Capacitor and Hard Start Myths Busted

we're going to talk about capacitors [Music] anybody know the symbol for a capacitor first off i'd like to do a little little diagram type stuff while we talk through how things work like a circle with a cross or something a circle with a cross so like this wow that's like that is that it's so those are just the connecting lines so you're going to notice something in this symbol in the words of dave matthews okay it's the space between that we need to focus on here the space between sorry these two sides aren't touching you notice that there's not like a connector between these two halves and so when we draw a capacitor in a circuit let's do like a basic compressor circuit common start run would be typically how you do this and you have your hot coming in this side which goes to run and then you would go to your capacitor and then that would go to start and then common would go to l2 that would be that'd be the typical way what you're going to notice here is that start is fed through this capacitor and on if this was a dual cap this part would be called c and this part would be called herm we connect the herm side to the start terminal on our compressor so we're doing some learning here while i'm drawing the diagram but this part here this l2 or whatever oh i drew l2 both sides wow this l1 on this side here is connected to common on our capacitor in this case if it was a single cap they wouldn't even have a designation you would just have two terminals but there's no connection between this side and the other side so how do the electrons make it through this capacitor to get to the start winding does anybody know anybody there's a little person in there is there yeah he just he just kind of shuffles him he kind of pokes an electron over there like hey no the answer is is that the electrons do not actually make it from this side to this side that's not how that works so it doesn't travel through the capacitor we may imagine that it does so in our imagination we see a capacitor what do we think is happening in there this is just imagination time there's no judgment here because i think we've all imagined different things what do you imagine is going on inside that capacitor the pass there's a battery and it's running the compressor the capacitor is a battery and it's running the compressor what else the dual run the commons applying power to both the fan and the herbicide okay the dual runs applying power to both the fan and the herm side but like it makes the connection basically in my head okay it makes the connection okay what else the power comes in and it gets larger and then sends it out the power comes in it boosts it up and then it sends it out to the compressor to the motor on the herm side right what's actually happening because we imagine that somehow the capacitor is like boosting does this sound right okay that's somehow boosting the voltage or the current or something it's boosting something that's good right does that sound right yeah it's like something with electricity is getting boosted inside that capacitor well here's the thing it's actually the opposite so a capacitor is actually restricting current it's reducing the amount of current but it's also creating a phase shift and it's that phase shift when people say that that's like magic talk what does that mean we're not even going to focus on that too much but the idea that a lot of people have is is that the bigger the capacitor the greater the phase shift and that's not true the bigger the capacitor and microfarads micro farads the little baby ferrets i love ferrets so much they're so cute i just love ferrets and these are little tiny ones the amount of microfarads dictates the amount of current that can travel into the start winding or through the start winding i should say but our imagination that it's going this way going through the capacitor and getting boosted up is actually incorrect the capacitor is like a balloon or like a does anybody know how a pressure tank works for like a well pump where it actually has a membrane inside the pressure tank and so as you pressurize it it kind of it kind of fills up and then it maintains the pressure so that way your pump doesn't have to keep cycling on and off all the time kind of has a balloon in it almost you can kind of imagine a capacitor like that or imagine that it has it that it has a membrane here and it pressurizes and stores pressure and then releases it so it's like a balloon storing pressure and then releasing pressure so as that sine wave as the voltage changes because in alternating current we have this constant changing voltage right everybody buy that if i measure with an oscilloscope or something that's going to actually show the voltage changing on that outlet on the wall it's not going to always be 120 volts it's going to be going anywhere from about 150 volts down to zero and it's just going to keep doing that over and over and over again right so when we measure a voltage we're just kind of measuring an average it's something we call r we call rms root mean square which is basically a mathematical way of saying what is the average of all these voltages that keep changing does anybody know how often the voltage changes how often it runs through a full cycle 60 times per second that's when we say 60 hertz that's what that is frequency how frequently does it go through an entire cycle of up voltage down voltage up voltage down voltage that makes sense so in the us we use 60 hertz that's 60 cycles that's a frequency of 60 hertz a hertz is the term you use for that in europe and a lot of other places they use 50. it's how fast the generator is actually spinning at the at the power plant that's literally how fast that's spinning and or how fast it's transferring between poles on the generator more specifically all that means is is that this little capacitor this little balloon is inflating and deflating 60 times per second can you imagine that i'm going to wait until that kind of locks into your brain it's inflating and deflating 60 times per second and in a balloon when you're pushing energy into the balloon the balloon kind of expands but then it goes back out the same way it came air goes back back out the same way it came in and that's the same thing that happens in a capacitor so it pushes in oh i'm losing my marker oh no oh my gosh it pushes into the capacitor and then it pushes back out the same way that it came so when this connects to herm the start terminal on the on the compressor it's actually going in and out of the start terminal on the same way that it came in now the reason that it stores electricity in the capacitor this is kind of like strange magic but it's actually an attractive force between the two plates because we just have so much surface area so there's a potential difference difference in voltage across the capacitor and we have all these metal plates that are wrapped around in a big ball inside the or like like a roll a giant roll inside the capacitor they're all rolled up it's just a sheet of plastic with metal applied to both sides and so that surface area even though they can't touch creates an attractive force the electrons store and discharge store and discharge so in that sense it is like a battery so when we say it's like a battery it's like a battery in the sense that it stores energy but it's not like a battery in the sense that with a battery we store energy and then we release it slowly over time in a capacitor we're storing it and releasing it 60 times per second completely completely storing completely releasing 60 times per second we're doing that yes because it creates a phase shift which helps create kind of that third hand to spin a motor if you imagine the best way i can i've always thought of it you guys know what a pinwheel is pinwheel like you blow it like it's got the little pin in the center and you blow it and it spins a little debbie cake are you always thinking about a little debbie cake i just could also be like a little cookie okay all right is everybody thinking about cookies right now why is everybody focusing on cookies no but if you imagine something that you're trying to spin okay so imagine we've got a wheel it's like a wheel of fortune wheel right what do you do if you want to spin the wheel of fortune wheel what do you do do you go do you just push on the side like it's not spinning right no what do we do we go spin right the force of our hand is applied directionally it's not applied laterally on the sides and if you imagine 120 volts and 240 as this sort of like side force where they're just directly opposing one another what the capacitor is kind of doing is it's giving us a third little hand that helps us get it going in one direction and now we apply force on the sides and that kind of keeps it spinning but in the case of our typical psc motors that we have our typical condenser fan motors blower motors compressors that we work on day in and day out single phase this start winding is actually kind of misnamed because we imagine because it's called the start winding that means that it's only in place when the system is starting but it's actually not it's in place all the time the start winding is always having curtain run through it now again this is where when i put out these videos the three-phase guys are like this has nothing to do with us and that's true in three-phase you've got three hands that are spinning and you don't need capacitors that's why you don't see capacitors on three-phase motors in single phase that's where we use capacitors specifically singer for single-phase psc or cscr in the case of ecm like sam talked about a couple weeks ago we also don't have capacitors i mean we do but not in the same way why don't we see capacitors if you have a ecm blower motor because you've all noticed this right do you have a capacitor on an older blower motor and on newer x13 as we often call them or ecm blower motors we don't have a capacitor do you know why that is it's kind of built into it it's kind of built into it yeah but what's built into it the modules built into it what does the module do what is that what happens inside that module it's like a balloon and you're just trying to copy my words wrong false there is a little energizer's different magnets one time no and that one i think there's a little man on a hamster wheel man on a hamster wheel yeah he does that feller that feller and his hamster wheel well no wonder they failed no so an ecm motor is really a three-phase motor i'm gonna make this really simple in the same way that you go to a commercial job and that three-phase blower motor that three-phase condenser fan motor that three-phase compressor doesn't have a capacitor that's the same reason why you don't have a capacitor and an ecm because that ecm is really a form of three-phase motor because what's happening inside that module really simply is it's taking power from the utility 120 volts 240 volts whatever and it's changing it into three phase and it's not just changing it in the three phase it's changing it into three phase that the frequency can be modulated based on electronic controls so it's not just 60 hertz anymore on an ecm it could be 40 hertz it could be 80 hertz it could be 20 hertz the frequency has changed but it also turns it into three phase so now you've got three little hands again imagine again and this is just the easiest way for me to think of it if you're trying to spin a spin a wheel a fortune wheel and you've only got two hands and all you can do is slap on the sides it's going to be really difficult to get that thing spinning and that's what 120 volts and 240 volts does when you've got three hands positioned like this and you can do this now you can much more effectively spin a motor and utility actually always starts out with three-phase from the power company there's three phases but we use a single phase in residential so we take one of those phases off and we use that to power the entire house and when we make 240 we take that single phase and we split it into two phases by center tapping a transformer but either way whether we're using one in the case of 120 or we're using two in the case of 240 we don't have three hands to work with and so the capacitor back to the back to the basics here our run cap gives us that third hand that helps spin that compressor but here's the thing if we have too small of a run capacitor in the system what does that do to the compressor let's say that it's designed for a 30 and we put in a 10. what happens to the compressor it doesn't start might not start might not start it's not going to start smoothly at best right so what's going to occur inside that motor if you have a capacitor that's too small you got a baby shot in the wheel portion we got a little baby hand trying to spend the whole fortune right so it's going to get hotter right but that heat is not going to be where we imagine because we imagine if our if our run capacitor is too small that it generates heat in our start winding that's what we imagine but that's actually not true it generates heat in our run winding so if you've got a compressor i'm just going to make this really simple if you've got a compressor that's having a hard time starting so what does it do you walk up to a compressor it's not starting what's that what's that what's that thing doing right but what's actually happening inside that motor what's happening baby hands it's getting hot baby hands are slapping it but she ain't spinning right i'd say i like this benny's got good metaphors here he's working with my metaphors sam just rolled aside yes so that thing's getting hot but the heat is occurring in the run winding if you check and you check start anybody ever check start amps or lock rotor amps on a compressor put an amp clamp on common and see what those amp and what those amps are when it's not starting or when it first starts what are they they're high they're high right they're high when they get started it takes a lot more energy to get that started from nothing to moving up to speed right and what happens when the when it stays locked they stay high until the thing goes out on thermal overload if we have a capacitor that's undersized what's actually happening it's not allowing enough current to move into the start winding it's not allowing enough to move through the start winding i should say because our balloon is too small if our balloon is too small then not as much current can move through the start winding because that balloon fills up faster and this is literally what's happening in terms of charges not in not as many electrons can store in that capacitor when it's a smaller capacitor that's exactly the same thing that happens when a capacitor is weak so i have a lot of people say capacitors never go weak they're either failed or they're good or bad right is that true that's bunkum i don't know why people say that and maybe it was 20 years ago back when people used to use the word bunkum capacitors do get weak and when a capacitor gets weak what does that result in it results in that that motor not starting as quickly as it should which results in stress on our runwinding because our runwinding is staying hotter longer than it should does that result in stress on our start winding the answer is no because if the start winding has a capacitor that's too low then the amount of current moving through it is low and when you have low current you also have low heat what happens in our start winding if our run capacitor is failed completely what happens in our start winding nothing right because without this balloon filling up and discharging 60 times per second no current whatsoever moves through our start winding does our start winding fail when we have a bad capacitor the answer is no what does fail when we have a bad capacitor are run winding why because it's sitting there getting powered across the line and that then that motor is locked and it's just heating up until thermal overload takes it out thank god for thermal overload otherwise that uh that uh run winding would melt the first time the compressor locked it would just until it just until it just became the thermal overload by melting the winding when we go to a system that has a failed start winding often that failed start winding is due to somebody either putting in too big of a capacitor wiring the capacitor wrong i.e across the line so that way the start winding is getting the full current of the system or some sort of start gear like a hard start kit start relay start capacitor something that they were either wrong or put in something too big or incorrect potential relay size or something like that so when you go to a system and it's not starting what are some things you should do first let's go through some practical things compressor you go up drawing high amps what do you do next visual inspection visual inspection is first right and what are you visually inspecting wires connections wires connections that is properly wired inspect not just that the capacitor is is uh rated properly but that is the correct size for the for the motor that it's connected to is it possible that somebody could have changed a capacitor with the wrong size no never that would never happen right of course it is is it possible that they wired it wrong of course it is is it possible that they put some weird accessory in there and wired that wrong of course it is is it possible that the wire terminal connected to the contactor is on the wrong spade yes is it possible that it's melted on the contactor yes is it possible that it's loose on the capacitor yes is it possible that it's disconnected from the compressor because it's melted yes is it possible this disconnected from the compressor because the last guy who checked it didn't connect it on properly and then it fell off yes you get the point so visual inspection is where it starts all of those things i just mentioned after you do that and it's still not starting then i would also check check the capacitor obviously check the rating make sure it's the right one see what it's see what that's doing but then even after all that let's say it's an older system compressor's still not starting what's the next thing you would do check see if it's a thermal overload well if it's in thermal overlap it isn't thermal overload because when it tries to start it shuts off and goes into thermal overload but if you heard it going you know it's not and i mean you know it is in thermal overload because it is locked and overheated but if it's trying to start thermal overload's not the problem thermal overload is a result of it trying to start and being locked what do we do next eight year old compressor 10 year old compressor 12 year old compressor we've done all of this we've checked the capacitor we've visually inspected everything and it still won't start what do we do that's right but try a hard start kit right and is that a bad thing to do absolutely not that is the right thing to do but what does a hard start kit do a lot of people will say it adds an additional phase shift wrong it does not add an additional phase shift the phase shift is already occurring in your run capacitor what it does is it gives you a bigger balloon so it gives you more current to hit that start right winding with but here's the trick that start winding ain't designed for full current all the time so now when you put this big old capacitor in there to give it almost unlimited current what do you have to do with that bigger balloon that you just hooked up turn it off you have to turn it off bert's answering all the questions now you have to turn it off right because if that larger amount of current keeps moving through the start winding all the time the start winding is going to fail because it's not designed for that it's not designed for constant duty with higher current is it designed for constant duty yes obviously because the run capacitor is connected but it's designed for constant duty at a lower current go ahead bending the same thing as like oversizing the capacitor it is but the difference with oversizing a capacitor is is that there's nothing to take it out of the circuit once it gets started so a start kit gets it started and then brings it out and that's what a potential relay or a current relay does it's there so that way once that motor gets up to near full speed it takes that start start cap out of the circuit and now allows it just to run on the run capacitor alone what is the right hard start kit the best hard start kit to put on a system the one that the factory specifies for it and there almost always is going to be a specified accessory hard start kit sometimes you don't have one using an aftermarket especially on an older system that you're just trying to get a couple years out of it that's fine and that's why i have no issue using hard start kits for that case or even in cases where we have some customers in 208 voltage with really long electrical circuits that have high voltage drop as long as we've established that it's working well i'm okay with it in some cases especially in cases where the factory doesn't really specify an accessory hard start kit but generally speaking hard circuits are we should install factory ones and only as needed only when the the situation requires and in some cases like long line sets um the factory will specify it and say that this should have a factory hard start kit in it but just keep in mind what that's doing is it's just pushing more current or allowing more current to move through the start winding for a very short period of time it's not some magical voltage boosting device it's not a magical current boosting device it's just given a bigger balloon so that way more can move through in and out well all that i'm trying to do in this class you know introduce you to some symbols and a few things but just change your kind of the cartoon in your head of what's going on inside the system because things will make more sense then if you run into a failed start winding and it's like yeah this does have a hard start kit on it right there don't replace that compressor without replacing that hard start kit and don't do it anyway like if you go to a system with a failed compressor on single phase and there's start gear on it like a hard start kit that start gear needs to be replaced with factory start gear when we replace that compressor because because it is the most likely cause of electrical failure if a potential relay locks closed that'll result in that start winding always taking that higher current so that big balloon staying in all the time and that will cause that start winding to fail what do you replace when you replace the compressor factory start gear which should be hard start kit capacitor all that make sure because in many cases you may get a new replacement compressor that's a superseded compressor that might not actually take the same capacitor as the one that was in there that happens so you need to make sure the capacitor is the right size so let's end with this what happens in your start winding if your capacitor is too small it's not getting enough power it's not getting enough current right so it's going to be less likely to start if it doesn't start or it takes longer to start then the run winding takes a hit it gets hotter than it should okay what happens if you put in too large of a run capacitor it'll apply too much to the start over time it'll weaken the winding exactly over time it will cause because you're applying too much current to start over time that start winding is more likely to fail so there's more heat concentrated in the start winding than it's designed for so is it okay i just go a little bigger is that okay no i just go a little smaller is that okay no why because of the reasons we just mentioned now if you've got a 50 and you're going to go up to a 55 you know that the capacitors actually a lot of cases out of the box are a little weak and then weaken over time anyway so would that be acceptable you know use your judgment in those cases because as a percentage that's not a significant increase and but this is where a lot of people say well yeah the thing's rated for you know five but i'm going to put in a 7.5 because that's all i've got well as a percentage that's a huge percentage increase the percentage difference between a 50 and a 55 is a very small percentage increase don't use a 7.5 to replace a 5 don't use a 10 to replace a 7.5 but either way is not good for the compressor too weak is not good for the runwinding too too large is not good for the start winding make sense and hard start kits use them when we gotta unlock a compressor especially on an older system where we're just trying to keep it running for a while for the customers benefit and use it where the manufacturer specifies it if the manufacturer specifies it use it but use the manufacturer's specified one may take a couple days to get in but they all are if they're going to specify it then they're going to have a specific kit that they specify with the right potential relay and the right start kit to act or the right start capacitor to accomplish the task of getting it started but not overheating it so if it's not getting its voltage from l1 because it's not actually connected where does it get its voltage from oh you mean the start winding it's actually coming through l2 so it's going pressurizing the balloon and then it goes back the other way pressurizes the balloon goes back the other way it's connected to the other side because that's what allows the attracting force the attracting electromagnetic force that causes the electrons to store and then discharge if i were to just disconnect this now there would be no attracting force and now the balloon doesn't work so that potential difference is what drives the capacitor but a capacitor is a super simple thing it's a run cap is a it's a metal cylinder inside is a jelly roll of plastic sheeting with metal coatings on both sides that are connected to the terminals and a bunch of oil filled in the inside in order to keep it from overheating that's all crazy simple so if it's dispelling the energy 60 times a second for 60 yards what causes the faster to store the energy if you were to disconnect power sometimes they store the energy uh if you if you it just depends on where it was in the cycle when it was disconnected so there's no there's no like you can and this is actually a fun thing to do it's not really fun but it's fun for me is that if you take a capacitor for example and you hook it up to an outlet you can literally take one side hook it to one side of the outlet the other side hook it to the other side of the outlet right and then disconnect it check the voltage on the capacitor it might be 50 volts do it again disconnect it it might be 30 volts do it again disconnect it it might be 90 volts it just depends on the moment that you disconnect it where was that sine wave in the cycle the capacitor does not a lot of people will say this is another goofy thing they'll be like oh man if you disconnect the capacitor you throw that up and that thing stores thousands of volts it's like no it stores whatever voltage it was connected to when you disconnected it whatever it happened to be it doesn't somehow boost up the voltage some crazy way people get confused because a lot of times capacitors are involved in like inverter driven systems that have higher voltages intrinsic to that design but that's not the same thing as a typical oil fill run capacitor that we use or a electrolytic start capacitor those are literally just slaves to whatever the incoming voltage is that's all they do they store they discharge that's it their whole lives nothing else fancy going on there you know for the sake of the video whenever i do these things i get tons of pushback that's not how that works at all it creates a phase shift and it's a magical world of make-believe and it's like just cut the things open see what's in them they're like the world's most simple devices um don't obviously complicated cover up complicated electrical id or incomplicated electrical ideas for things that are very simple for what we do it's helpful to understand this because when you see a failed runwinding now you know where to look when you see a field start winding now you know where to look it's helpful when you're discussing with the customer so you don't tell them something crazy that then makes you look dumb later on if they ask for their questions or heaven forbid if they're an electrical engineer those people are always fun all right thank you all have a great week thanks for watching our video if you enjoyed it and got something out of it if you wouldn't mind hitting the thumbs up button to like the video subscribe to the channel and click the notifications bell to be notified when new videos come out hvac school is far more than a youtube channel you can find out more by going to hvacrschool.com which is our website and hub for all of our content including tech tips videos podcasts and so much more you can also subscribe to the podcast on any podcast app of your choosing you can also join our facebook group if you want to weigh in on the conversation yourself thanks again for watching [Music]

Channel: HVAC School

Views: 213,072

Keywords: hvac, hvac school, Capacitor, Hard Start, Myths Busted, Kalos, techs, capacitors, diagrams, service calls, hard start kit, boost, voltage, current, microfarad rating, start winding, alternating current, root mean square, motor, directional, horizontal, force, ECM, single-phase, equipment, run capacitor, undersized, run, rotor, amp draw, circuit, OEM, sizing, air conditioner, hvac technician, hvac training videos, Bryan Orr, hard start kit wiring, hvac basics, hvac system, Hvac troubleshooting

Id: 5i5jmGBGKxI

Length: 28min 41sec (1721 seconds)

Published: Fri Mar 11 2022