why is it that we bond our neutrals and grounds at
the service panel but we don't do it at the sub panels that are say
in the garage or somewhere else in the house this is really important actually so stay tuned
what's going on my friends dustin stelzner with electricianu this was a question that
was sent in to me from youtube it says "mr stelzer hello i'm a big fan thanks for putting
out excellent content can you please make a video explaining why the secondary breaker box
meaning a sub panel not the main service panel why the secondary breaker box the one in my garage in
the house is not bonded between the neutral and ground it is fed by a double 50 amp breaker in
my 200 amp service and the bonding occurs there my ibew buddy swears i did it incorrectly but i
got my understanding from something in one of your videos this is from darren eckler" on youtube so
Darren let's get into this on the whiteboard now before we get started make sure you get your ucrew
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check out the link below electricianu.com all right so this whole issue of why we bond at the
service panel we bring our uh our neutrals and our grounds together let me draw the bond uh
i'll just go like this so that you know that they're bonded together
this is what we do at a service panel we make sure all of the neutrals and all the grounds all of the
grounded conductors and all of the grounding conductors are all bonded together at a single
point that is connected to earth now they're connected to earth that's a different thing
than just bonding them together what we're doing is making sure that everything that's grounded
in a structure does not have current on it you know our ground our equipment grounding conductor
should not have current on it but in a fault in a ground fault situation where maybe one of these
hots like slips off its termination and hits the the metal casing when somebody goes up and walk
and touches that metal of that dryer in this case they don't get shocked there's not current on that
ground but that ground needs to make a completed circuit all the way back to the transformer
up at the pole for the breaker to trip if it doesn't if it doesn't have a complete circuit
it's not going to trip a breaker you're just going to have something that's potentially energized
and it's a hazard and somebody can get shocked or electrocuted and there is a difference for those
who didn't know electrocution normally means death and getting shocked just means getting shocked
all right so uh what we have in this situation we have a service panel outside we've got a sub
panel and a garage the sub panel is going to be fed off of a breaker so we've got a 220 breaker
that's feeding over to feed our panel with it we carry an equipment grounding conductor
and then we have a neutral or a grounded conductor in code so we run all of these over to a new panel
from here in the sub panel let's say that we've got a dryer and we read 220 or this dryer we
also ran a neutral with it and a ground with it it's a four prong modern fancy dryer the reason
that we need to keep everything separated is a concept called objectionable current so it means
objection there's a problem there's something wrong there's like we need to address something
objectionable current is when there is current on something and there shouldn't be current
on something or more specifically there's current in two different places going in two
different directions where it should not be now objectionable current would be if we had current
uh and in a fault condition where uh anytime we have a fault we want to be
very precise about where we're allowing current to flow we don't want it to just kind of go wherever
the hell it wants to go because we could fry other equipment there's a lot of things that
could happen people could get shocked for some reason you're standing on something metal in
a shower you get shocked so we want to make sure that we control where current is flowing
so we definitely don't want this ground conductor to act as a neutral we don't want it to carry
current all the time neutrals are designed to carry current and grounds are not so if we have a
objectionable current on a ground when we're supposed to have current on a neutral we could
have it going down both paths so essentially if we didn't bond our neutral and our ground together we
could have current flowing on the neutral and on the ground at the same time both trying to get
back to source and finding whatever means they needed to you'd have parallel paths of current
so we always want to try to minimize that we want one guaranteed where fault current can go to
to get back to source so if we have a situation where a fault happens ground fault specifically
not a short circuit a lot of people misuse this terminology a short circuit is when you have a
circuit that has a shortcut in it basically it's not it has nothing to do with ground it's either
hot to neutral or hot to hot a ground fault is specifically when you have a hot conductor
touching your equipment grounding conductor or touching ground they call it a ground fault so
a ground fault and a short circuit two different things so say in this situation we have a ground
fault let's figure out where the current is going to travel say that this red conductor
for some reason contacts the case our ground is contacting the case as well so now we have current
that is going from this breaker through the case through the equipment grounding conductor going
all the way back over here and since it's bonded to neutral it has a path and it has a completed
path all the way up to the transformer so that will cause current to flow momentarily it'll cause
so much current because there's no load in between this red and this green anymore for electricity to
really operate there has to be a load in between it so as currents flowing there's something that's
resisting or that's impeding that current flow and that makes electricity travel at kind of a
responsible rate enough for us to use it if there's no resistance to that current flow
it's going to go unimpeded very very fast things are going to get really hot it's going to become
chaotic very very quickly you're going to have insulation melting off the conductors you might
even liquefy the conductors and completely melt the conductors themselves depending
on the situation the heat and available fault current and all of that so you need impedance
right you need something impeding the circuit for it to do meaningful work well in this case
we have a hot that's touching the case there's no resistance at all there's nothing impeding it
so that current's gonna go flying through the circuit so we have a complete circuit i should
probably have drawn this red also so on the red from our transformer up here we've got like the
start of the circuit travels down through the reds all the way over here back all the way through the
ground and that ground because the ground and the neutral are bonded that it's going to travel that
current is going to travel back up on the neutral which is going to allow and complete circuit for
the entirety of that circuit to be complete so current will flow so much of it will flow that
this breaker right here is going to trip because that's what the breaker breaker's supposed to do
if we did not bond this uh how do i do this if we did not bond the neutral in the
ground then this fault would occur but current wouldn't travel because we don't have a complete
loop anywhere so we just have all of this metal enclosure this entire metal conductor uh the metal
inside this panel the metal that the panel is hooked up to this conductor ground rod everything
metal all along the way will have potential on it so if you touch this and you were to say
touch a neutral or touch anything else that's at a different potential current would flow through you
as a way to try to get back to the source where it's always trying to get to so nothing would
actually happen it wouldn't clear a breaker this fault would happen all of this stuff would have
potential on it doesn't necessarily mean it would be energized but would it would have potential
available depending on if you touched from one potential to another potential to create a
difference of potential or a voltage for pressure to push current through you so it's a dangerous
situation if we don't bond these together and we're never gonna get the breaker to trip
if we don't bond them the neutral is our path back to source and that's how we have a completed loop
um in a transformer uh say we have our pole that has a huge transformer out here we've got
the utility company with its smoke stacks and a big generator in here and we've got a house
so we actually have two completed circuits when we talk about uh utility there might be more than
that because distribution it changes from voltage you know different multiple different times but
what we have is we have a primary circuit that comes from a generator so it means we have
one conductor that goes all the way out in the field brings power out to a transformer
that's up on a pole it's one piece of wire unbroken the entire time it comes back out
goes back to the generator where it is also another loop we have one continuous circuit
coming from the utility company to the power pole that's out at your house that's a complete
circuit that's how current flows then we have a secondary circuit i'll do that a different color
what we times call the secondary out in the field if you hear somebody saying oh the
primary or the secondary they're talking about on a transformer so we've got our secondary
circuit and the secondary comes down we have our black
we have our red
we still don't have a completed circuit right when we land these conductors inside the panel
we're breaking the circuit there's no completion to them so what we do is we run all these circuits
out from the panel to loads and from here this breaker is going to touch the black it's going
to go out to our washing machine it's going to hook up to the washing machine inside the washing
machine there's going to be another a motor so basically another coil kind of like this
and then we're going to have our red conductor that we bring from a breaker you know on the red
phase and we go straight out to that so when we flip a switch like say the say there's a switch on
one of these you know the the washing machine or the dryer is off and we push a button to start it
we close a switch and we connect this load so now we have current in a complete loop traveling and
that's why that washer or that dryer is on you shut it off it opens the circuit and it no longer
has current moving through it so it has to have a completed circuit somehow to travel the neutral
and if i didn't state this enough the neutral point is always going to be the middle point in
the system so we have a neutral that we run to the transformer as well that is how this green
that's connected to the case of this that's connected to the case of this that's connected
to the ground rod again ground doesn't ground rod doesn't have anything to do with tripping a
breaker it's there for a different reason but that means if we're bonding our all of our metal stuff
to our neutral then anytime we have current that goes from one of the hots to any pieces
of metal around electrical equipment now it has a complete loop it has a complete loop on neutral
through red all the way around that's how we get that breaker to trip if we did not bond
those things it would not happen we wouldn't have a breaker that trips we would just have
a whole bunch of metal that has potential on it to hurt or kill somebody because it's energized
or it's waiting to be energized because there's potential on it there's a voltage that is
uh available on it that's why we on the secondary panels or the subpanels we never bond and that
means if you have like 50 panels in a house which i don't know why you would but if you
had 50 panels you would not bond the neutral to ground on any of them at all the only place
you want to bond is at that service panel now the reason for this if you sit and think about it it
actually kind of makes sense so i drew basically a service and then all of these are sub panels
so say this is like at one end of the house this is another end of the house this is
at like on the other end of the house somewhere each one of the panels feeds another panel right
so we've got a completed loop all the way from the service all the way through red all the way
to our piece of equipment we've got you know neutral that's the same thing goes all the way
from the service all the way through neutral so essentially red and neutral have a complete loop
here inside of the piece of equipment let me just draw uh we'll say like there's a winding in there
so you can see right this is a closed loop it goes all the way through and all the way back
but the ground you'll notice is a completely separate thing it's not trying to form a loop
for current to go through a breaker and be a part of the the system all it's trying to do
is bond all of the metal things together and go back and reference to ground and reference to
neutral at this one point so this is the point where we put a bonding jumper in at the service
so if we have a short circuit let's say or a ground fault sorry say this red conductor
for some reason just flops off and like boom hits the case well we have a path so
now we know that we are going through this red all the way through this entire thing
and then we have a path on ground all the way back to neutral to go back up to the service
to form our complete loop so that is a complete circle i know it's kind of like drawn crazy
but it is it's a complete it's a complete loop if that bonding jumper was gone and that ground fault
happened there would be no way for this breaker to trip it would just stay in an energized state
because there is no complete loop to make the breaker trip now objectionable current what that
speaks to is say we have a ground fault and on every one of these panels i'm just going to draw
a quick bonding jumper we have bonding jumpers so that every single neutral and every single ground
are bonded at every single place what that what happens is in a ground fault like that situation
now we have two paths that that current could take at the same time going through the system
and that's what we don't want so current could take this path and go all the way through
and could make it back up to the panel right that's okay but now that our grounds and neutrals
are bonded it can also take the path through neutral the entire way and end up back at the
service so now we have two parallel paths that current can take and we don't want that that's
an irresponsible thing to do we want to make sure that it goes through one singular path only
reason being uh if there's any loads on any of these panels which there will be there's
breakers everywhere but there's gonna be loads and say we've got laptops and tvs and all these things
hooked up well they're all hooked up to that neutral so we don't want a ground fault to go
through equipment as well as go through the ground that's the entire reason that we have a ground
is for this purpose to direct that fault current elsewhere now say we have a short circuit instead
of a ground fault say instead of this conductor uh you know flopped off and hit the case and it was a
ground fault meaning the hot is touching ground say we have a short circuit so uh now we've got
like a black and a white that are touching together well instead of just clearing the
fault in the black and white now we've got bonds from neutral from the white to the green the
neutral to the ground everywhere so now that short circuit current is traveling on all of this metal
stuff and that's an objectionable path because the short circuit should be taken care of through
a breaker through that hot and that neutral it should be one complete loop we shouldn't introduce
metal parts to that short circuit because a short circuit is a very different thing it's it's
still a fault but it's not a ground fault so in either case you're providing two
different paths for current to take which means it could go anywhere that it wants to take it
could go on everything metal but it could also go through every piece of equipment and you know
anything that you have wired in this this entire place and so it could start frying equipment and
things like that so it's really it's silly you don't want to bond anything anywhere but the
one place you do want to bond everything is back here at the service because it's the only way that
ground fault current can make it to the neutral and actually complete a circuit and the only
way a breaker trips is if there is a completed circuit for that current to keep traveling through
if there's not a complete circuit no current travels so we just have this potential over
here on everything metal and anything that touches between two points current is going to go through
it so that's the hazard of it so i hope that that makes a little bit more sense we just do not want
two different parallel paths we want one path for fault current to take and we want to connect
it back and bond it right here so that that current goes along the ground and back up to the
the utility up to the transformer and clears that fault actually opens that breaker grounding and
bonding is kind of a crazy thing there's a whole bunch of other different situations if you have
a you know transformer or you know whether or not you have a generator how it needs to be grounded
whether or not you have a floating neutral a lot of different things to consider so grounding and
bonding which is article 250 and code is a really heavily talked about topic but as an
electrician i think that's a good place to start diving in and trying to figure some of this stuff
out because it's actually very very important grounding has a lot to do with life safety and
people not getting injured or hurt equipment not getting destroyed so it's very important
to know about that kind of stuff so that was a great question thank you so much for your time
i love you crazy people put more comments below i'll make more videos like these talk to you soon
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