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What up? Everybody? Welcome to
another episode of Let's Ask Paul, the

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podcast where you get to ask me
any question you want on the National Electrical

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Code, whether it's a calculation,
whether it's just an opinion of the NEC.

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Whatever you have do me a favor. All you've got to do is

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go over to our portal at Paul
Abernathy dot com. It's free, doesn't

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cost you anything. You can ask
any question you want. Many cases,

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I'll respond back in an email.
If you're selected, you will be used

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on an upcoming podcast where everybody gets
to learn from your question. And don't

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worry, I do not share names
unless you specifically say, hey, you

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can share my name. Other than
that, I do not share names when

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I do the Let's Ask Paul series. Let me give you a couple updates

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really quickly before we get into today's
episode, which spoiler alert, today's episode

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is a calculation. So I know
everybody loves calculations, but today is a

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calculation question that somebody's sent in to
me, and so we'll be going over

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that, but I want to give
you some updates. Okay. First,

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as you all know, the Just
Calculations video series is starting next month and

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so we're working on videos for that
right now. The thought is it's going

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to be a video each week,
a weekly a video, so it gives

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you something to subscribe to be anxious
each week for a new calculation and if

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you want to get into that right
now before the price goes up. It's

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ninety nine dollars annually, but it's
going to go up to one twenty five

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when June rolls around, so you
can get in now. You're locked in

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that type of thing. So all
you got to do is go to fasttrackstv

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dot com or fasttrackstube dot com and
go on and subscribe. Now you take

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advantage of it while it's ninety nine
bucks before it goes up when that exclusive

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series comes out, and you'll see
a lot of changes coming in June to

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fast Tracks Tube. It's a premiere
platform and we've spent quite a bit involved

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in development of the platform and how
it works whether it's on the mobile or

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on a desktop. So we're really
excited about that platform. So that's going

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to be our exclusive video platform,
so that's exciting to get ready for that.

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Also, we do have a bunch
of new mert that's available over on

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our website fasttracks system dot com that's
fas T t R A x S Y

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S t e M dot com.
So please do me a favorite check that

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out. And of course we still
have Electrician Pride Electricianpride dot com that has

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a bunch of swag as well,
if you're interested. Okay, so let's

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get into the day's episode. So
on the day's episode, somebody sent in

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a question that says, Paul,
can you explain the optional calculation for schools?

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And so I figured I'd take a
good opportunity to do that here in

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a podcast. Now, granted,
a lot of people are visual earners,

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and most of the time calculations,
it really takes a visual to kind of

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get it. However, when it
came to schools, the more I looked

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at it, it lended itself to
be okay for a podcast because it's basically

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some concepts that you can valid by
looking at the table, and all I'm

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really doing is explaining it to you. So if you're driving in the car,

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you're listening whatever, you don't need
to watch the car in front of

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you, don't need to worry.
You can go back and look at the

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tables that I'm going to be talking
about in your codebook you when you're done,

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I am out working out of the
twenty twenty three edition of the NEC

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So I need to make that clear
first. It's the twenty twenty three edition,

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and we're gonna be looking at twenty
eighty six for schools, and we're

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gonna be looking at the table to
twenty dot eighty six the optional method,

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Right, that's what we're going to
be looking at, all right, And

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the example that we're going to be
using today as well comes out of Link

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because I wanted to be able to
since it's a video, I mean,

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excuse me, since it's a podcast, I want and I wanted to give

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you a direct reference. So the
beautiful thing is that in Link, which

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is a product that comes from NFPA, it's a codebook in your pocket.

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Basically, the example that they give
in the enhanced content is the one we'll

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talk about, because again it just
emphasizes how simple this is. But again

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people get confused at the process.
Okay, so we'll break it down for

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you, all right, So let's
go on and look at the code.

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I'll read it to you since I
know it's a podcast, and I will

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break down the sentences and give you
extra in depth explanation where necessary on this

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one. But this is the optional
calculation for schools. Now, remember this

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is optional. You can always use
Part three, which we refer to as

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this standard method, but is the
general method other than the optional method.

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So you're given permission and you'll see
where it gives you permission here to do

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this, to use the optional but
you know you need to know how to

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calculate the standard method. So basically
it's adding up. The thing is,

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it's still a non dwelling application,
right, You're still adding up if there's

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any multi outlet assemblies, You're still
adding up the cooking appliances, commercial cooking

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appliances. You're still adding up all
these loads as you normally would, and

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you would apply the general lighting demands
as you normally would. All that stuff

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still applies if you're doing the standard
method, and you need to understand how

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to do the standard method, because
you're going to need to size the neutral

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using the standard method. Why because
two twenty sixty one, which is for

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neutral sizing and loading, is under
Part three. It's not under Part four

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where this optional method is. Now, I think what most people do,

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like you know the designers if they're
going to use this optional method that we're

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going to talk about today, I
think what they probably do is just size

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the neutral full size and don't worry
about the calc you get me. They

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just go mascrew it. It's more
trouble than it's worth, and the bigger

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the better. Size it for that
and be done with it. That's probably

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what I see the most. But
you do need to know that if you

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are sizing and neutral that you need
do need to know how to do the

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standard method, okay, or we
should say the general method under part three.

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Okay. I don't want you to
lose sight as I explain how to

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do the optional that it is so
important to understand how to do the regular

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calculation, and I think people get
overwhelmed by that. But it's just a

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piecemeal process. Apply your demands for
your outlets, uh you know the apply

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you know receptor outlets, toply your
apply your demands for your general lighting.

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You're cooking all those type of things. It's just like you normally would do.

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But I think people get overwhelmed by
it. The optional method obviously is

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so much easier, and it's really
based on you taking all of the loads

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and just adding them all up.
Okay, just taking all of the connected

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loads and just adding everything up and
then applying the demands that you have here,

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so it makes it easier. So
I think that's what most of the

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engineers who design it do. They
just take all of the loads for the

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various equipment, just add everything up
and then apply this one big, allowable

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optional method to that, and that's
how they size the service for the school.

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Okay, all right, so let's
go one and read this out and

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I'll break it down any piece that
we need to break down. Okay to

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twenty dot eighty six, and again, I'm in the twenty twenty three edition

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of the NEC In case anybody's asking, or as I always get in comments,

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people go, I'm in the twenty
twenty I get it, but I'm

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using the twenty twenty three. So
just gotta work with me here, all

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right. Two twenty dot eighty six
Schools. It says the calculation of a

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feeder or service load for schools shall
be permitted in accordance with Table two twenty

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dot eighty six in lieu of Part
three of this article. We're equipped with

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electric space heating, air conditioning,
or both. Okay. So that's the

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first part. So in order to
be able to use this optional method,

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you have to make sure that there
is either electric space, heating of some

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sort, air conditioning of some sort, or both. Okay, So you

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can use the optional method. If
they've got heating, you can use the

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option method. They've got air conditioning, you can use the optional method if

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they got both. Okay. And
when you see it, say in lieu

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of part three, that's saying that
you're permitted to use the optional method.

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You're not required. If you want
to piecemeal and add everything up and apply

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the demands we're necessary using part three, go for it. And like I

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said, you would need to do
that if you're sizing the neutral anyway,

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unless you're just gonna make it full
size and rock on. You get me,

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okay, so let's move on.
It says the connected load twich the

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demand factors in Table two twenty eighty
six shall apply include all of the interior

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and xterior lighting power that would be
all your loads, receptacle loads and all

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that kind of stuff. Any specific
equipment loads or whatnot. It says water,

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heating, cooking, other loads that
aren't pretty much in these ones that

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i'm recommending. You still have loads
you got to account for. Okay,

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so maybe it's some ev charging that
gets done at specific parking areas and that

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type of thing. Right, those
are other loads, it says, and

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the larger of the air conditioning load
or space heating load within the building or

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structure. So basically, it's just
putting everything in one big pile, and

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then we're going to apply some demand
factors to that. That's what it's basically

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saying. But there's a unique approach
to how we apply the demand factors.

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So that's what we're going to talk
about as we as we do this calculation.

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But really think of it this way. It's really throwing everything into one

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big bucket. Next, it says, feeders and service conductors whose calculated load

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is determined by this optional calculation shall
be permitted to have the neutral load determined

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by two twenty dot sixty one.
Okay, So while we might be sizing

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the ungrounded hot conductors and everything based
on this optional method, you still go

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back and you're permitted. I mean, it could be full size if you

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want, but you're permitted to go
back and use the methods into twenty dot

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sixty one to do that, So
it just it's allowing you to be able

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to do that for your neutral,
which means you're going to have to do

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a load calculation based on Part three
in order to be able to size you're

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neutral because you got to handle the
calculated neutral load, So you have to

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do a calcul on that, or
you could again do what most people do,

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They shortcut and just say screw it, full size neutral and this is

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rock and roll. Okay, all
right. Next it says where the building

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or structure load is calculated by this
optional method, feed within the building or

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structure shall have ampacity as permitted in
Part three of this article. So what

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that means is you're not going to
be using the optional method for any interior

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feeders that are feeding other panels throughout
the school. You're going to use the

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standard Part three calculation for whatever loads
that are going to be on that feeder.

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Right, so if it's a home
necroom or it's some other part of

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the building, you're going to do
specific load calculation using Part three for the

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loads that are going to be seen
by those conductors on that panel. So

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it's basically saying you're not going to
use the optional for that. That's totally

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different. Now, it also goes
on to say, you know, when

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you do that, it says,
however, the apacity of an individual feeder

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shall not be required to be larger
than the apacity for the entire building.

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Now, the reason they say that
is because if you're doing the entire building,

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as you see, you're going to
have this pretty significant demand factor applied

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that. That's because the diversity the
building is seeing. Those service or feeder

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for the whole building is seeing this
diversity across the board, whereas the individual

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feeder that may be in the building
going to a remote panel sayed somewhere else

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saying now near the gym or home
ech or auditorium or whatever it may be.

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Those feeder conductors are only going to
see the loads that are on that

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So you're sizing for that load using
Part three. But in no case,

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since you don't have the same demands
that you get for the full building,

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the reduction that there could be a
rare case where that feeder ends up being

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larger. I don't see that happening. But if it's larger, all this

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is saying is, you know what, it never has to be larger than

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what that would be for the entire
building. So that's all it's saying.

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Now again, I don't see where
you would ever have the remote panel being

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larger than what it would be to
the entire building, even after demands are

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applied. But it just reminds you
that never has to be larger, okay.

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And then lastly it says this section
which is again eighty six for schools

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under to twenty shall not apply to
portable classroom buildings. Okay. So one

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of the other big reasons for that
is the air conditioning example, for these

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portable buildings, they have to meet
Article four forty, and the lighting loads

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for those would be considered continuous loads. And so the demand factors in two

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twenty to eighty six simply do not
apply to those portable classrooms, right,

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so you'd have to do a separate
calculation using these standard calculating method covered in

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Part three for those portable classrooms.
That's not going to be what we use

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to do the overall school itself.
You with me, So you leave those

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portable things out. Now, they
may get their own service, they may

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get a feeder, and if they
get a feeder things like that, then

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you know, then you're going to
size it what totally separately? Do it

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total separate as far as the load
is concerned when it comes to those but

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you just all we're saying is you
do not apply the the portable classroom buildings

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are not added into this optional method. They don't get the demands applied to

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them. Then they may get the
value added to it using the part three

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to the overall value, they just
don't get to get lumped into this optional

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calc You with me, Okay.
In many cases, these portable classrooms may

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have their own service to them,
things like that, or they again maybe

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a feeder. And if that's the
case, then you calculate those at their

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full value, and you're going to
add that in addition to whatever your calculation

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is for the school. That's just
going to be in addition. Okay,

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Okay, So let's go on and
look in an example. So let's say

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we're given an example of a hundred
thousand square foot school and we're given and

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00:16:07,759 --> 00:16:12,000
we have to determine what is the
VA per square foot, and they also

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give us the connected load and they
say that they've added everything up and it

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ends up being two point five MVA
and mving millions. So it's two million,

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five hundred voltampires VA. Okay,
So that's our VA, and we're

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trying to find out that's our total
that's our total VA that's been given to

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us, and it's one hundred thousand
square foot buildings. So we need to

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break it down and find out what
the demand factor is going to allow us

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to reduce that VA per square foot
down. So, but we have to

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start out by finding what is the
VA per square foot. So you take

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that two point five million or two
million, five hundred VA, two million,

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five hundred thousand VA, and you
divide that by one hundred thousand because

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it's one hundred thousand square foot building, and that gives you twenty five VA

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per square foot. Now, once
you have that VA per square foot,

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Now if you look at this table, this is what we're doing. We're

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we're going to be reducing the VA
per square foot. Okay, So we

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want to get it from twenty five. We're gonna be able to apply some

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of these demand factors to this connected
load, and we're going to be dropping

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down the VA to come up with
an ultimate calculated load in VA. Okay,

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you with me, all right?
So if you look at the table.

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It says zero to three VA one
hundred percent of the VA and three

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to twenty, which is the next
seventeen over three at seventy five, and

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then everything over twenty VA per square
foot at twenty five percent. So remember

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we had to come up with what
the VA was per square foot and it's

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twenty five. How do we get
that? How do we get it?

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Again? You take the two hundred
and fifty thousand of actual connected VA that

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they gave you, divide that by
the square footage of the building, which

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is one hundred thousand square feet,
and that gave us twenty five VA per

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square foot. Now we take that
twenty five and now we can go work

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in this table and at the end
we'll convert it back to VA voltampires total

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voltampiers. But what right now,
we're trying to work an equation. Okay,

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so what does it say zero to
three at one hundred percent? So

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we've got over three, so we
know the first three at one hundred percent,

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So we just take three VA and
put it aside. Just stick it

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to the side. So as it
says over three to twenty, which equals

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seventeen, right, twenty minus three
is seventeen. So the next the seventeen,

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we do at seventy five percent.
So we take seventeen, we multiply

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that by seventy five percent, and
that gives us twelve point seventy five.

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We lay that to the side,
so we have a three VA at one

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hundred percent. We have twelve point
seventy five VA, which was seventeen at

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seventy five percent, and then the
last part that we have, which was

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over twenty was five. Remember because
the total overall VA per square foot was

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twenty five, So that last five
VA, we take it twenty five percent,

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and that is five times point twenty
five, and that is one point

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two five VA. So then all
you do, and I've got my calculator

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here, and all you do is
work it and add them all up.

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So three plus twelve point seventy five
plus one point twenty five that gives me

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a total of seventeen VA per square
foot. So do you see what the

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demand factor did here? It dropped
it from twenty five VA per square foot.

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It dropped it down to seventeen VA
per square foot. Okay, now,

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once it dropped it down to seventeen, we need to now work it

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back up using multiplication. We need
to work it back up and find out

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what is our total VA for this
building, and then of course we can

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apply the voltage and come up,
you know, with what our amps are

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for our service and whatnot. So
seventeen times one hundred thousand, So I

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do seventeen times one hundred thousand,
and that gives me one point seven MVA

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00:20:36,079 --> 00:20:41,359
or one million, seven hundred thousand
VA. Now that's quite a drop from

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00:20:41,480 --> 00:20:47,920
two million, five hundred to one
million, seven hundred. Okay, So

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that's eight hundred thousand VA. Quite
a drop because of this demand factor allowance.

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Okay. So once we have that
total VA, then we can divide

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that by whatever our voltage is for
our service, and then we can determine

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whether or not we need more than
one service to a building because of the

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allowances in two thirty dot two all
those type of goodies. But that's the

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next step you would go to with
sizing your service and whatnot. But what

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we needed to get was what is
our VA to work with, and that

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is how this table is utilized.
Now there's other people that will do this

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differently. They will apply the percentages
differently and try to come up with the

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same concept, but this is the
way it's explained in the way it's given

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in the NEC with how you do
these to the VA right, Okay,

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hopefully that makes sense to you.
If you have any questions, like always,

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you can always go to Paul Abernathy
dot com and you can submit your

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00:21:52,720 --> 00:21:55,960
follow up question. Just let me
know, be very detailed in what you're

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asking, let me know the code
cycle you're on, and there's anything you

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want me to exp plain even more, feel free to elaborate on that and

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I'll do my best to answer that
for you. All Right, hopefully I

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got something out of this episode,
folks. Until next time, stay safe,

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God bless and we'll catch you on
the next Let's Ask Paul podcast