What is a Short? What Causes Them?

oftentimes when people are talking about electrical circuits they say the word short like oh this shorted out to that or oh it's a short it's a dead bolt short s actually means a very specific thing no no not that either kinda [Music] all right so I know I'm kind of being a stickler on this but I think it's really important to understand the language that we use because we're being descriptive of something happening so a short just means a short circuit right it normally we're supposed to have a circuit with two conductors that go to a load to some sort of resistance or impedance if we connect those wires before that resistance or an impedance it's taking a shortcut through the circuit so a short just kind of means a shortcut it means taking the load out of the equation so most things that happen most faults as we call them are shorts but when you're talking about what is going on in the circuit as an electrician you need to understand more than just short we have ground faults that means that there's a short to ground it's more accurately a fault so instead of just using the word short all the time I would use the word fault and if it's a ground fault you know there's a problem with ground if it's an arc fault you know that there's a arcing problem in the circuit or if it's a short you could say it's a short but you even want to go more in depth than that you want to know is it a 120 short is it a 240 short is it two thing too hot or you know ungrounded conductors touching each other so identifying the different types of shorts is better than just calling them all shorts but before we get into each one let's talk about Breakers make sure that you stay tuned till the end because at the end of the video I'm going to short some stuff out and do some 220 shorts some short circuits ground faults and actually show how they work [Music] you ever wondered what's going on inside of Breakers so let's take a look inside of here it looks really complex but essentially all that's happening is that there's a spring and you can attach to close a circuit or you can open a circuit so I'm going to put my fingers on this just so everything doesn't explode at me when I'm doing this but this isn't an off state right there's nothing connecting the bus here to the rest of the mechanics inside of this when we turn it on it closes so now current can go through all of this metal and out this back terminal and then we can shut it off and open it but what happens when a breaker trips so let's reset this we notice that this little orange piece is not in the window so that trip window actually will signify and when a trip happens this whole thing moves up to show the trip window so let's trip it you can see the little orange pops up in the trip window I'm gonna reset it Breakers actually trip by two different methods there's a thermal trip mechanism inside here which is a bi-metallic strip so if you have a little bit of overheating say this 20 amp breaker has like 24 amps on it we're just slowly building up too much heat after a while this bi-metallic strip is actually going to bend and that is what causes this whole thing to trip then when we have something that's a little bit more catastrophic like a short circuit there's going to be a lot more current flowing through than there would in just a thermal event so then we have a magnetic event inside of here so there's the thermal trip mechanism and there's a magnetic trip mechanism magnetic trip mechanism is designed at around 200 percent of whatever the breaker's rating is so a 20 amp breaker at about 40 amps it should magnetically separate these leads from each other so just like that so that is how Breakers work did you know that there actually was a point in our history where there was no ground conductor we just had Hots and neutrals or Hots and other Hots so the concept of grounding was introduced to very specific pieces of equipment in the 30s and 40s took a while for the adoption to actually kind of like carry through the rest of the nation but that was when the national electrical code started to require that we put grounds on things and it was at first just for specific pieces of equipment they wanted grounds uh or a conductor that could carry faults all the way back to a Transformer or a generator so that would carry fault current and it was a specifically different thing than a short circuit and then we had grounding electrodes and grounding Electro conductors that were introduced in the 60s so same kind of thing we wanted to make sure that we had a point of reference for the entire electrical system to Earth but they're both very different reasons why they were installed but this whole idea of shorts or short circuits pre-dated ground faults because grounds were not even a part of electrical systems until the mid 21st century now you know are you a super nerd electrician like me or are you like reading books and talking about Theory and all watching videos and stuff like that you should become a member of electricianu.com so membership has a few different benefits you get all practice exams that we make for free we've got a residential Wireman a juryman and a master we also have a thing called the code can which is 300 questions and it's not timed it's self-paced taken as many times as you want and for all of our members every single month we put out new premium content so a lot of videos like this that do not get put on YouTube they're just private for our members and then we have courses that we drop every month so every single month we have some new course it could be Transformers motors motor controls calculations all kinds of stuff but they're self-paced so you can kind of go through them whenever you want so if you're interested in nerding out like I do check out the link in the description below where it says membership and come join us oh thank you when a short circuit or a ground fault or an arc flash happens it's a really dangerous situation there's a couple of reasons why you can take something heated up to a certain amount and then it changes from solid to liquid if you have liquid like water you're boiling it you raise the temperature to 212 degrees and all of a sudden it starts turning into a vapor well with the short circuit you can actually take solid copper and turn it straight into a vapor it skips the boiling part and it skips the liquification part and turns straight into a vapor that's kind of nuts so to get this to happen you have to have solid copper you have to heat it up to a certain point so the boiling point of copper is like 9985 degrees and it'll start to liquefy but if you heat it up to an insane amount very quickly like 4 644 degrees Fahrenheit it will turn straight from a solid into a gas so when you short something out you notice a lot of the copper disappears it's like where did it just go it literally turned into vapor and just dissipated in the air so this is why it's really important when you're working on electrical circuits don't work live 95 of the time you don't need to but there are times when you're going to have to just make sure that you're wearing PPE wear hot gloves wear some safety glasses Klein's got some cool ones that look like snowboarding glasses that you're going to see here in a minute but make sure that you're wearing proper PPE in those very rare situations where you actually need to work live otherwise just don't risk it it's your life you only get one foreign just don't do it be safe out there so what happens if you're at a supply house and you're trying to get Breakers but you don't know what all the breakers are that they make do they make a 46 do they make a 53 there are standardized Breakers in our industry and it helps to know in code at table 240.6a there's actually a chart of all the standardized circuit breaker sizes but what happens if you're kind of like in between a size can you round up or should you use the one that's smaller if you use a breaker that's smaller than your load it might trip all the time if you use a breaker that's bigger than your load is that okay so there's actually another part in code 240.4b and C that talk about being able to round up to the next breaker size if you're up to 800 amps but once you get over 800 amps you cannot round up anymore now in order to round up there are things that you have to follow so make sure you read 240.4b there's a one two and three in all three of those conditions must be met [Music] thank you all right so let's look a little bit at the drawings of a circuit and how it all works because a lot of apprentices don't really conceptualize a whole circuit actually including the Transformer out of the property and that is where the circuit is completed for current to travel so from the Transformer out of the property we'll have a panel in the middle sure that'll all run through and then we'll have Breakers and it goes out to a box but just to like clean all of that up and not even talk about it let's look at this conceptually so we essentially just have a hot coming into a box and we have a neutral coming into a box right so nothing's going to cause a breaker to trip there's nothing touching anything that it's not supposed to touch but let's say that we have a short circuit so the White and the black touch each other what's going to happen is the breaker is going to open because there's going to be so much current flowing in this Loop that it's going to cause more current to flow through the breaker than that breaker is designed to handle so the breaker should trip at about 200 percent or more there could be way more current than that but it will trip because so much current is flowing through right that's how Breakers trip there's a lot of current so we're intentionally designing a device to break her to trip to remove something when there's a whole bunch of current flowing through it so that's a short circuit right it's a shortcut there's no load in between there to slow that current or minimize that current it has nothing to do with the ground if you notice the ground doesn't even go to the Transformer the grounds are usually just tapped to the neutral somewhere in the system and so when we have a ground fault what's happening is we've got this black conductor that somehow touches this metal box which completes the circuit to the ground which the grounding jumper or bonding jumper is touching the box also so that's how we get current to go through this neutral we've got the complete loop from our hot through the box through the green conductor the ground and back to neutral and so the rest of the point from that place at the service disconnect where the neutrals and the grounds bond together from the rest of the circuit back to the Transformer it's traveling on the white and that's how it gets its complete circuit that's how ground faults actually trip now we do have ground fault breakers that have a little bit more you know a little board inside of them and there's more going on with something like that but a ground fault breaker is just essentially there's an added level of protection that we want to give people if they're like standing in water or something we don't want a massive amount of current to have to flow through for a ground fault to trip a breaker we want to have a little bit more sensitive so a normal breaker with a ground fault will trip like this but a ground fault breaker is designed to sense really tiny imbalances in a circuit so it doesn't even get to the point where there's this much current flowing through it but that's a ground fault it's pretty much still just a short circuit it's just anything metal everywhere is all connected together so if at any point any energized can a conductor touches any piece of metal it all goes back to that green that's bonded at the service goes out to the white completes a circuit so that enough current will flow through that breaker to trip it now let's look at an arc fault we've got a series arc fault so a series arc fault same kind of thing is going to happen except the fault's not over here the fault is actually in uh in series in a conductor so this could be like one screw here and another screw here there's just a loose termination and it's not really touching but it's like really really close and there is enough of a connection to Arc between the two points that's a serious fault so it's arc fault breakers again they have a little board inside of them with a whole bunch of parameters and it says the signatures of a series Arc should look like this and behave like this so when you sense this kind of an activity trip the breaker it's logic that's controlling it the breaker part works so if there's still a problem in the circuit and there's still a short circuit or a thermal trip or a magnetic trip it's still going to trip but it also has the added benefit of the knowledge to know what the characteristics of a series Arc look like and so if an arc were to occur in between these two points it would open that breaker now that's a series a parallel arc fault is same thing it's just between two parallel conductors so it's not in series where you might have a conductor and a device that goes to a load and goes and completes its circuit this is between two parallel points in a circuit so this can be before the load but if there's any kind of arcing that happens between like a hot and a neutral that's what the breaker does as well so that breaker can detect series arcs and parallel arcs that's why we have combination arc fault devices combination doesn't mean ground faults and and Arc faults it means both types of Arc faults both series and parallel arcs so it will do the same thing it'll figure out what what a parallel Arc signature looks like or feels like or is experienced in this electronic circuit and it'll open the circuit [Music] a test environment I know what I'm doing don't do this at home all right so what we've got here is a 220 circuit we got a neutral and a ground so in a normal situation we're gonna have a load and we're gonna have wires that go to a load so how circuits work is by energizing a load can see right here when we have a resistance in the way where an impedance the load turns on no problems no short circuits but if we take the load out of the equation and we touch these together [Music] that's a short circuit we just gave it a shortcut so that's 120 volt short now we can also have a short that is a 220 short so we have twice as much pressure behind this short as we would with the 120. [Music] twice as much smoke too now you'll notice those were with these circuit conductors that had nothing to do with the ground so when we have a conductor that touches metal that's specifically a ground fault yes it is still a shortcut in the circuit but we need to call it a ground fault and this is what that looks like notice now this ground conductor I could touch the ground conductor or I can touch the Box only because this incoming ground is screwed in and is touching the box so this box is bonded so that is a ground fault and it's actually welded on now the next thing we're going to do is an arc fault so I don't actually have any equipment to show an arc fault but Eaton was gracious enough to allow us to use some footage from their YouTube channel where they have arc fault testing so in an arc fault you have an arcing occurring so in this example they have an arc they have two different things that they set a certain distance away they turn the voltage up enough to create an arc that goes across the air gap and you can see the arc causes a breaker to trip so you can see now because there are different things that are happening we need to know that as electricians we need to know if there's a 240 short we need to know if it's 120 volt short we need to know if it's a ground fault because it specifically deals with something wrong with a piece of metal somewhere and we need to know if there's an arc fault because that actually means arcing conditions which can create fire so it helps us identify in the circuit where the problem is so if you're on the phone with your boss and they're like hey what's going on you're just like oh this is a short well dude expand on that like use your brain use your your Lexicon of verbiage to like actually understand what happening because now I can help you diagnose it if you know the right language so I hope that helped you attain some more verbiage and an understanding of why it's important for these different things that we talk about uh love you crazy people thanks for watching and I'll see in the next one foreign [Music]

Channel: Electrician U

Views: 38,263

Keywords: electrician, electrical, electricity, dustin stelzer, electrician vlog, construction, commercial, residential, electrical courses, electrician courses, electrical class, electrician class, electrical safety, electrical code, electrical theory, electrical troubleshooting, home improvement, DIY, how to, wiring, light fixtures, tools, hardware, supplies, trades, homeowners, national electrical code, journeyman, polyphase system, magnetism, troubleshooting, home decor, circuit breaker, trade jobs

Id: 4p-DnlG4YPw

Length: 16min 40sec (1000 seconds)

Published: Mon Jul 31 2023