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today's episode, what's submitted And the question is, Paul, can you
explain the application and changes that took place in the twenty twenty three n EC
for permitted reductions for neutral conductors and prohibited reductions for neutral conductors and how they
would apply to me in the field. Thanks again for all you do and
appreciate listening to your podcasts on the job site and in the car from site
to site. Well, thank you for listening. I'm glad you joined us
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or better yet, tell them about the app that they can download on
their phone. Again, won't take up any space. Okay, So let's
look at this question here. So the first thing we want to talk about
is where do we go in the code? Now I'm in the twenty twenty
three edition of the National Electrical Code, so that's what my response is going
to be based on. So if you've got a twenty twenty three edition of
the National Electrical Code, we're gonna go to to twenty dot sixty one.
Now that part of it didn't change, right, that that's not any real
change from the previous editions of the n EC, That that part didn't change.
Okay, So just want to you know, make that clear how that
worked out. Okay. Now, the only thing that really changes is in
the twenty twenty three you're you have a two twenty six two one A,
which is your basic calculation again not a change, and two twenty sixty one
B, which is permitted reduction it. The only change in this really is
giving some headings to what was B one and B two still the same,
but now they've made it clear rather than writing in the language what it was
all about, like cooking wall, amount of oven or whatever, it now
has a kind of a heading to it. So there's a B one and
a B two, same as it was before, but now it kind of
gives you a heads up. It says B one is where household electric ranges
wall amount of ovens, counter amount of cooking units and dryers, right,
very specific, and then B two is unbalanced load in excess of two hundred
amps. All right, So it's just a structural change. It's not anything
that's critically changed that's going to be too confusing. It's just kind of how
it structurally went. And then of course you have two twenty sixty one,
see which is the prohibited reductions. And again so not any really change in
that that's substant substantive. That's too much that's going to cause any confusion with
anybody. So again, now the only other thing is that I believe,
let's see here now, nothing additional that's worthy of me talking about any change
when it comes to this. So so the reason I bring all that up
because there is a wording change that has been changed in here that I'm going
to address. But I just wanted to make sure that everybody following along realizes
that whether you're following in the twenty twenty or the fact that I'm in the
twenty twenty three, it doesn't mean you can't. What I'm going to talk
about the day is not Germane to you. It doesn't matter which cycle you're
in, right, it's going to be Germane either way. Okay, all
right, so let's kind of dig into this, all right, So right
off the bat, let me tell you the change that is significant. Now,
when we did permitted reductions like this is where we took a neutral and
we could reduce the size of the neutral. It used to say that when
you permitted reduction there was an or in there when it was considering between two
twenty six two one B one and B two. So B one was the
ranges and dryers and whatnot reduction, and then the two the B two was
the portion it was over two hundred amps. Now in that it used to
be or. So it made it imply that it had you had to pick
whether or not you're going to apply the seventy percent to the cooking equipment,
for example, or the dryer. That if you did that, then if
your neutral loads were over two hundred amps overall unbalanced load that you couldn't apply
B two as well. It's kind of like an oor, you had to
pick one or the other. Well, that's changed for the twenty twenty three
because you could apply both that you could have. Obviously, a neutral reduction
can apply to your neutral calculation for ranges and dryers, for example. But
also if you're overall unbalanced neutral load based on a calculation is over two hundred,
then you ought to be able to apply B two as well for that
unbalanced load in excess of two hundred amp years. Okay, And so that's
what we're kind of going to look at look at today and how that would
apply. Now, it wouldn't be right for us to not at least explain
what a prohibited reduction is. So obviously we're going to show you how do
you apply that seventy percent and where you wouldn't where you wouldn't. But in
the prohibited reduction, which is two twenty sixty one C, we're going to
show you an example of where you're going to have to dissect out a certain
value for a let's say, a non linear load that you're not allowed to
apply the reduction too. And so people do ask, how do you dissect
this out? So that's what we're going to kind of do today in some
examples for you. Okay, we're gonna give you two examples. First example
is going to be just a normal load CALCU wherever the system may be delta.
In this case, you have all linear loads, normal loads. There's
nothing you have to worry about except we're doing your calculation and you come up
with your maximum unbalanced load based on your calculation. Okay, so let's look
at it. So when we look at the rules, we're going to focusing
today on two twenty sixty one B two. All right, and this is
for the unbalanced load in excess of two hundred am piers. Now, if
you do a load calculation and your load, whether it's a single family dwelling,
multifamily dwelling, whatever it is, if your neutral loads exceed two hundred
am piers, then you're able to do a reduction. And it's going to
tell you which ones, which systems you can do this on. Okay,
And then the course the prohibitive reduction is going to tell you what systems you
can't do this on or what condition your situation is that you can't reduce it.
Okay, So in our situation, I'm gonna give you two, all
right. So the first one just a normal, normal application and and we'll
show you an example, and then i'll explain which systems you're not allowed to
reduce the neutral load. Okay, all right, So the first example I'm
gonna give you, it's just a you did a calcu You did a calculation,
and you came up with four hundred amps of maximum unbalanced load. You
just did a standard calculation, because you remember to twenty sixty one is in
Part three, which is a standard method. Right, So even if you
do an optional method calculation under Part four when you're sizing the neutrals, you're
still going to be using Part three, right, So always good to think
that if you're in the field, you're thinking, well, I would never
calculate anything using the standard method, but you're going to unless you just make
the neutrals full size and don't want to do a calculation, then you're going
to you know, you're gonna be in Part three. So you need to
learn how to use it, okay. And anybody out there that tells you
you don't, don't trust them, and that's not an educator you want to
learn from. You need to learn part three and part four of calculations.
Right, Okay, so let's kind of look at our scenarios. So we've
got a load. We did our calc and we have four hundred amps of
unbalanced current. That's our neutral current. So in applying to twenty sixty one
B two, and here's what the code says. This say is that portion
of the unbalanced load in excess of two hundred amp piers. So that means
the first two hundred ampiers is at one hundred percent, right, Because we're
talking about the amount over two hundred amps where the feeder or service is supplied
from a three wire DC or single phase AC system, a four wire three
phase system, a three two phase system, or a five wire two phase
system. And again two phase systems in whether it's a three wire or a
five wire are rare. I'm not going to cover those, but the key
here is single phase or even a four wire three phase system, you can
reduce the size of the neutral that exceeds two hundred amps. Okay, so
the first two hundred one hundred percent. Just take the first two hundred and
that's a given. Anything over that you can reduce it seventy percent. Now,
where do we get that rule? At the very beginning of two twenty
sixty one B it says that the feeder a service and feeder supplying the following
loads shall be permitted to have an additional demand factor of seventy percent applied to
the amount in to twenty sixty one B one, And that's the value for
like ranges, wall amount, ovens, whatever. And then it says,
and a portion of the amount in two twenty dot sixty one B two,
which is the value that exceeds two hundred of unbalanced load. Right now,
that change took place in the twenty twenty three again where it says and whereas
in the twenty twenty it said or so it was almost made you feel like
you had to pick one or the other, and that wasn't the intent.
Both of them were applicable. So I can apply the seventy percent to my
range, my range for the service calc. But also at the end,
I can do an additional reduction on that neutral overall if it exceeds two hundred
amp years. Okay, Now, most one and two families are probably not
going to have two hundred amps of maximum unbalanced load, right, so that's
not going to be an issue anyway, okay, but just so you know
how it applies. So let's look at our example. We had four hundred
amps of unbalanced current. To say it's a single phase ac perfectly easiest way
to approach it, and it is two hundred amps. The first two hundred
obviously one hundred percent because we're worried about that portion that's over two hundred,
and that was another two hundred, right because we said it was four hundred
overall. You take that portion that's over two hundred within our cases, another
two hundred. You multiply that by seventy p sent and that is going to
be one hundred and forty. Am piers Well, you take that one forty
and you're going to add it back to the two hundred, which you took
it one hundred percent, and that's going to give you a total of three
hundred and forty Am Piers Well, that's going to be your maximum unbalanced load
that you have calculated and you have applied the demands, and now you're going
to size your conductors accordingly. You're you're grounded neutral conductor accordingly, okay,
straightforward, and that's the additional reduction that you can do, and remember that
is applicable in all situations, whether it's optional or standard. However, you're
gonna have to go and do the neutral calculation right now. A lot of
times people forget that you have two fifty one zero two C one, which
is titled grounded conductor. So it can't be any smaller than what's in that
table. So you need to always check the size that you calculate with the
minimum size and that table, and remember that it can't be it can't be
smaller than what's in that table. In our case, it's gonna be larger
because now we have to size the neutral for that three hundred and forty am,
so it's definitely going to be greater than whatever it would be in that
table. Okay, okay, And so at the end of the day,
we need three hundred forty AM years and we're going to size the conductors accordingly.
Now, let's look at the prohibited reductions really quickly. Okay. Now
here's the prohibited when you cannot, okay, reduce a certain portion of that
unbalanced load when it comes to the neutral, right, all right, So
let's look at that prohibited reduction. So this is two twenty sixty one C
and it says there shall be no reduction of the neutral or grounded conductor capacity
applied to the amount in two twenty sixty one C one, or portion of
the amount in C two from that determined by the basic calculation. So what
that means is, if we have a certain value that we calculated out of
unbalanced current, if there's a certain portion of that that falls under the two
items of prohibitive reduction that we're going to talk about, then that portion cannot
be reduced. Just that portion cannot be reduced, Okay, So let's look
and see overall when we can't apply a reduction, all right, So the
first one we'll look at. It says number one. So C one says
any portion, okay, any portion of a three wire circuit consisting of two
un grounded conductors and the neutral conductor of a four wire three phase y connected
systems. So if I'm having a four wire three phase y connect the system,
and I'm going to derive from it, make connections to it, and
I'm going to be deriving a three wire circuit from a four wire circuit,
and it's a three phase y system that we're starting out with and I'm connecting
onto it to create a three wire circuit that's gonna have again two hots and
a neutral, then I am not allowed to apply a reduction to the neutral.
Calculation that is going to be whatever is being supplied by that three wire
circuit that's deriving from that four wire three phase y circuit. You get me.
It's you're just not going to have to be able to do to reduce.
So whatever that might be feeding. Let's say it's feeding a panel and
it's again for lack of a better example, tapping it off or connecting or
bugging onto a four wire three phase y in order to get that three wire
two high it's in a neutral, then you're not going to be able to
reduce the neutral that's being supplied from that. Okay, So that's the first
one. No reduction allowed. So that neutral that's that's running with those three
wires, that two wires, and that neutral that's being fed from that four
wire three phase yre wherever that's going, there is going to be no reduction
on that neutral when we do that calculation for whatever that supplies panel or whatever
it may be supplying. Okay, So no reduction on that portion now when
it comes to C two, it says that portion consisting of non linear loads
supplied from a four wire why connected three phase system. Okay, okay,
So let's do an example where we have some nonlinear current. We have a
four wire why connect the three phase system, and we have a total neutral
load folks, of six hundred ninety amps on this example, six hundred ninety
amps. Okay, and that's the total that is our unbalanced current. We
did the calc. That's is what it is. But of that value,
two hundred and fifty amps of that six ninety actually is considered nonlinear current.
Okay. Well, now we have a problem. But we all we can
only not apply the reduction to that portion that has the non linear loads.
For the rest of this is obviously linear loads, okay, normal lamping,
normal lighting systems, normal motor, normal loads. They're not considered nonlinear.
Now what are non linear loads? By the way, these are things that
really are going to distort the normal sin your sort of waveform kind of causes
a disruption. You don't get neutral cancelation very easily. Things like computers,
variable frequency drives, switching devices, printers, copy machines, big office buildings
with a lot of electronic balance. All those type of things will chop the
crap out of a normal waveform, and it's hard for neutral cancelization. When
the waveform gets chopped like that, it's not a nice flow. Like you
might look into the sillioscope and it looks like a normal, nice waveform.
It chops it up and it's hard to If you think about when we talk
about neutral loads. If i have a multi wire brand circuit and I'm putting
it in a panel and I'm sharing a neutral for example, right we just
say single phase, just for simplicity sake. If I have ten amps on
leg one and ten amps on leg two, because of the cancelation effect,
the neutral will see zero. If I have ten on one and eight on
the other, the neutral will see the imbalance, which is two amps.
Okay, this is what the neutral will see. Now, what happens in
a situation we have a lot of harmonics or you have non linear loads that
is not an each a nice cancelation effect process. It doesn't take place as
nice and smooth as what we just said. So the neutral current could be
as much as or equal to any of the phase conductors, depending on the
system, so it can be problematic. And this is why you might see
four wire three phase systems with these non linear loads. You might see situations
where you see white conductors that are turning brown or whatnot, and they weren't
sized properly, right, I just say they just as an example, all
right. So what we've got is we did a calculation six hundred ninety amps
and two hundred and fifty amps of that we know is nonlinear current, all
right, So how do we apply the rules here? Probably just as straightforward
as you can imagine. The first two hundred amps, is it one hundred
percent? And then you have the non any your current, which you have
to take out because we can apply the reduction to that amount. So that's
at one hundred percent. So you have the two hundred amps that we have
to take it one hundred that we can't apply reduction two, right, And
then we have the non linear current that we can't apply the reduction too because
of to twenty dot sixty one C two. Okay, that portion that is
nonlinear, so I take that out, no reduction there, and so you
take that six ninety and you take away two hundred and take away two fifty
that leaves me two hundred and forty amps. That's the portion that we can
apply. Okay, the reduction two under to twenty sixty one B two,
So we just take that two forty, we multiply that by seventy percent.
That's one hundred and sixty eight amps. But then we apply that back to
that first two hundred that we have to take it one hundred percent. And
of course we got to apply to that non linear load, which we can't
take a reduction four. Right, we already saw that C two tells us
we can't, so we add that back. So it's two hundred plus two
fifty plus are one sixty eight that we did apply the seventy percent too.
That means the total demand that we've calculated out is six hundred and eighteen amps
of neutral load. Now six hundred and eighteen amps is a reduction from six
ninety and you know what, it could be a conductor size change. But
this is how it applies, and that's how you're going to apply to twenty
sixty one B one. Excuse me B two for the excess of two hunt
over that exceeds two hundred amps, and how you're going to apply through prohibited
reductions. Okay, and those were two examples that you know pretty much show
you how you would do that. Hopefully that that kind of makes sense right
to everybody out there, all right, So if I ask you a question
and I'll create a scenario for you that allows us to apply what we've just
learned. Okay, So the very first one, let's look at a question.
So straightforward, I'm only going to tell you the question, and you're
gonna have to assume that none of the prohibitive reductions apply because I didn't state
that they do, but I will give you an example when it does.
So this is a question, is what is the neutral demand? If the
unbalanced current of a neutral is five hundred and sixty six ams. So we'll
assume it's a single phase because nobody said said otherwise. Or we'll assume it's
maybe a three phase system four wire that wasn't that didn't have non linear loads,
right, So obviously we can apply the reduction here. So let's look
at it. So five hundred and sixty six AMS is the unbalanced load that
we're given based on our calculations, you know, standard method, we calculated
it out. So the rule here in twenty dot sixty one B two allows
me to apply the seventy percent to that portion that exceeds two hundred amps.
So that five hundred and sixty six we're gonna take two hundred away, which
is going to be a one hundred percent because we're gonna add that back at
the end, and that gives me three hundred and sixty six amps. That
is the portion that is over two hundred that's the portion that we're going to
apply the seventy percent too. So I'm going to multiply that by point seven
zero, and that is two hundred and fifty six point two amp years.
Right now, I get to drop the point two because as it says in
two twenty five, okay, that portion, we get to drop it.
If you want to keep it, it's not going to make a difference in
your equation, right But again, you can do it at the end,
or you can do it here. You can even keep it. That point
two is not going to play a role anywhere. So in our case,
we're gonna take that two hundred and fifty six point two if you would like,
and add that back to the original two hundred and that equals fourn Er
fifty six point two. I'm going to drop the point two and it's gonna
be fourn Er fifty six, and I'm gonna size my conductor accordingly. Right,
So this is sizing the neutral for the service. Keep this in mind
that if you're doing a brand circuit and you get a question on an exam
that wants to know what the actual contribution is for the neutral, then all
you're gonna answer that is by giving the exact value, not rounding it.
Just the exact value. Here we're talking about a service calculation, so we're
going to be rounding and those type of things again. But just keep that
in mind. If you want to use the total value, that's that's fine.
But in this case, since it was less than point five, then
we're gonna we dropped it off, so that was four or fifty six.
So size your neutral conductor accordingly. Again, can't be smaller than what's given
in two fifty one zero two c one, but in this case it's obviously
going to be larger. So we're okay there. Now, what if I
ask you this question. We'll use the same amp values, but now I
tell you that two hundred amps of that six ninety I'm excuse me, two
hundred amps. So that five to sixty six is non linear loads. Now,
remember prohibited in two twenty sixty one C says that that portion of it
of the neutral that is non linear, you cannot apply the seventy percent to
it. Okay, So that tells us that we just got to exclude that
from the equation. So let's do it. So the same values five hundred
and sixty six amps of our calculated what we've calculated out to be our neutral
loads. And so I'm going to take that five sixty six. I'm gonna
subtract away two hundred because we know the first two hundred has to be one
hundred percent anyway, So that's two hundred. So we're just gonna put that
aside. And so we do that, and what does that leave us?
Okay, So we take the five six six minus two hundred, that equals
three hundred and sixty six. Now, remember what we said, two hundred
of that five sixty six is also non linear loads. So we're gonna take
away two hundred from this three sixty six as well. So we're gonna take
two hundred away from that. That leaves us with one sixty six of load
neutral load that we can now apply the seventy percent. To remember, the
first two hundred one hundred percent got to take the full two hundred the amount
over that you can apply the seventy percent. But remember we cannot apply it
to those non linear loads. So what we've got is, let's recap.
We have five sixty six minus two hundred. That's the first two hundred minus
another two hundred for those non linear loads. So we were taking into consideration
that gave us one sixty six. We multiply that by seventy percent. That
gives us one hundred and sixteen point two. You can drop the point two
if you choose at this point, or carry it on and go on through
the math. But now I've got to add back the two hundred of the
original two hundred, and I have to add that two hundred back of that
non linear load that we couldn't reduce. So it's one sixteen point two plus
two hundred plus two hundred equals five hundred and sixteen point two. I can
drop the point two if you would like, and that is five hundred and
sixteen amps of now neutral load. And again that point two is the actual
value. It's not going to change the value at the end of the day.
Okay, so you're going to size the conductors accordingly to handle that maximum
and balanced load. After we've applied what we could do a reduction on and
also what we could not do a reduction on. And so that's exactly how
we work that entirely based on those two given examples. Okay, all right,
folks, hopefully got something out of that. Those are kind of two
examples and it kind of mixes with the whole lesson that we did today.
Hopefully that answers the gentleman's question on derating the neutral when you can, when
you can't, and then how you would apply it if you have both nonlinear
and you have linear loads and a calculation what you reduce the neutral buy and
how you use these different rules and it's a little clearer for you. Again,
if you want to learn more about the National Eletrical Code, we encourage
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God bless and keep learning. Both ask both as both ask no f