What up? Everybody? Welcome to another episode and let's ask Paul the podcast
where I, Paul Abernathy, do my best to answer all of your pressing
electrical code related questions or anything related to electricity or the National Electrical Code,
or the secrets of life and all that kind of good stuff. If you
want to take part in it, all you gotta do is go to Paul
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anything, and it's a portal that was put up a couple of years ago
to allow me to be able to address questions that people have. And it's
kind of evolved because originally everybody knows my love hate relationship with social media.
And when you have that love hate relationship with social media, you start to
notice that you got to be there. You have to be there, it's
just part of business. But then you look at all the comments and you
realize that people just struggle. And the problem with social media is that everybody
seems to think it's gospel and they listen to it, and people start propagating
misinformation, falsehoods, and it's kind of like that thing you'll met, that
little exercise where you get about ten people together and you whisper something in one
of them's ear, and then they share with the next person, and the
next person and the next, and by the time it gets to the end,
the story is totally different. That reminds me of social media, okay,
And the problem with it is some people believe something so passionately that even
if they're wrong, they're going to argue it until they're blue in the face.
And that's never a good thing for education. So while I believe that
social media can be an important tool when it comes to education, it can
also be detrimental to proper education, spreading valid information, that type of thing.
So I had to take it in with the moderation and realize that it's,
you know, consider the source. You know, consider the source when
you're when you're doing this social media shopping when it comes to knowledge. Okay.
Okay, So, as you've probably guessed by the title of this episode,
on this Let's ask Paul, somebody asked me to talk about finding amp
fridge ratings and the different ways that we can find amps for something and how
we might do this. Okay, So I figured I would kind of do
that and kind of break things down the best I can to help people understand.
How would I, you know, calculate some of the things to find
ampriage ratings depending on the question or what's presented. Okay, so that's what
you're in store for today on this episode. And so I'm going to be
spitting out some formulas. Okay, that's right. We're going to be spinning
out some formulas that you can pause and jot down if you want, or
you can just listen to them and that type of thing. And so we
will be coming out with a pocket card that has all of this information on
it, and we currently have one available for voltage drop, so make sure
you go check that out over on our website fasttracksystem dot com. That's f
A S T t R A X S Y S T E M, so
exactly how it sounds fast tracks with t r X system dot com. And
if you go there, you go to our store, you'll see that we
have the voltage drop cards. They're pretty neat and even on the other side,
I show you how they actually come up with the K value that you
use in your equation, so I kind of show you how to do that,
but I also give you the formulas and things like that. So it's
a nifty little card to have in your wallet because you know, voltage drop.
Even though it's not a mandated requirement by the ANC except for sensitive electronic
equipment or fire pumps, it's talked about a lot and it can have a
negative impact on the efficiency of your circuit and the things that are plugged into
that circuit. So it is definitely something to be taken into consideration, and
most engineers do. Most people I know do, even if it's not a
mandatory requirement by the ANYCA for again, anything other than sensitive electronic equipment or
fire pumps. Okay, so other than that, it's purely optional. But
again it is something that people tend to take into consideration, and it can
affect the efficiency of whatever the load is because certain equipment like to run between
a certain voltage range, and if your voltage drops out of that, then
it's going to be any fission prematurely cause the product to possibly fail. So
things like that have to be taken into consideration. All right, let's talk
about single phase. When we're talking about finding the amperage values on a single
phase given a couple things. So if I happen to know what the watts
are, the volts are, and I happen to know what the power factor
is for a specific single phase load, and I'll give you an example.
And in an exam type of question, they're probably going to give you all
of these values, and if you don't know what the power factor is,
then you go to unity. You can do one point zero zero if you
want. But if they give you a power factor, then obviously when we're
dealing with amperags, we want to take that power factor into consideration. If
they're giving you that type of question, that has power factor in it,
right, So let's look at the first one. So if we know what
the watts are of the load, the formula is P over E times PF,
PF being power factor, E being voltage and peving the wattage power.
So if I gave you a question and it was one hundred and fifty watt
load, and I told you that there was a power factor of eighty six
percent or point eight six, if we work it into a decimal, go
from the right side of the six move two spaces to the left point eighty
six. Always try to put percentages into decimals when you're doing your math.
It's a should be common knowledge by now, but just remember to do that.
And then, of course we give you the actual voltage, which is
two thirty volts. Again, folks, just to remind you, use the
values they give you in the equation. If you're doing an exam, if
they tell you it's two thirty volts, and you're in your mind thinking,
well, wait a minute, this is a two forty volt circuit. No
use what they give you, okay, Use what they give you, okay.
So in this case, it would be one hundred fifteen hundred watts divided
by e, which is the voltage times the power factor. So the first
thing you want to do is always work the multiplication out first the lower part,
So two thirty times point eight six. So I'm going to work it
with you. So two thirty times zero point eighty six, and that gives
us one ninety seven point eight. So now it's fifteen hundred divided by one
ninety seven point eight. So fifteen hundred divided by one ninety seven point eight,
that's going to give me seven point five eight. Three. Drop the
three, so it's seven point five eight is the amps? Okay? That
is the actual amps that is the current that we have for this equation,
okay, and that took power factor into the equation. Now, interesting is
if power factor wasn't in the value, then it would be fifteen hundred divided
by two thirty and that would be six point five two. Okay, So
it's uh, you know, the power factor is making it not as efficient.
So the current went up, but if you take that out, that
can be a different that's a difference of about one amp, believe it or
not due to that power factor. Okay, So you want to make sure
you're using whatever they give you. Definitely want to use what they give you,
all right, So let's see here. So that would be an example
when we know the WHTT is the voltage and the power and a power factor
if it's available for the question. So the next thing you might get a
question it says, what if I want to know what the answer are and
I've got a load with a motor it's a horse power, but I don't
know how to figure it out. Then they give you a power factor,
they give you an efficiency and you're like, okay, well it tells me
that it's an efficiency rating of ninety two percent, and it tells me,
it's a power factor of eighty okay, and you may get this from the
name plate of a motor. It's single phase and it tells me it's one
hundred and fifty volt motor, and it's telling me that it is a half
horse power half horse power. Okay. So immediately what some people would do
is they would run to the back of the of motors and go to the
FLC. But that's not what you do here, Okay, that is not
what you do in this scenario. The equation is, now you do do
that when you're sizing for motors for short circuit ground fall protection, when you're
sizing for the conductors. All we're doing here is finding the amps based on
a question where it asks you specifically to find the amps based on working this
out. Okay. Now, interesting enough, this is probably going to be
further in lined with what's on the name plate versus what's within the FLC because
the name plates typically take things like efficiency and power factor into the equation.
So this is going to probably harmonize more with what you would see on a
name plate rather what you would see in an FLC, which is in four
thirty nine two fifty. Just remember the FLC is what you're going to use
in the code when you're sizing brand circuits, feeders from motors and motors,
short circuit ground protection, things like that. And when you're doing the overload,
you're going to use a nameplate. So all I'm showing you is if
they ask you a simple question and want to know, what is the AMP
load for a single phase half horsepower one hundred and fifteen volt motor that has
an efficiency rating of ninety two percent and a power factor of eighty, how
do you work it? Well? This formula which I encourage you to jot
this down in your codebook if you have the If you're not preparing for an
exam, you can write any damn thing you want in your book. If
you're preparing for an exam, be careful make sure that they allow you to
write in your codebook. And how do you determine that? Then you've got
to go to the test center. Maybe they have a bulletin that you can
look at, like PSI, if that's who's doing your testing. They will
have what's called a guide in a bulletin, and it'll tell you what you
can and what you can't do. That type of thing, So just be
aware of that. And in your codebook if you can write in your codebook,
like for example Texas, you can jot things in your code book if
you want. The best place to do this is up near the front where
the code panel members are because there's usually a lot of blank spaces up there
or a lot of room to write stuff, and so it makes it nice
to be able to jot your formulas, your owns low wheels, you know,
example of a parallel series circuit, all those type of things, all
the formulas. That's a great place to do it. But again, don't
say Paul told you to do it. You get in trouble. You need
to know whether or not you can mark in your codebook, and you're going
to have to check with the bulletin or your test center wherever you're at in
the country. So here's the formula. So the formula is horsepower times seven
forty six. So that is the formula. Seven forty six is the actual
wattage for one horse power. Okay, so it's horsepower times seven forty six
divided by the vaults times the efficiency times the power factor. Well, remember
what I said, you want to work the multiplications out first, So work
the top out and work the bottom out. So let's worked the top.
So we said it was a half horse power, right, so you take
the one divided into two. That gives you point five. If you look
at it and you know that half a horse power is point five, whereas
one horse power is one point zero. Okay, you should know that,
I hope, So point five is our horsepower. So we're going to do
point five times seven forty six and that gives me three seventy three. So
that's the top part of this equation. Now the bottom part was the voltage
times of power factor. And remember we want to convert everything into decimal So
we started the right side of the percentage and move two decimal spaces to the
left, so that means that ninety two percent ends up being point ninety two,
and then the eighty percent same thing. Start from the right, move
two spaces to the left. Now that is point eight zero. Now let's
do the multiplication. So one hundred and fifteen times point ninety two times point
eight zero, and that is eighty four point sixty four. So now all
you do is divide the top three seventy three into the bottom eighty four point
sixty four and I'm going to do that now eighty four point sixty four,
and that gives me four point four amps. So that is my answer when
the horse power is unknown, but we do know what the horse power is,
okay. Okay, So that was that was easy, right, So
that's when the horse power is actually known, means you know what the horse
power is. I don't know if I said you don't know it, but
you actually know what the horse power is. Okay. So the next one
is, okay, well, what happens if how do I find the amps?
If I the kilowatts are actually known, so I happen to know what
the question gives me kilowatts? Okay, same concept here there's no motor,
so we don't worry about the efficiency. So here it's saying, okay,
let's look at this question. It says I have a two hundred and thirty
volt single phase circuit which has a twelve kW power load, whatever that may
be, and it operates at eighty four percent power factor. Determine the current?
Okay. So that's kind of a question that you may get on an
exam. So how do I determine what the current is based on the fact
that I'm giving the voltage, I'm giving the kilowatts, and I've given the
power factor. Well, this formula is very similar to what we did with
the previous one when we knew what the horsepower was. This is a little
different though, since there's no horsepower involved. We don't equate the seven forty
six. That has no play here. So now it's just killowatts times a
thousand divided by volts times the power factor. Okay, so we know that
it is twelve kilowatts, so we could skip one here and just go we
know that twelve kilowatts the k is Kei low, so we know that it's
twelve thousand watts. Okay, you could skip that one, but if you
didn't, you just go twelve times one thousand, So that's twelve. And
then on the bottom part it's the voltage times of power factor. Well,
we said it was eighty four percent power factors. Start from the right of
the four, move two spaces to the left. Point eight fours now are
our multiplier, So we do two thirty. Remember, use the voltage they
give you times point eight four, and that is one hundred and ninety three
point two. Now that we have it figured out. We do the twelve
thousand divided by the one ninety three point two, So it's twelve thousand divided
by the one ninety three point two, and that's going to give me sixty
two point one one. Remember that we can drop anything that is what under
point five, So this is point one one, so we drop it.
So the amps is six sixty two amps. So that's what our amp is
for that twelve kW power load right at two thirty volts with an eighty four
percent power factor. Okay. Now, again, these are just questions you
may get on an exam and you're sitting there going, okay, I don't
know how to work the power factor. I don't know how to work the
efficiency. And that's that's why we're doing this. This that's what this episode,
this podcast is all about, because I do get a fair enough questions
that people ask about that. Okay, all right, Well, so this
next one is one that says, Okay, let's assume we give you a
question and we actually know what the kVA is or the kill of volt ampiers.
Okay, so in this question, it's one hundred and fifteen volt circuit.
It's a two kVA or y'all know k mean two thousand va. Vault
ampires single phase generator operating at full load will deliver how many amps? Okay,
how do you determine this one? Well, in this formula it is
k it's the kVA or the killer vault Dampier's times a thousand, So that
would you know, you'd be two times a thousand because it's two kVA,
or as you as we said before, if you know already that two k
va equates to two thousand va, then you can skip that little math,
and so the top part would be two thousand and again, the bottom part
is the voltage, which is one fifteen. So this is going to be
two times one thousand divided by one fifteen, or in our case, two
thousand divided by one fifteen, and that equals seventeen point four amps. So
you just take two thousand, you can divide that by one fifteen, and
you'll get seventeen point three nine one three. Obviously in this case three nine,
you can work it up to seventeen point four and you're rounding it up.
Okay, that's so that is okay, all right, So and we're
working this. When we work this to the all the way down to the
simplest form. Okay. Now, remember ampier is the rate of flow of
currents. So this is again full load. We told you that it was
a full load being delivered, and that full load on that one hundred and
fifty volt two kVA. We didn't work anything, We didn't drop. It
is full load, full being drawn. That full two kVA is being drawn.
That would be again seventeen point four amps. Okay. So now up
to this point, all of these that we've done have been pretty straightforward.
But if you remember something, every one of these is dealing with single phase.
So what do we do differently if we're dealing with three phase? Well,
the only difference, folks, is that you're going to be throwing in
the value of one point seventy three to two, which is a square root
of three, okay, when we're doing three phase, because there's three legs
square root of three. Okay. So if we know the watts the voltage
in the power factor are known, then that equation is I equals p which
is the watts divided by E times PF, which is power factor times one
point seventy three. Okay. So in this case, the only differing variable.
It's still a fifteen hundred watt load. The power factor is still eighty
six percent. Y'all know how to convert that to point eighty six. Right,
start at the right of the six two decimal spots to the left.
You get it, and it's a three phase load with two hundred and thirty
vault source. Okay. So in this one is fairly simple the same way
we did before. The p here is fifteen hundred watts, the e is
two thirty, the power factor is point eighty six. Remember eighty six percent
converted to decimal and then times one point seventy three, which is the square
root of three, because it is a three phase. So in this case,
it would be fifteen hundred divided by two thirty times point eight six times
one point seventy three two. That is three hundred and forty two. Okay,
And hold, let me go in and let me work this all the
way out. Two thirty times point eighty six times one point seven three two
is going to be three forty two point five, okay, And so we'll
just say at three foot two five. Now, one of the things we
do at that point is take the fifteen hundred and divided by three forty two
point five, and that's going to give me four point three seven, which
I can round to full point four, and that's going to give me four
point four amps. Okay, Now what if same thing? Now what if
we have the same equation and they give you the horse power and they want
to know what the AMPS is on this three phase Again, it's just like
what we did in single phase. The only difference is we're adding that one
point seventy three to two to the lower portion, or the denominator portion of
the equation. Okay, remember when I say that though, folks to people
not to get confused when I talk denominators and numerators and stuff like that,
that you know the difference that the denominator is the bottom part, the numerator
is the top part. So we're talking the denominator here is the bottom part.
Okay. So how do we do this one? So same scenario.
We have to know what the horsepower is. So let's read the question.
Determine the AMP load of this three phase half horse power two thirty volt motor.
The motor has an efficiency rating of ninety two percent, and this is
very much going to be in line with the nameplate, by the way,
and the power factor of eighty percent. Okay, Well, the first thing
I like to do is convert all of these percentages into decimals, so that
ninety two percent becomes a point nine to two, that eighty percent a point
eight zero, right. And so now since we have the same half horse
power, I'm gonna vide the one into the two. That's how I get
the point five. Although you probably know a half of one horse power is
point five, I'm just kind of talking through it for you. So I'm
gonna haveo point five times seven forty six, and so the top part is
gonna be three seventy three. Okay, that's the numerator portion, and then
the bottom part I've got to do the math. So two thirty times point
ninety two times point eight zero times one point seventy three two is two point
two nine three point one. So I can just take the two nine three
and drop the other. So now I just take the three seventy three,
divide that into the two ninety three, and that gives me one point two
seven ampires. Okay, so that motor and that's probably gonna be more in
line with a name plate Okay, not the same as the FLC, which
we're going to use for sizing circuits and a short circuit ground for protection,
because the code tells us too. Right. This is kind of if you
happen to get a question that's asking you to calculate this out, this is
how you would do it. Okay, makes sense. Okay, let's keep
going and kind of finish these out. So what if I have a three
phase and I actually know what the kilowats are? So the only thing that
you're changing with versus what you did with the single phase is that one point
seventy three to two. So if I know what the kilowats are, what's
the question? Okay, it's two hundred and thirty VOO three phase circuit now
with a twelve kW power load that operates at eighty four percent power factor,
determine the current Okay, simple question. I'm going to say, Okay,
well, I can skip one step of doing the kW times one thousand,
because I think we all know that twelve kW is twelve thousand watts, so
I can skip that math. So that's going to be the numerator. That's
the top part. The bottom part is the E time PF times one point
seven three two, So we know that it is two thirty and I'm gonna
work the math two thirty times, and we turned our eighty four percent into
a decimal point eight four, so times point eight four times. And then
of course the one seven three, which is a square root of three times
one point seven four. Excuse me, one point seven three, So I
don't know where I was getting that from. All right, times point eight
four times one point seven three, which equals three hundred and thirty four point
two three. Okay, So it's two three six, So we're gonna round
this to three thirty four point two four, all right. So then you
just take the twelve thousand, which is in the numerator's position, divided by
three thirty four point two four, and that gives me a total of thirty
five point nine zero. So we're gonna round this to thirty six ampiers.
Okay, So the answer here is thirty six amps. Okay, so that's
what the ampload is, uh for the cur draw is for this motor at
this power factor. And then lastly, well, well we'll end this out
on this episode with if you know the kill of old amp here, and
you guessed it. It's essentially the same as we did before, except for
the top part is the kill of volt ampier times a thousand. Well,
I think we all know that if it's like a four kVA, then that's
four thousand, so you can save a little step there. But if you
didn't know, then you take the kill of old ampire, which if it
was four kill of old ampiers, you do four times one thousand, four
thousand. So what's the question? A two hundred and thirty volt four kVA
three phase generator operating at full load would deliver blank amps. Okay, how
do we prove it? Okay, Well, the equation is kill of old
ampires times a thousand divided by e times one point seventy three to two.
Well, we know the kkva was four, so four times a thousand,
so the top numerator is four thousand, and then the bottom is going to
be two thirty times one point seven three, and that is gonna give us
three nine seven. Now, by the way, if you wanted to go
all the way out at one point seven three two, you could, okay,
but you're gonna get roughly the same values as using one point seven three.
But if you want to work it all the way out. That's fine.
If you want all of the square root of three, that's fine.
I'll show you the difference if you want to see it. For somebody out
there, I know this hollering saying, Paul, it's not one point seven
three, it's one point seven three to two, okay, whatever, I'll
do both for you. So in this case would be two thirty. We're
doing the denominator portion two thirty times one point seven three, and that is
three three ninety seven point nine. So I'm gonna take the four thousand.
I'm going to divide that into three ninety seven point nine, and that gives
me ten point zero five ams, so it's ten ams. But okay,
Paul, Paul, you need to use the one point seven three two,
okay, okay. So I'm gonna go two thirty times one point seven three
two, and that gives me three ninety eight point three six. Okay,
So three ninety eight point three six is my value. I would just use
three ninety eight. Drop the point three six, so I would go four
thousand divided by three ninety eight, and that gives me ten point zero five.
Still drop the point zero five, so it's still ten amps, folks,
it's not gonna make a difference. But if you want to use one
point seventy three to two all the way out, go for it. Now.
You can do that if you like. Don't make us complicated, please,
it's not it's not worth making it complicated, all right. So that's
how you find the amps, whether it's single phase, whether it's three phase,
and you ask these kind of questions where they give you the kilowatts,
or they give you the killer vault damp years, or they give you the
watts the vaults and the power factor, or maybe when the horse power is
known, they give you all these other variables. These are ways that you
can answer these questions to find the ampage. Okay. So that's the whole
purpose of this episode was called finding the amps based on the questions. And
obviously normal OHMS law is pretty simple, right you have the E R Okay,
so E the voltage divided by are the resistance will give you the current
right, which is I. But here is just a little more complex when
we're trying to find the amperage values based on whether it's watt's volts and kind
of throw in the power factor scenario in or things like that because people ask
about that. And also it was important to talk earlier about the horsepower for
single phase versus three phase, just so you have kind of an understanding on
how this all works. Okay, all right, folks, hopefully you got
something out of this episode. Again, we're just talking amps, and that
was it, And maybe we'll have another episode and I'll talk about maybe how
to find horsepower, how to find wattage or whatever. If that's what you
want, we more certainly can do that until next time, folks, Stay
safe, God bless and we'll catch you on another episode