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Speaker 2: Everybody? Welcome to another episode of Mastering UNEC. My name
is Paul Labernathy. Thank you for joining me on today's podcast.
So on today's podcast, we're going to talk about voltage
drop a little bit. There's been a lot of discussion
about voltage drop on social media. Obviously, people have been
talking about voltage drop for years. People do questions about
voltage drop. It appears on electric exams educators, we teach
the formula for a voltage drop, and so I figured
i'd talk a little bit about it because we also
get many people who who think that voltage drop in residential,
for example, is a requirement, and for residential it's never
a requirement. First of all, the only two locations within
the National Electrical Code first that we'll talk about is
when we have to require voltage drop for sensitive electronic equipment.
So that's that would be the first application. So if
you're dealing with sensitive electronic equipment, then you're going to
have a requirement to deal with that, you know. So
in if you've had your codebook, and I know you do,
if you probably have it handy, that be articles six
forty seven, and in six forty seven you're going to
see that there's a voltage drop requirement under six forty
seven dot four D. Now that talks about the vaulted
drop on any brand circuit not to exceed one point
five percent, and then the combined voltage drop of a
feeder in brand circuit conductors shall not exceed two point
five percent. That is only having to do with sensitive
electronic equipment. Now, unlike electrical distribution systems that you know
supply the lighting and the appliances and those type of
brand circuits. That's different because here in six forty seven
the vultage drop requirement is mandatory, and those other areas
of the code that we're going to look at under
two ten dot nineteen, for example, is not a mandatory rule.
It may be good design, but it's not mandatory. However,
the rules for sensitive electronic equipment in six forty seven
dot four D that is a requirement if you're dealing
with it. So if you have an application where you're
dealing with sensitive electronic equipment, the scope of that is
this article covers the installation and wiring of separately durized
systems operating at one hundred and twenty volts line to
line and sixty volts to ground for sensitive electronic equipment.
That's what this scope is an article six forty seven.
If that's what you've got, then you have a mandatory
sensitive electronic equipment. You have a mandatory voltage drop requirement. Now,
the only other mandatory requirement for voltage drop is y'all
all are probably aware of this when it comes to
fire pumps, and that's six ninety five dot seven, and
that is a little different in that one it's talking
about Like from motor starting. It says, unless specify the
six ninety five dot seven B or C are met,
the voltage at the fire pump controller line terminal shall
not drop more than fifteen percent below the normal controller
rated voltage under motor starting conditions. So start the motor.
You have them the actual voltage rating that's stamped on
the controller. You're falling within that range. You immediately try
to start the fire pump and the voltage cannot drop
below fifteen percent below that normal controller rated voltage. Okay,
now where do we get that? That information actually is
extracted straight out of NFPA twenty under Section nine Subdivision
four point one. So it comes out of NFPA twenty
and gets regurgitated over here into fire pumps for voltage drop. Now,
that's for starting motors. When it's motors running, then you
have another requirement, and that one says the voltage at
the contactor load terminals to which the motor is connected
shall not drop more than five percent below the voltage
rating of the motor when the motor is operating at
one hundred and fifteen percent of the full low current
rating of the motor. That also comes out of NFPA
twenty and that is nine point four point four. So
those anyway, those are the two locations where and you
really as an electrician, I mean, that's not going to
be residential. None of that's going to be residential. It's
always going to be commercial for that stuff. And then
of course most of the time when you're dealing with
the fire pump or even sense of electronic equipment, you
got some kind of engineering design involved, and you're hoping
that they have already taken all this into consideration in
their design. You hope that should not be my responsibility
as the electric trition if I'm just installing it, I'm
not designing the system, okay, But again it's it behooves
the electrician to fully understand how that works so that
you can kind of be another set of eyes on
the situation in case somebody dropped the ball somewhere. Now,
if we talk just residential, the only time that voltage
drop will creep into a discussion in residential applications. Is
when we're looking at two ten dot nineteen, and it's
an informational note that's under the minimum mapacity and size
of a conductor. And the informational note says conductors for
brand circuits as defined an Article one hundred size to
prevent a voltage drop exceeding three percent at the farthest
outlet of power, heating and lighting loads or a combination
of such loads, and where the maximum total vaultage drop
on both the feet and the brand circuits to the
farthest outlet does not exceed five percent five percent, And
that says provides reasonable efficiency of operation, okay. And it also,
by the way, says exact same thing in two fifteen
dot two A two. So for brand circuits, I mean
for feeder circuits. Now, the thing about this is this
is under an informational note, so it's just really good information.
At no point in a residential application are you going
to be required to meet this stuff. And if a
jurisdiction tries to push this on you, you got to
remind them that informational notes are not enforceable, and they go, well,
it's enforceable in my jurisdiction. Well, then you've got to
push back, right, because you have to push back and
have them understand the rules. And the rules are all
given to us in Article ninety right, and it makes
it clear under ninety dot three, which is the code arrangement,
lets us know that chapters one through four applied generally
throughout all all electrical installations. And of course you got five, six,
and seven, which supplement or monifi chapters one through seven.
Then of course you got eight which is standalone communications.
And of course you have chapter nine, which is applicable
when it's referenced. And of course the informative annexes are
just information, just like an informational note. They're just there
for good information, like INFORMI of NXC when it comes
to raceway PHIL. Okay, that's just good information. You can
get there by actually doing the calculation, but the information
the informative ANXC kind of gets you there. And it's
based on the forty percent PHIL for over two conductors,
so you get there that way. But kind of how
the structure goes now, but if you look at the
beginning of ninety dyed three, it'll tell you it says
informative anxes are not part of the requirements for the code,
but are included for informational purposes right now. To find
out where the informational note comes in, then we have
to look at ninety DIED five, which talks about mandatory rules,
permissive rules, and explanatory material and item number C is
explanatory material, and it makes it very clear that it
says explanatory materials such as references to other standards like
we talked about inn FPA twenty for the fire pumps
and things like that. It says references to other standards,
references to related sections of this code, or information related
to a code rule is included in this code in
the form of an informational note or an informative annex
like we just talked about. Okay, so they are not enforceable,
because it goes on to say such notes are informational
only and are not enforceable as requirements of this code.
They may be great information, and they may give you
a lot of guidance in how you work through the
NEC and maybe it kind of reminds you of a
certain place you need to be, But at the end
of the day, that's all it is. It's just information,
great information to help guide you a little bit, but
it's not enforceable, so they can't enforce voltage drop on
you in a residential application at all. Now, is it
a good design practice, Yes, is, but there's really not
much in a residence, be honest with you that's going
to really push a voltage drop issue. Now I've done
multi Here's where I do have a problem. I have
seen and I have been on the case of a
very large home in Oklahoma, and when you start having
voltage drop, although it's not requirement in the code, but
you have really really long runs because let's say they
designed it, in my opinion, poorly, instead of having some
remote distribution panels or some people like to say subpanels
positioned around the large dwelling, then you could have a
twelve to two or fourteen two that literally run two
hundred and fifty feet before it gets to one part
of the dwelling. I've seen it. I've just recently was
on a case in Oklahoma about this, and I served
as expert witness for it where you had circuits acting up,
causing AFCI devices to trip and without even having any
loads on it, there was no case to neutral connections.
It's just I believe, and again this is just my
belief because I didn't test it, but I believe that
voltage drop in distance could have a problem with some
of these devices. I can't quantify that. I can't tell
you I've done the testing for that. But how I
can kind of get there is when I go look
at two ten, dot twelve, and I look at the
different locations, and then I go down and I look at, Okay,
what are the options, the six options that I have.
If you look at two of the options, it's limiting
the conductors. If it's fourteen, gag, it's limited to fifty feet,
If it's twelve, it's limiting it to seventy I get it.
These are listed supplemental ARC protective circuit breakers in conjunction
with a outlet style AFCI. But you see what I'm saying.
There seems to be some limitation here on the length.
And then when you get down the same thing happens
if you have a listed outlet branch circuit type AFCI
installed on a brand circuit at the first outlet point,
and you use it with a listed brand circuit OVERCURP
protected device so that basically they have to be evaluated
as a combination. Okay, you just can't take a regular
circuit breaker and just pick a REGULARFCI receptacle device and
consider them a combination. No, they would have to be
evaluated together. But my point is if you look at
the rules there for this, you'll see that there is
linked limitations. They're limiting the length of these conductors of
fourteen gage in twelve gage. So I am a bit
dubious of this. So you know, I have asked manufacturers
of afci's, I've emailed them, I have people I know
I asked them, and I'm saying, look in your code.
I'm in the code. It does not give a lenth
limitation on AFCI devices. How far can I run that
brand circuit before I run a potential for voltage drop?
And will it affect the afci's operation. If the answer
to that is no, then answer me why we have
a limitation on the other ones? Okay, why do we
have a limitation on two ten, dot twelve, A three
and A four? Why are we limited in those but
we're not limited in the other I don't know. I
just a hypothesis I have. My point is this. There's
nothing right now in the National Electrical Code or even
the IECC Energy Conservation Code. There is nothing in there
specifically for residential application that would be something that you
can sink your teeth into to say, you know what,
voltage drop needs to be taken into consideration, all right,
other than the fact that it's just made an informational
note that's recommending it, that's it. But that changes, folks
when you get to other than residential, And that's kind
of weird for people because they're like, all right, so
anywhere else in the code other than single family dwellings
and things like that, then we have other provisions that
are going to kick in and require voltage drop to
be a consideration. So if you happen to have a copy,
you may or may not. It's actually free. You can
go online and look at a digital version free of
the International Conservation Code. So I'm looking at the twenty
twenty one i eat CC, the June twenty fourth edition,
and I'm looking at it, and one of the things
that you have to take into consideration is that when
you look at it, there is a specific section in
here that is labeled voltage drop. Remember, this is an
Energy Conservation Code. So if the i ECC is adopted
in your area and they are utilizing it and that
type of thing, then you have to be aware of
the voltage drop requirement. That's in C four zero five
dot ten and it says voltage drop. And here's what
it says. It says the total vaultage drop across the
combination of customer owned service conductors, feeder conductors and branch
circuit conductors shall not exceed five percent. Okay, so the
vultage drop. So whether you're dealing with feeder, you're dealing
with service, or you're dealing with the brand circuit, what
you're dealing with is the total overall voltage drop across
the combination of those cannot be more than five percent. Now,
that's in the IECC, So that's gonna apply to where
that's gonna apply to commercial because that's under the commercial
portion of the IECC. There is nothing like this under
the residential portion. There is under the commercial at least
I'm not aware of anything under the residential and I've
looked at it. So with that in mind, if you
think about it, if they're enforcing the ie C C
in your jurisdiction, and it may be that the building
building inspector is the one that's enforcing this. They're not
really savvy and understanding voltage drop, right, they don't understand it.
They don't understand electrical unless they're a combination guy a gal.
So at the end of the day, there's a good
probability that in a commercial building that they don't even
understand that C four zero five dot ten is even here.
That's a voltage drop requirements in place. And you notice
it doesn't say anything about three percent. It's in overall
five okay, so anything you know. It's basically says the
total voltage drop across the combination of customer owned service conductors,
feeder conductors and brand circuit conductors shall not exceed five percent. Okay,
So we can't have a five percent from the beginning
all the way from the service through the feeder due
to the brand circuit, all the way to the end load.
We cannot have exceed five percent under the Energy Conservation
Code okay International IECC. So if you do have that,
go look at it. The two thousand and one, the
latest edition. Go look at C four zero five dot ten.
It's entitled I shouldn't see entitled. It's titled. It's entitled.
It's titled voltage drop, and it's in there. And if
this is an adopted application, then guess what it speaks to.
Requiring voltage drop is what it is. So while it
doesn't apply to residential, it's a good recommendation when it
comes to commercial applications very much does require that you
meet voltage drop applications. Okay, And again, this is a
commercial so it would be a building that falls underneath
the scope of being a commercial building. So this could
be where it doesn't apply to the individual dwelling units
of a multi family building, but it may apply to
the general application of the whole building, which is a
commercial aspect of it. It's going to be really what
your jurisdiction is enforcing and how they are enforcing it.
But it is in there. Now, is considering voltage drop
something that people should take into consideration. I believe they should,
even whether it's residential. We have to be good stewards
of the power. We have to be good stewards of
the fact that equipment is now getting more and more
sensitive to operate during a certain voltage range, and there's
a certain range that's optimized for equipment, and if it
hasn't voltage stamped on the equipment, then as a range,
typically you can go ten percent below or above. But again,
the equipment offers a range, and as long as you're
in that range then you'd be fine. But since voltage
drop is not a requirement anyway, for example, in a residential,
so you can say I like it within ten percent,
I like it within five percent of the vota. That's
up to you because there's no mandate for it now.
At some point when voltage drop, if it ever does
become a requirement in the National Electrical Code for other
than sensitive electronic equipment or fire pumps, then we're gonna
have to break it down and explain why. And so
a lot of people say, well, shouldn't it be that
way for motors, because if you don't give a motor
the right voltage, it can overheat prematurely. Yes, but motors
typically have an overload on it, and so that should
kick in. Now, that doesn't mean it's going to be efficient,
That doesn't mean that it's not gonna prematurely heat up
the motor in order to cause it to trip the overload. Yes,
it might will be that way when you don't have
voltages within the operating range of the equipment like the motor.
I get it. The question is is it become a
performance issue or a safety hazard. It's not a safety
hazard if it have overloads in place, although you prematurely
are going to be replacing motors that burn up because
again they're operating outside of their voltage range, so they
won't operate as efficiently and so they'll overheat longer, stay heated,
so the windings, everything might break down prematurely. It's not
gonna maybe not trip the overload, but it's going to
prematurely wear out the motor. And so you know, the
NEC is not a design manual, it's not a performance
based manual. Everything needs to be energy efficient. It's not
really that it's a safety standard. And so it's going
to be hard to get something in the National Electrical
Code to mandate voltage drop in areas where where currently
it's it's not at right now, which is the brand, circuit,
the feeder and the service. Now, the reason it's important
for fire pumps is obviously, as we said earlier, fire
pump needs to operate within its voltage range. We don't
need to premature surely overheat, and since it's generally dealing
with short circuit and ground fault protection and overload is
looked not considered because we do want the fire pump
to burn up, right, we want to get people out
of the building, so we don't want it to prematurely trip.
So that is why they want to make sure they
have enough voltage there so that doesn't prematurely cause the
motor to overheat. Well, that seems like that would also
apply to all other motors, but that one is a
little more safety driven because again, we want to make
sure that we can get people out of a building,
so we want to make sure that that's you know,
we're not going to have an issue of it overheating
because of a voltage issue, not getting enough voltage and
not working within the parameters of that motor. I get it.
You know, we has a whole different use now when
it comes to sense of electronic equipment. Again, it again
it depends on the type of equipment and they're very
sensitive and you know, they may be operating sensitive equipment
that is vital to the infrastructure. And so that code
panel with that submission to six forty seven have made
the determination on voltage drop and we just have to
honor it. It is what it is anywhere else in
the code. It's just right now. A good recommendation that
I think you should follow. Is it less important and
residential to me as it is in obviously commercial, but
it's still important nonetheless. So everybody needs to learn how
to do voltage drop calculations. To tom K time by
time's l divided by a circular mill or the percentage
depending on what you're trying to find, the conductor or
the circular mill, depending on what you're plugging in there.
If it's three phase, you substitute the two for one
point seventy three two. It's pretty basic voltage drop calculations,
and we teach this stuff in our courses in videos
that I do, but you need to understand how to
do it. And it's all very load dependent. You know,
voltage drop is very load dependent. You have to know
to do a voltage drop calculation properly. You have to
know what's what the load is. If you've got no load,
then there's no voltage drop. Because there's there's no load,
the circuit's not going to be complete. It's just sitting there.
So voltage drop is pointless if you're not pulling a
load at the end. I mean, it's pointless. So when
we do voltage drop calculations, we have to assume a
certain load. And like, if I'm doing it and I'm
just assuming it's a twenty amp circuit, then I'm going
to assume twenty amps at the end of that load
because I could pull twenty amps. So that's what I'm
figuring in. And when somebody asks me to do a
voltage drop calculation, whether it's with the Encore, Prismium, whoever
it is that people contact me, I always say, all right,
I need to know the distance one way, Okay, the
k we already can figure out. We already got that.
You know whether it's twenty one point two or twelve
point nine depending on whether using copper or aluminum. We
got that. We can use a two for single phase
one point seventy three to two for three phase. We
got that. But I have to know what is the
load at the end, what are the amps, what's being drawn,
because that's going to be a direct impactor on the
voltage drop.
Speaker 1: Uh.
Speaker 2: And so it's important that we have all that information.
So if I'm doing voltage drop and I'm making a
consideration for voltice drop, and I got to look at
the circuit. Now, I'm going to assume a full circuit
unless you state otherwise. Now I do have people that
contact me that says, hey, Paul, I'm going to run
this this load at the end of three hundred and
fifty feet and I'm like, okay, Well, the first thing
you do is you have to size the circuit to
protect the conductors. You have to size it. So if
it is a twenty amp circuit and you have twelve
gauge conductors, that's where you start. When it comes to
voltage drop, you start, you know the conductor you're running
to handle the load, always do it to handle the load.
And then you're protecting conductor with the overcurve protected device,
and you size it like you normally would, and then
you look at voltage drop because at the end of
the day, you still have to protect the conductor at
its opacities, right and that type of thing. So you
have to do those things. But the voltage drop aspect
of it is something that we look at after we
already know that we've got the circuit taken care of,
so as I know, I've got the right conductor and
everything taken care of. At that point, I may have
to increase the size of the conductors because of voltage drop,
but I'm not doing it because of the load. The
load is the load, Okay, I've already figured that in
to the equation. So I think a lot of people
get that wrong and they don't understand the concepts of
voltage drop. First things first, make sure you take take
care of the load. Make sure you size conductors everything
to handle the load first, to get that out of
the way. Once that's out of the way, if you're
going to take voltag drop into consideration, then and only
then do you start introducing the conductor sizes and the
percentages and start seeing whether that conductor is adequate enough.
If it's not, you may have to bump up the conductor.
It's still gonna be fine. And can I have a
larger conductor on an overcurrent device. That's say to have
a ten gauge and have it on a twenty eight device.
As long as the device can handle it, take it,
that's fine, that's not a problem. Could I splice from
that ten gauge back down to twelve to go to
a breaker on the one end and then splice it
to go back down to the other end. Absolutely, I could,
because we're doing it accommodate voltage drop. Well, I have
to increase the size of the equipment grounded conductor proportional
to the increased size of ungrounded conductors do to voltas drop. Absolutely,
and that's pretty straightforward. We cover all that two fifty
one twenty two B. It's a pretty easy process to
do that. We talk about all that in two fifty
one twenty two. So I mean, I think at the
end of the day, you have to take voltage drop
into consideration, even though the National Electrical Code is not
gonna mandate it on residential you know, keeping in mind
that the typical home is not gonna make a difference.
I would go out on the limb and say, any
home that is four thousand square feet or less, it
is not gonna make a difference. It really isn't. Now
you start getting those ten thousand square foot twelve fifteen
thousand square foot homes and you don't think about how
you locate the panels. Again, it just makes sense to
locate some panels centrally so I don't have to run
these long home runs. Why because they could be damaged
when the building finishes, going up the gypsum board, the trim,
the moll damn. If I want to have some long
home run stuck somewhere in the walls that I don't
know where it could be nailed through, I'd much rather
have a feeder, one cable that I can be very
paranoid about how I run it to a panel that's
centrally located to feed loads at that end. It reduces
the vaultage drop right, but it also reduces the issues
of these long home runs. I only have one long
home run, you get what I'm saying. So it's all
about design. And I think people today, like I saw
in that Oklahoma house, why in the world that electrician
would run home runs on that big ass house. I mean,
I'm talking big house, folks, I'm talking eight car ten
car garage. I'm talking It's just an amazing house, beautiful house.
But it had issues with afciyes in it because I
believe the circuits were the home runs were too long.
Plus there was other things that they had to cut
sheet rocked out because of nails too. Look it's because
they ran these fricking twelve twos and fourteen twos and whatnot,
three hundred and fifty damn feet to get back to
a panel two hundred and fifty feet things like that,
and I just think that it could have been designed
much better. But that's me. That's just a design that's
the design guy in me. I just think they got
a poor installation. So do I want to do the
the investigation on the afcis whatever? No, I don't unless
they want to pay me to do it. And that
wasn't what they hired me for. That was you know,
that's just something that I put out there to the
manufacturers and I go, you know, I'm going to ask
you all a question. What is the maximum distance you
can run with an AFCI and not potentially have issues?
Is voltage drop ever an issue with these devices? Is that?
Can that play a role? Why do you limit it
to fifty and seventy feet under to ten dot twelve?
But not for a combination. You know, we're looking for
series and parallels, you know there you're looking at You're
not worried about distance on those, but is there a
potential distance issue that we need to be aware of,
so I don't know. I can't answer that for them.
You know, that's the those manufacturers have to answer that question.
And I haven't seen that answered anywhere. So AnyWho. All right, guys, anyway,
that's kind of a little discussion on my thoughts on
voltage drop and again energy. The International Energy Conservation Code
seems to demand it right when it comes to commercial,
doesn't really say anything when it's residential. The any C
only requires it for sensitive electronic equipment and fire pump applications,
where it is mandatory everywhere else, it's just really good information.
A design professional, I would always take voltage drop into
consideration just to make sure that I'm making sure that
everything works within its voltage range. I don't want premature
things like motors and air conditioning units. I don't want
to have a Whirlpool hot tub. You know, I have
an issue with the motor being so long up at
a bedroom that's one hundred and ninety feet away, and
what is the voltage there? And and did I take
those loads into consideration? I get it in a real world,
we're just running cable and we don't really take those
things into account. But you know, it's not required for residential,
but move into commercial and then we already have a
requirement and see four zero five dot ten for voltas
drop in the International Energy Code. So the International Energy
Conservation Code. So does your jurisdiction enforce that? Is that
one of the adopted standards from your state that you know?
Maybe your your jurisdiction is choosing to look the other way.
Maybe they don't even know that volta's drop requirement is
in there. Maybe not, who knows. Anyway, there you go, folks,
Thanks for joining me. Hopefully you got something out of
today's episode. Join us next time for another Master to
the NEC podcast and we'll catch you hopefully in the
mornings on Coffee Hour. Join me eight am Monday through
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eight am Eastern time. Love to catch you there, bring
your questions, bring your insights, Love to chat with you
until next time, folks, Stay safe, God.
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