
but are in fact two of three available phases from a three phase transformer.
And it’s the difference in phase angle, 120 degrees versus 180, that makes the potential across the phases
208V and not 240V.
It’s actually geometry! In a way.
Or is it trigonometry? Whatever.
Most of our devices which are designed to
operate on 240V will happily operate on 208V as well.
In fact, they’ll often specifically
have labels on them that say 240V / 208V.
The only real downside of 208 is that devices
which produce heat will only produce 86.7%
of what they would on a 240V circuit.
So, if you live in an apartment building, your stove will be just slightly less hot than it might otherwise be.
Or, if you have an electric vehicle charging station installed on 208,
it will charge slightly slower than it would on 240.
But, not a big deal.
Thanks for watching! I hope you enjoyed this and, if you didn’t know this about the US, have been enlightened.
And will stop badgering me about only having 120V.
Just about the only
way we’re held back by our weedy little outlets
is portable things that make heat.
Yes, our kettles and pretty much everything are capped
at 1.5 kilowatts for an 80% safety margin
on a 15A circuit, but really…
aside from space heaters and tea kettles nothing is worse for being capped at 1500 watts.
And when we need more than that we have options.
We always had.
Yes, our electrical system is very very flawed
and our receptacles do just suck.
Really they’re awful. They’re just terribly unsafe.
But; specifically to Brits and Australians -
your obsession with switches on receptacles makes
no sense to me.
I’ve received many befuddled comments wondering how we’re supposed to turn things off without unplugging them.
Well, first, all of our stuff from vacuum cleaners
to toaster ovens has its own power switch.
Like - do you just not have that?
Do companies design stuff for you assuming you’ve got that little switch?
Because that’s not my problem.
That’s your problem.
Yes we leave stuff plugged in all the time but other than
electronics stuff it’s not consuming any power at all!
I remember one comment I read saying
that the fact our outlets don’t have switches on them
must be "yet another sign of us being wasteful
Americans."
[inhales exasperatedly]
No. There are many many signs of that but this isn’t one of them.
You will never
convince me that your switches on sockets
are anything other than a mild convenience.
And for what it’s worth, we put switches on our power strips
so we have that option for addressing electronics with standby lights and vampire drains.
Oh but what about safety?
My rebuttal?
Just unplug the thing!
You had to reach for the socket anyway to flip that
switch.
It’s not my problem your plugs are so awkward.
And no, sparking is not dangerous.
A spark from inrush current won’t hurt anything.
Really, some of you seem so scared of various
electricity things.
I don’t get it.
I mean, shaver sockets?
Really?
Just put an RCD in the bathroom.
And for being so afraid of that your electric showers are baffling.
Really, I know our electrical system has its flaws
but your perception of how dangerous electricity
is seems really out of whack.
And ring mains?
Really? What year is it?
Now, to be fair your fuses
in the plug; that's pretty cool.
I’ll give you that.
Though they do seem like quite a foot
hazard.
I guess, which is worse?
Shock hazard from 120V or foot hazard from UK plugs? 
[music fades in]
Someone should do a study...
Anyway, I really think that you guys just need to chill out over there, electricity’s not gonna kill you
it’ll be fine…
♫ electrifyingly smooth jazz ♫
That’s what you'll find in most countries
around the world when deal…. Ooh.
[exhales exasperatedly]
To get that full potenti… oh shoot, that’s
not the end of the sentence.
But you have to be across those two cables,
not just across one of them and neutral [stops]
To get… mahhhh 
[as he realized he stopped mid-sentence]
And it can still very much kill you, but….
Oh... Yeah, that’s not how the line’s written.
...terminal… this other bit is just to….
[stares befuddledly at the circuit breaker]
Yeah I got that backwards!
I lost…
I lost, I already lost track of which side is which.
Which one is which? Ii is….
This side.
Yes. Our kettles and space heaters…
Oh...
I don't want to see another *laughs in 240V* comment on the internet, OK?
All y'all better have learned now.
And, by the way, I timed my 120V tea kettle.
2:30 to boil 750 mL of water.
If that ain't fast enough y'all are wicked impatient.
