Why Do We Bond at the Service Panel and Not a Subpanel?

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 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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 Descant Music and Video.

Channel: Electrician U

Views: 517,344

Keywords: electrician, electrical, electricity, dustin stelzer, electrician vlog, construction, commercial, residential, electrical vlog, electrical courses, electrician courses, electrical class, electrician class, electrician school

Id: 6QEYg4wX70E

Length: 19min 45sec (1185 seconds)

Published: Wed Feb 16 2022