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Zoom lot. Comm for more information, and now the man who tries to explain makeup air and ventilation to his kids whenever they eat out Brian or so how goes it? I am Brian. This is the HVAC school podcast, the podcast that helps you remember some things that you might have forgotten along the way and maybe reminds you of some things that you forgot to know in the first place about heating ventilating air conditioning refrigeration. That is what HVAC R stands for.

Anyway. A lot of people have commented that the website HVAC our school comm is confusing because it should be just HVAC school, I understand, but that domain was already taken and I like refrigeration, so I included it in HVAC. Our school comm in today's episode is not about refrigeration, it's actually about electrical, and I did a class recently. A lot of you have been emailing me and messaging me saying that you want me to go back to how I started the podcast, where I did more recordings of classes that I gave and that's so that's what this is.

This is a recording of a class that I gave the challenge with recording a class. Is that I'm talking to the people in the class and I'm not really talking to the podcast audience, it's really hard for me to do both and so you'll notice. Sometimes I'm referring to things that I'm drawing and you've got to kind of use your imagination to imagine what I'm drawing, which is challenging for a podcast. Just largely why I want to wait from this format, but you asked for it and you're gon na get it.

So today's podcast is all about electrical circuits and we talked about just the way that electrical circuits are kind of build up. I don't really talk about you know, reading diagrams or symbols of wiring diagrams. I don't talk a lot about that, because that would be really difficult too soon about guess. I probably do a video about that at some point, but you mostly just how circuits are put together and what's necessary for an electrical circuit and line sideload sides, which is all that sort of thing.

So it's a good podcast for a beginner to just start to immerse themselves in the language of circuits, because I think for beginners people who haven't done it. Maybe people who are 2 years or under in the trade and they just haven't done a lot of electrical diagnosis. It's really overwhelming and it's always tricky because ask me about low-voltage diagnosis and electrical diagnosis. More than anything else.

You know they want to learn it, and it's certainly good to do some building up boards and making relay connections and all that. But if you don't do it a lot? If you don't have a lot of experience with actually doing it, it's a hard thing to get your head around, and so I try to teach it in a way that starts to break down the different pieces. So that, then, you can assemble the pieces in the right order in order to get a real circuit that works. So that's what we hopefully do here today on the HVAC school podcast.

So here we go a class that I did the week of November 1st 2017 on electrical circuits today, we're gon na talk about circuits, and this is sort of the culmination of the theory. This is where it starts to be applied, and when people have challenges with diagnosis of electrical problems, it's almost universally because they don't understand circuits. They don't understand how circuits work at some point. There's a misunderstanding there that results in misdiagnosis or trouble with diagnosis.

So we talked about some of the components of a circuit. Yesterday we talked about conductors loads switches and power source. We're not gon na go into super complicated relays or anything. Today.

Next week we're gon na actually assemble some circuits using relays and contactors and light bulbs and switches and all those sorts of things, but today I'm just gon na kind of go over it. So that way, we just make sure we're all on the same page about how it works, because what we usually find out when I go from teaching it up here to then doing it on the board is that everybody nods their heads and says yes. Yes, yes, but then, when we start doing it, we find out that there's very little awareness of how it actually works. So you're gon na want to pay attention to this and ask questions.

If you don't fully understand what I'm saying. Don't worry about asking a stupid question because there are no such things as stupid questions just stupid. People who happen, ask questions, so you nodded your head there. That was a joke yeah.

It just wasn't funny: okay, that's an old chris burrman joke all right! Here we go, we got a circuit, so we start with a power source and we'll call this a 24 volt AC, 24 v AC power source and we write plus and minus. But really there is no such thing as plus and minus. So it's + / / + an alternating current. It's constantly changing right, so we got our power source we have our conductors and now we have some switches or a switch, and then we have a load and that's the load I use is just light bulb to start with.

Let's talk about the different parts of the circuit here because, as far as we're concerned, we see the different components but there's still different parts to the conductors themselves, and this is where, in an alternating current circuit, a lot of guys get thrown off. If they'd like to think of things in terms of direction, they like to think what's coming from this side, and it's going to that side right, it's coming from the left and going to the right is generally how we think about it on a schematic, and so We would like to call the left side, hot or red, I'd like to call the left side common or ground right. That's how we like to think of it, because it's a neat way of thinking of it. But the truth is that isn't necessarily how it really works with the transformer, because, like we mentioned yesterday in the class, a lot of Transformers aren't grounded.

Now, if you take this side of the transformer over here and you ground it, you dedicate it to ground. You connect it to ground. Well now it becomes electrically the same as ground, but you're designating that it's not like that transformer beforehand knows which side is ground in which side is hot because it doesn't. It just has 24 volts of differential potential between those two leads.

Coming out of the transformer on the secondary, we could just as easily ground this side if we wanted, and now this would become electrically opposite of ground now, if we grab both and we have a direct short circuit and the fuse blows if we ground both sides, This symbol means ground by the way I use proper symbols. So that way you get used to seeing the proper symbols when you're looking at a diagram. But do you know why, if I ground both of these sides of the secondary of the transformer, why the fuse will blow okay, so Jake says we're putting the electricity right back into ground and Malky says: there's a short mal, Kees correct. There is a short I'm going to dig into what that means.

I want to address what Jake said, because that's the common misconception. The common misconception is that you're putting electricity into the ground and electricity does not want to go to ground. It has no interest in ground, they don't even like each other. They haven't been seeing each other for years.

Electrons do not want to go to ground where do they want to? Go? Is to the other side of that transformer now, by connecting both sides of the transformer to ground, it's going to use ground to get back to the other side of the transformer when we say ground in that case we're not saying ground like the earth. This is the problem we use ground to mean a lot of different things, but really what we're talking about is equipment ground by that we mean the metal body of that piece of equipment. So if you take one side of this transformer and you connect it to the metal body of the equipment - and you take the other side of the transformer, you connect it to the metal body of the equipment. What are those electrons gon na? Do they're gon na race, through the metal body of the equipment and with very little resistance and they're going to short out and a short, is nothing more than an undesigned path.

It's a path that you don't want the them to take and they're gon na. Take it they're also going to take it at relatively high current, because the resistance is low when the resistance of a path is low. There's going to be high current. So that's why, if you were to ground both sides of the secondary of the transformer it's similar to taking the two leads of the transformer, the cylinder taking the two leads of the transformer, just touching them together, you're gon na blow the fuse, because you're creating a Very low resistance, undesigned path that the electrons can move at great current high current, because there's low resistance and it's gon na blow the fuse trip.

The breaker burn up the transformer or whatever case may be. The weakest point is going to fail. The point of lowest ampacity amp capacity, so the question is what's most likely to blow a fuse or a breaker is a designed, weakest link. So we put that in there as a designed, weakest link.

Now that doesn't mean it's always gon na work. That way, you can have a transformer fail, but you'll see a lot of manufacturers who this is older, but you'll see some residential manufacturers who didn't have fuses in their equipment from the factory or there'll, be cases where somebody say installs a zone zone damper panel or Something and they fail to install a fuse and the secondary transformer, and in that case, when there's no fuse, then whatever the weakest link in that circuit is that's. What will fail if there's a short and often that's the windings of the transformer itself in the secondary? Very thin wire basically and that's the term ampacity. That means amp capacity, how many amps, how much current can this conductor refuse or whatever? How much can it handle before it breaks apart? So it's interesting because the term fuse, so I'm going to confess something as a kid.

This is partially why I'm such a nerd? My parents had this history series. They were cartoons. Okay, this cartoon history series called nest and they had this episode of Thomas Edison and Thomas Edison was struggling with coming up with a light bulb it's when he has this partner, and this is something people don't know about Thomas Edison is he had all kinds of Hell like Thomas Edison was really an experimenter, but he wasn't a super-smart. I mean he was a smart guy.

I don't get me wrong, but he wasn't a mathematician. He wasn't a scientist, he just experimented, but he had mathematicians and scientists with him, and so this guy rushes in and says Platinum we should use platinum, platinum is an infusible, metal and infusible means it doesn't fuse, it doesn't melt, it doesn't break right and so at The time they believed that platinum was an infusible metal, so that point is: is that fuse? In one sense it means to break so when you have a fuse. That means that it's designed to break it's fusible so anyway, a little side. Note there so weakest link is what fails and we create a fuse point, a point for it.

That's designed to break so you don't create damage to important components. The main thing is: is that understanding that connecting this side to this side is a no-no. That's a short okay and if you connect to ground, if it shorts out to ground just shorting, the ground rarely will cause, because some people will say well, okay, what happens when you have a thermostat wire and a chase and it rubs out to the copper? Well, that's gon na cause a short right yeah it can, because what happens is a lot of transformers are grounded, so they do have this one side. This common side is grounded, and so somewhere along the line, and so now, when any of the wires on this side of the equation, connect to copper.

That copper is connected to the metal parts in the condenser, which is grounded, is meaning bonded back and everything is all connected. All the metal parts in your house that contain electrical components and them should be grounded, should have some grounding so anytime, something touches anything metal. It's able to get back to that transformer to the other side and create a short. So you have all these interconnected things.

But ultimately, if you have these two sides touching each other that results in a short-circuit all right - and this is where technicians go wrong. Most often when I'm asking them to wire things, they always want to wire things on the hot side, without reference to the other side of the circuit, because new technicians they're used to wiring up things based on color, they think all right red. So you hook red to the red wire and the air handler and you took yellow to the yellow wire new green to the gray wire or the brown wire or whatever. I'm not gon na go into all the different color uses, but guys get used to thinking.

In things in terms of connecting a color to another color right, but the reality is, is that wire in the air handler the condenser goes to a component, so the yellow wire and the condenser I'm holding up a contactor here. The yellow wire goes to the contactor right. That's what the yellow wire does it's there to make connections easily so that at the end, once it goes through any boards and pressure switches or whatever else it ends up landing here, and this is what guys do when I ask them to start wearing these things. They go and they connect this wire here and then they're lost, so first off they're usually lost with just the colors like well, I'm just used to hooking yellow to yellow.

I don't know where that we yellow where it goes. Well, I'm telling you, the yellow wire, goes to the contactor pulls the contactor in so they land the one wire here and then they don't know what to do on the other side. Well, the other side always has to go back to the other side of the transformer, and so we call that common. But it's just the other side of the transformer.

So the transformer, in order to make it easy for technicians instead of you having to hook directly back to the transformer they give you this nice little terminal block and the terminal block, has an R wire and it has a C wire. So they keep everything. Nice and organized for you, so one side of the Transformers Mark C and the other side is marked R. But you could take that transformer as long as you swap the grounding as well, and you could swap those two wires and it wouldn't make any difference at the transformer.

It's just they're keeping it neat for you, so they're staying one side, we're gon na call our from now on and the other side we're gon na call C. From now on. When you talk about the circuits, though, keeping everything neat and organized in your head is important, because you have this wire here - and this is the wire that feeds into the switch that I'm showing in this switch. It could be a light switch.

It could be a pressure switch. This is what a pressure switch looks like looks like it has a little bell on it just so you can kind of imagine while you're looking at that. Why is that? A pressure switch? Well. Just imagine that if you apply pressure on this bellows that it would open the switch that is they open on rise, this is a normally closed open on rise pressure switch.

Now, if I wanted to make it a open on fall, all I would do is go like this. So now, if the pressure falls, it opens if I want to make it a temperature switch I, instead of putting a bellows on it, I draw this little squiggle at the bottom. I don't know what you call that it's like a squared off squiggle. Now that is a normally closed single pole, single, throw open on fall, temperature activated switch.

Those are the two most common switch types that you're gon na see. There are others, there are lots of others, but these are actually the two most common that you'll see in wiring diagrams and all that, and so now you just learned how to read a wiring diagram there. You go. Congratulations so we'll go over all of this and later time, but I'm gon na describe to you what these different parts of the circuit are called the part of the circuit that goes from hot and again, when we're dealing with an alternating current circuit.

There really is no hot in common until we decide which one is hot in common, we just make it up. We just say this is hot. This is common. Now we've decided all right, but the side that we call hot is on the line side of switches and what does line side mean line? Side means that there's nothing in between the switch and the power.

So you have power and then going into the switch. That's the line side of the switch and you'll see that on a contactor. If you look at the bottom of a contactor, most contactors, bottom or side or somewhere, it's gon na, say l1 and l2, this one doesn't have a lid on it, but generally they're, gon na, say l1 l2 and a contactor. And that means that that's the side that the power goes in, there's nothing in between that and incoming power.

Richard said: that's where the high voltage is right. So that's where your high voltage comes in to a contactor, but doesn't matter if it's low voltage high voltage whatever, when you're dealing with switches the side coming into the switch before the load is called the line side of the circuit. It's the line coming into it. It doesn't have to be a line or it could be lying doesn't matter, but it's the line side right now.

The side coming out of the switch in between the switch and the load. The thing that we're controlling the thing we're powering that's called the load side and it's interesting because this is really electrical more than it is HVAC like HVAC books. Don't really teach this as much, but it's really a nice way to keep your mind around what you're. Looking at and where you're putting your meter leads and what your wiring up, because you always have to have these different parts, and so sometimes you can say what did I do wrong here, all right? Well, what's my line side, what's my load side where's, my switch where's, my load, so line side is easy.

It's the line coming in right. So this is all line side here. This little piece in between the switch the load is the load side. Then you have the load, then you have what we would call common or neutral side.

Now common is a tricky business because it can mean a lot of different things. Common is just one of those words in electrical general, the electrical industry that we just mean all sorts of different stuff when we say common, so you got to be careful with the word common, but that is what it's called, so we can't get around it. That's what we call it sometimes common is grounded, so sometimes it's the same electrical potential as ground if common is connected to ground - and I take a meter put it on volts and I read between somewhere on this common circuit and ground. So I put one probe to somewhere on this common circuit after the load and I measure the ground.

What am I going to read on a volt scale if it's connected to ground, we get a menagerie of different answers here. No I'm gon na have zero. If it's connected to ground, it's electrically the same as ground, if it's not connected to ground well, then you could read a lot of different things, but if it's connected to ground it's electrically the same as ground when two things are connected, they are electrically the same. If there's no resistance, we're comparing ground to the common or neutral side of the circuit, so that's after the load.

We have the line side of the circuit, which is feeding the switch. We have the load side of the circuit, which is after the switch in between the switch and the load, and then we have after the load, which is what we call common or neutral. We call it common and low voltage circuits. Often we will call it neutral in 120-volt circuits and then sometimes we'll, even just call it l2.

If it's 240 volt power, we would call it l2, and this is what I'm saying it really depends on what it is. If you have two separate 120 volt circuits now this is a 24 volt circuit. I mean I already designated that right, and so that's why we would call it common, but what I'm teaching you here is is that, after the load - if that has a name and it's either called l2, if it's high voltage power - and you have more than one Phase, so that would be like 242 circuits that are 180 degrees out of phase. Then that would carry current that's its own leg of power, but in a 120 volt circuit we'd call it neutral, which is electrically the same as ground or should be, and then not a low voltage circuit.

We call it common which in most cases is electrically the same as ground, because in most cases they ground it. In most case they take this common and they connect it to ground somewhere to make it electrically the same as ground. But again when we say ground we're not talking about the dirt, we're just talking about all the metal parts in the building. Now all the metal parts in the building should be the same as the dirt, because we have a grounding rod or whatever, but that's for safety, that's not for typical operation.

So the question was about. Why are you checked on the outlet side of a contactor? You want to check the common what we call common on a single-phase motor when you get into three-phase there really is no common start and run, but when you're dealing with single-phase, we have different designations for each terminal point you read uncommon, because common is the common Point between run and start so you're going to read the entire compressor amps, the cumulative amps of both run and start and start writings, and so generally that's the black wire on the top of the contactor. So in general, when you're measuring amperages you're, usually going to measure the black wire, that's most common, I'm you're gon na read significantly lower. If you read the other wires because you're only reading one winding just remember when you utter the word common, always know that there's room for confusion, always because the common terminal - this isn't a total aside.

But it's a common misconception. Huh, the common terminal, the C terminal on the capacitor, the wires that connect to the C terminal actually go to the run winding of the compressor. What we call the common side of the contactor that goes to the C terminal on the compressor are on the opposite side of the circuit from the C terminal on the capacitor, because all common really means is a common point. It generally means a common point.

It's like where things come together, it's generally a way to of thinking of that, and so a comment on a low voltage circuit means that we have all this stuff going on on the line, side, switches and loads. All this stuff over here changes in each circuit. So you have all these different loads. You have all these different switches.

You have all these different line. Side circuits. Well, mostly, you have all these different load side circuits, there's a bunch of different ones, of these all kinds of different switches that control so like on a let's give an example, typical air conditioner, you have different loads. You have in our market, whatever controls your heat strips right, you have whatever controls, you're, reversing valve and a heat pump, which is generally the orange wire that connects to the reversing valve.

You have whatever controls your compressor, contactor, that's, yellow! Generally speaking, you have whatever controls your blower relay. That's green! Usually you have all these different switches within the thermostat and then all these different colors of load wires that control all these different loads, but they all come back together when they hit what we call common. They all come back to this singular point which it goes to the other side of that transformer. We think of it like it's, the blue wire or the C terminal.

But the truth is that the blue wire to the C terminal just go back to the other side of the transformer, and so this is why organizing your brain in this way - because you can have all these different - let's just keep going here, so you got a Switch here that's a some kind of a switch and you got another load here and it comes back and so now it's hitting common right and you get another switch here, and this is just a light switch and it goes here and controls some other type of Load and it goes back to common - and so in this case, you've got line coming in line coming in line coming in. These are all switches, and then this is all load side. So this is load side. This is load side.

Then you have your actual loads. Then you have your common side and again, this is all made up like we just make up which side of the transformer this is, but in reality we bring it all together to this common point. It closes a circuit. It completes the path because remember the electrons want to make it from one side of the set in the case of a low-voltage 24 volt circuit.

It wants to make it from one side of the transformer to the other side of the transformer. Every circuit has to start at one side of the transformer and make it back to the other side of the transformer. This is what technicians usually get wrong when they wear these up. They'll do this when I give them a switch they'll take a switch like a contactor, because the contactors a switch right.

It goes in and out, and so it comes across here and they'll. Take both sides of the contactor and they'll connect it to something like a low to light bulb or whatever. So if I take both sides of this switch and connect it to something, that's not gon na do anything, that's creating a circuit that looks like this line side load side. That's the main thing that I was wanting to show you before.

The switch is called line. Side after the switch is called load side between the switch and the load. That's why it's called load side, because it's between the switch and the load that it controls. I teach you this way for a reason, because if you think of a switch like what you normally see, then you're gon na get all locked up.

When you see something you don't see, which comes back to that original thing on the list which was working on equipment, you haven't seen before there's all kinds of different switches, there's all kinds of different loads. But once you understand the basic principles of switches, loads line, side, load, side common, you understand different types of switches and then you understand sequence of operation for that system, because every system is going to publish its sequence of operation. This happens, and this happens in this happens right once you know those things, then you can always put the pieces together, cause it's like building something out of Legos. Here's.

What you're saying to me right now, when you say where's the contactor in all this, I'm showing you how to put together Legos and I've built you a horse and I've built you a car, and I built you a house and then you say, but where's the Castle, like I don't understand where the castle is here, contactor is just a type of switch, I'm not criticizing at all. This is very common to everyone, but you have to get away from thinking of things as a contact or a relay and instead think of it. As a switch and a load, because that's what it really is, this load controls this switch. That's all it is, there's a switch, that's controlling the load and so there's a thermostat.

That's the switch, that's controlling the load, and so I have a load side coming out of a switch which is a thermostat, that's the yellow wire. So the yellow wire is a load side conductor, a line side conductor is the red wire. Let's draw this, so we got a transformer one sided transformer we're gon na call common. We just decided that it's common and we're gon na go ahead and ground it.

So that way, there's no question. This is coming out of the trench from relying sides over here. We're not going to worry about line side right now, but we're talking about the low-voltage side. This is what we call the common side here right.

So that's we're gon na keep this over here on the right. So we know what's up with it, and now we have what comes out of the other side of the transformer hot. We call it hot it's a red wire in almost every case right, so we got a hot, it's our so now this red circuit everything before it hits the thermostat. That's the line side, because it's before a switch, the thermostat is the switch.

It's also a load, but it's primarily a switch. So we have this thermostat we're gon na draw it and it's got an R terminal on it and it's got a yellow terminal on it and it's got a G terminal on it and it's got a white terminal on it and it's got a C terminal on It and it's got an O terminal on it. Heat pump number said we do two heat pumps here, alright, so now we take this red wire and we connect it to the thermostat. Is this red wire between the transformer and the thermostat? Is it line side or load side, its line side? Why? Because it's got no switch in between there's.

Nothing in between. It's just goes straight to the transformer right. So that's line side. Now we've got all of these load sides because they're coming out of the switch.

The switch is the thermostat, so now we got this yellow wire going to a contactor Y terminal. Now this is load side, because now it's in between the switch and the load and what is the load in this case, the load is the coil of the contactor, not the switch of the contactor, because the switch to the contractor is the high voltage side. We use the load of the contactor, so we're gon na go ahead and draw a contactor here, because you guys, like your contactors around this joint, get a contactor here. We're gon na draw it as a single pole contactor, because we see a lot of those and you got your little side terminals.

These little terminals on the side represent the low-voltage terminals on the coil on the side, so yellow comes out and it connects here. So this is all the yellow wire between the thermostat and the contactor and they connect together in the air handler right. We know that at the air handler there's a center point, but it doesn't matter just taking a path out to the condenser to that contactor. So this is all load side, because it's in between the switch, which is the thermostat and the contactor which coil the contactor coil it's an electromagnet.

It does work, it has resistance. You'll agree with that. Electromagnet coil does work as resistance, so it's a load and then we take the other side and where does the other side of this contactor coil go to? This load goes to the comm and nailed it Malky all right. So it goes to the common boom.

So now this is all what we would call common side, and this is where it gets tricky. It goes by different names, depending on the type of system you're working on, but it all works the same way or I shouldn't say all, but in most cases on the stuff we work on it works the same way. You keep this common or neutral or l2. All on one side by itself, so it's just over here by itself.

All the fancy stuff is done on the left side of the diagram. If you will, in most cases on the hot side the line side going into the switch, then the load side coming out of the switch going to the load, and there could be a bunch of other switches in here and fact. In a lot of cases there are you have safety, so in this load side of this circuit there may be a low pressure switch. So a low pressure switch would look like this high pressure switch will draw one of those that would be normally.

These are all, but it opens on rise. This opens on fall, I'm drawing pretty messy sloppy work here, but you get how that works now, and this is all load side, because it's coming out of the main switch that controls it now we would still say if we were describing this particular switch. We would call this the line side of the switch and we would call this the load side of the switch, and in that case that doesn't mean this is all load side. But we call it the line side of the switch, because it's the line coming in.

It's closer to the incoming power than it is to the load. The part that's on the load side, meaning it's closer to what it's controlling is called load and the side coming into. It's called line - and this is super useful language like if you're talking to electricians, you're talking to anyone, the ability to know the difference, train line and load side is really really useful to you. It's not necessarily what we would call line side it's what we would call the line side of the switch, which means it's closer to the line.

It's the power coming into it versus going out now again. Is there really any power in or out? No, it's alternating. Current, it's not one directional, but because we're organizing everything in our brains, it's for us to keep track of things. We say.

Alright, this is the hot side, so it's closer to the hot side. Therefore, it's line it's closer to the transformer. It's on the transformer side, and if it's closer to the load side, then it's what we call the load side of the switch. So the question was everything that comes down the thermoset is load.

If you ask an electrician, this they're gon na say what are you talking about like that's, not how we talk about this at all, but this is how I train it, and this is a really effective way of thinking about it. Everything coming out of the thermostat is the load side because it's controlled by a switch, so everything coming out of the thermoset is controlled by the thermostat. So we call it the load side of the circuit because it's constant power, it's controlled by a switch. I know I'm gon na get a lot of complaints on this particular way that I teach this.

But it's super useful trust me. The other side of the contactor is now common, it's all common, because this is 24 volts. That's what we call this. I'm gon na keep reiterating this that so we had a guy one time who wired the common side, the blue wire out of the low voltage to the c-terminal on a capacitor.

Do you understand what I just said: they're, the c-terminal and capacitor? Is it high voltage or low voltage high voltage, the C terminal on the low voltage side? I just said it is low voltage, but they both called common. So he's like. Oh, I just hook all the Commons together, he wired the C terminal on a capacitor to the C terminal. The common on the low voltage low voltage is going to power, the low voltage loads and it's the opposite side of the low voltage loads.

Is that low voltage common and he connected that to the C terminal on a capacitor which is totally unrelated and it's high voltage. So it blew the entire low-voltage circuit, and this is when guys, just settle in and start thinking about, colors and only words and not understanding what the colors and words mean. They'll mess things up in common is one of those words where there's lots of things called common. Just because it's called common doesn't mean it's ground doesn't mean it's high voltage or low voltage.

It just means it's a common point where things come together, so you got to know what kind of common you're dealing with run goes to the capacitor side. That says common. The C on a capacitor is the common point between the two capacitors in a dual capacitor: dual capacitor has two capacitors within it, and that C terminal is the common point between the two and that actually goes to the run side. Not the common side of the compressor.

This is one of the most common things that people mess up when it comes to wiring. I did an article on this and experienced guys are like how could you ever make that mistake, but it's understandable why you would make that mistake because of the words the words confuse you, the terminology is confusing. So when you're dealing with the high voltage side of a contactor, I'm going to quick draw that so that way, you understand it because we're getting a lot of questions about that. So you have the line side of the contactor.

We'll draw this one. As a two pole contactor, so this is the line side and this is load side. What does that mean line? One in line two of high voltage power? We're going to take the contactor here? We're gon na go from one side and we're gon na go to common on the compressor. This is the load side, because it's controlled by the switch.

The switch is the contact points. Now the contactor is a switch in the high voltage circuit. It's a load in the low voltage circuit. These here are switch controlled by this low voltage load so contactor.

I just drew it the right side here to comment on the compressor. But let's say we have a dual capacitor here we have a herm terminal. We have AC terminal and we have a fan terminal, here's where it gets confusing with the C's now out of this side. Here we connect one wire from this contactor to run and on this I'm drawing elf you're, not necessarily always going to see this l1 and l2 t1 t2 doesn't really matter which direction you have it.

It's just there for reference, but this is the load side. This is the line side and so now, coming out of this load side, we've got one side goes to run. One side goes to common I've a little outside, and now we've got to feed. This start winding right.

Well, this is where it gets confusing. So now we take this run side and we go to the C terminal on the capacitor and you'll notice. The C terminal on the capacitor is connected to the opposite side of the contactor than the C terminal on the compressor and now Herm goes over to the start terminal on the compressor. That's a high voltage, compressor circuit, and so where are our lines and loads? Well, we've got line side here got our switch here now we've got our load side wires.

This is where it gets a little bit more confusing, so we would call this load side being controlled, but in this case we're breaking both sides, because this is a 240 volt circuit. So you have two legs of power and a 240 volt circuit. So really, there is no common in a 200 volt circuit, there's no neutral, there's, no common, no neutral! Both sides have power. Now we tend to do more of our switching on one side than the other.

Typically, but in this case we've got a two pole contactor. So now, really everything is all load side on this. There really is no common, because it's all being controlled by switches. So when that contactor opens everything is de-energized, because on this l1 and l2, coming in, you have 120 volts on both legs opposite phase.

So when this one is positive, this one is negatives, and that makes your total of 240 well. The fan is connected in essentially the same way. It's the only thing, so you have your common and run are on opposite sides, l1, l2 and then your start winding. On your fan, use your brown wire right, and that goes to the fan terminal on the capacitor and capacitors are confusing.

That's a whole nother thing, because a lot of people would say the power coming out of the capacitor is what's feeding, but it's actually not how it works. It's just towards it right exactly we step down transformers, that's what we work on, but there's step-up transformers too. So the primary is just the side that has power applied, it's the applied side, meaning that's what's going in that, and the secondary is where it's coming out at. You can actually swap them too in a lot of cases, but anyway, you're asking.

How do you test a transformer, so we got a picture of a transformer up here. You check power coming in with your two meter leads on volts you'd say: do I have 240 volt 120 volts, whatever the appliance is? Do I have it going into the transformer? Yes, I do we'll say we have 240 volts going in and it's wired properly and then we go right to the outlet, the two secondary's coming out and you test there do. I have 24 volts or whatever it's designed to step down coming out, always between two points: you're always checking potential between two points and it's always best to not use round, because ground is a finicky mistress. Sometimes you have everyone wan na say you have no choice but sometimes you're using it for a reference point or wherever and that's okay, but in general you want to be reading between the two things you're attempting to really know do.

I have potential between these two points I have potential coming into the transformer. Do I have potential means voltage coming out of the transformer at the designed voltage, the same way that, when you're measuring a contactor, if you want to measure potential coming in 240, volts, okay, 240, volts? Okay, that's where you would measure that? That's how you would measure that a lot of guys do this. They go to ground, so they start going here to ground here to ground here to ground here to ground. Well, that's not a good idea! That's going to create a lot of confusion for you, a step up transformer steps voltage up instead of stepping it down.

So why would you use it? An example would be you'll see it in things like electronic air cleaners that are creating very high voltages. There's all sorts of different applications, but not mostly in our industry. It could go from 240 volts up to 2400 volts. Any voltage that you want.

You can step up or step down any voltage to any other voltage, and now the current carrying capabilities of that secondary are still totally dictated by the primary. So if you're limited in what work you can do in those cases, but generally speaking, we see step-down transformers. We see that all the time we see step-down transformers at the road in every building, we're up in the pole or on the ground. That's a step-down transformer! So next week we're gon na start actually because it's much easier for me to show you how to use the meter and walk through the circuit in a live circuit and we'll talk about some of that.

But then we will also actually wire up some circuit. Just so you're prepared, if you come in on next Tuesday, because we're not doing class again until next Tuesday come in next Tuesday. What are we gon na be doing we're gon na be setting some things up on a board and you're gon na be wiring? Some basic circuits, so if you feel uncomfortable wiring basic circuits, then you're gon na want to study up on that, because this is what guys always do. They start.

They take power and they go in and they bring both lines into a switch. And then they don't know what to do so understand you go power line, side, switch load, side, load, common or other side of the circuit cool, very good. Thank you. Hey thanks for listening to the hvac school podcast.

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