All right so we're gon na get started. I don't know if you've ever seen this. This is one of my favorite places to start electrical diagnosis. It's it's probably hard to read this on your screen, but there's a quote in here.

This is page 48 and this is an old-school electrical diagnostic guide. It's I forget the title of it, but this is from the I believe this version is from the 1930s, but I'll read it to you. It says electricians often test circuits for the presence of voltage by touching the conductors with the fingers. This method is safe, where the voltage does not exceed 250 and is often very convenient for locating a blown out fuse or ascertaining whether or not a circuit is alive.

This is my favorite line. Some men can endure the electric shock that results without discomfort, whereas others cannot it's they're. Definitely man shaming you if you can't, if you can't grab 250 volts and use it for electrical diagnosis. 1930S man is looking down on you right now and then it goes on.

If you go to the next page and stuff that actually talks about checking low voltages by placing the wires in your mouth - and I think it says it says - the president see this yeah there - it is actually whew. Looking at the bottom, it says the presence of Allah voltages can be determined by tasting. This method is feasible only when the pressure is but a few volts, and hence is used only in Bell and signal work where the voltage is very low. The Baird ends of the conductor's, constituting the two sides of circuit, are held a short distance apart on the tongue.

If voltage is present, a peculiar mildly burning sensation results anyway. They literally used to teach this and and there's no huge technical benefit to this other than just to point out that long ago, people were much maybe much dumber, but also much less risk-averse than we are today and I'm not gon na pass judgment either way. But just to say that this is how things literally were taught not in the field, no, no actually from the book. So there you have it.

It's actually a great book, though, so we don't recommend that you that you do this anymore, probably probably not the best. Probably not the best practice all right. So let's talk about the cartoon in our heads because I think from in terms of electrical diagnosis. This is something I guess I probably wasn't born with it, but a lot of people who are really good at diagnosing electrical circuits.

Electrical problems of a mindset of like imagining things in there in their mind, they may not actually represent reality perfectly, but give us a give a good enough picture that they can sort of. I don't know, I don't know how to explain my brother and I just call it the cartoon in our heads and so this image here, volts, amps and ohms is one of the most common. That's that's taught, and it's a good one. I mean this is a kind of a modern version of this.

You know you volts, volts are the pressure, ohms are the resistance and then amperage is the actual current that flows, and so when you increase resistance, you decrease current such an interesting thing, because one of my favorite questions to ask people is that what happens to your Amperage, when resistance goes up and they'll often answer that your amperage goes up and the thinking in terms of electric motors, so you say you know if your resistance goes up and the motor windings does the amperage go up or down and they'll often say up well Of course that's wrong when your when your resistance, when the ohms increase, then mister amp here, doesn't get pushed through the circuit as easily. But why do people think that they think it? Because when you think of an electric motor when there's greater resistance to the shaft moving, so if you have greater force against a blower wheel, if a compressor, you know having a hard time running because maybe it's got bearing wear or it's running against. You know running high compression ratio, something like that. Then we run higher amperage and so we think resistance equals higher amperage.

But that's not actually true in the windings when a motor gets bound up. So when it can't turn the resistance and the windings actually is less and that's because of something called inductive reactance as a motor runs up to near synchronous speed, you know the actual frequency of the electricity, that's entering the motor as it gets closer to that synchronous. Speed, there's actually a type of resistance, that's generated as part of back EMF and that's called inductive reactance and that inductive reactance acts as a type of resistance against the current. And so it's just.

It is the same thing as this cartoon. But this cartoon in your head helps get your brunt and get your mind straight, and so there's a lot of cartoons in our heads and I'm curious. What are some of your cartoons? Are there any that you go back to time and time again and so I'll give you some others, so this is another one that I've used a lot, there's different versions of this. This was actually an illustration that I had made for a lot of these.

In fact, most these illustrations that you'll see and we're gon na go through today are illustrations that I had commissioned for the book that I took down to Haiti to help teach young people about electricity in order. So they could, you know, do a little bit with solar, which was a lot of fun by the way. Haiti is a tough place right now, but this is this is one of those, and so when you think of you know, high voltage goes to low voltage. That's one of the basic rules that I always talk about, but this water tower metaphor kind of helps.

You visualize that difference. A high voltage going to low voltage current being the water flowing out of the water tower, the actual work being done on the waterwheel. Being the wattage and then, of course, you know, voltage being the the potential difference and in this case we're representing it by gravity. It's just it's just a metaphor: it's not perfect! You can pick it apart.

There's a lot of things about it that are incorrect, but it helps you get your head around voltage, amperage resistance. In this case, we've got a little nozzle here on the waterline that acts as the resistance, and then the work is actually what's being done against the waterwheel, and that would be your wattage and yes, my voice just broke up again Caleb, so you can go ahead And comment on that again: getting these sorts of these sort of metaphors in your brain really help with diagnosis, and I think, a lot of technicians who struggle struggle with electrical diagnosis. They don't have these cartoons in their head. They don't have these pictures that they can rely on, and this is just basics.

I mean this is just basic electrical, I'm science, but I think a lot of people when you go to school. You spend a lot of time focusing on the math. So there's a lot about Holmes law and how to actually calculate it, but the reality is: is that in the field very rarely do we calculate anything electrically? It's really uncommon for us to calculate them not saying ever do cuz. There are some cases where you do, but it's rare generally speaking, we're just taking measurements right, and so what we do in school doesn't necessarily equate to what we do in the field, but understanding the relationships does equate so understanding what happens when you change the amount Of work, you do what does that do to the amperage? What does that do to the current and then what is resistance to the current and how does voltage affect current? Those are all things that do matter to us, and so the relationship matters much more than the math and that's true with a lot of things.

It's even true in refrigerant diagnosis, a lot so I like to always start with the relationships. If you do this, then that happens as we call a if this is then that equation or or or logic, if this happens, then that happens and that's a good way to get started. And yes, I see all of your that's about how I need an air scrubber hahaha real funny. No, I am not sick.

I just happen to control my indoor relative humidity to a very low level, and so my throat is a little dry okay, which is why I've got my cranberry juice here and by the way. Even if I was sick, you can't catch a virus over a webinar, at least not that I'm aware Caleb says I need a gym. You know what Caleb I've about. Had it with you.

Alright, these I stole out of that same old book. I said the 30s but I think actually might have been the 20s and it gets to the late 20s. No vodka in my cranberry, my wife forbids spirits in the house now so I am. I am forbidden from any spirits in the house any longer.

She's, probably wise, so let's see here, these are actually illustrations that I had made out of that book, and these are really good ways of thinking about the difference between direct current, that's up here on the top, using a centrifugal pump driven by a pulley versus alternating Current and when we think about alternating current, a lot of people have really hard time getting their head around alternating current and how that works is you know which direction? Does it go, goes both directions. But when we see this, we understand that the energy in this case is going to move this piston back and forth. So the water is going to alternate back and forth in pipe, whereas here it's going to circulate, but either way we can accomplish the same amount of work. It's just gon na be back and forth in this one, and it's gon na be directional in this one.

So once you get this picture in your head, it's a nice illustration to show one time, but once you get the cartoon in your head, you don't get it out of your head and then now you always think of it. That way, and so in terms of diagnostics and how that applies to electrical diagnostics and understanding electrical, I think it's really helpful to teach these things in this way. So that way you can get that cartoon locked in your head. Not everybody is visual and I get that in fact, I'm actually probably less visual than some people, but most technicians are visual, most technicians when you say you're a hands-on learner when you're thinking about something that's happened in the past you're, actually accessing the visual parts of Your mind into having these sorts of cartoons in your head.

It can really help with that next thing. This is another example we're now we're equated water transmission, so moving water through pipes to electrical transmission, transmission and conversion generation transmission conversion in both cases. So we look at a you know: a simple water system: we've got a steam engine that drives a pump, it's generating the energy on one side and that it transit through the pipes and then it's converted on the other end to a water engine. Basically, a water motor, so we've got an Impala here and it drives on the other side.

Well, that's exactly the same thing that's happening here now we have a steam engine and it's drunk and it's driving a generator. So it's creating this rotational electrical field that creates an alternating current that then transmits over a distance over a copper wires and then it's converted via a motor, so the opposite generator and motor pump and motor they're both really the same thing. And so it helps you visualize that transmission and conversion side of things as well that sometimes can be hard for technicians to understand or newbies. I should say to understand that even technicians, though so again at this point, we're really just this is all Theory stuff.

This isn't really Diagnostics, but having this helps you quite a bit. Here's another one: how about for high frequency versus low frequency, another cartoon in the head, imagining grabbing a jump, rope and just bouncing it up and down. Doesn't it for me jump rope, could just be a regular rope, could be a hose, doesn't matter to people and the faster you go, the shorter the wavelength becomes, the slower. You go, the longer the label wavelength.

So we call this high frequency just means. How frequently are you shaking it up and down versus low frequency, you're doing it less often and in the case of what we do day in and day out with electrical? That's just the frequency that the motor is turning or the generator is turning. There were the power generation at the actual power company, the power plant. That's where your frequency starts is that's actually the rotational speed of the generators or the distance between the poles and the generators more specifically, but it gives you kind of a picture of what that is like, because we experience a lot of these things in regular life And it just helps you get your head around it all right here we go.

Anybody have any analogies that they, like anything that that pops in mind, because I have a feeling that I'm just gon na sit here and talk to myself for a while. So you always, you can always raise your hand, so Terry Miller just raised his hand. So I allowed Terry to talk and now, if he unmutes himself, we can actually talk to each other. So so far out, I have four people who are prepared to talk to me, but they haven't unmuted themselves and actually spoken to me and that's how that works, though.

So, if you want to talk to me, that's how you do it open or closed. I, like the analogy of the drawbridge for open or closed, because this is where water and I've talked about this a lot. But this is where the water analogy breaks down, because when we think of open to closing a faucet when you open the faucet water flows and when you close the faucet it Soph. Well, that's opposite of how it works with electricity, which is why I prefer the drawbridge the drawbridge when it's closed, it's a path that the cars can go over.

I often use cars as metaphors for electrons recurrent as well when it's open the cars can't move, but when we think of open and closed those concepts open and close, there's a lot of analogies outside of electrical. So you have yes or no. That's a that's! A boolean equation where the answer is either yes or no and electronics, it's one or zero, open or close, yes or no 1 or 0. Those are all the same concepts.

There's only two options open or closed, Joseph Davenport says I'm listening wish. I could see the PowerPoint I've tried every sitting. There is both here and on the website. Yes, all right, Joseph, I don't know what it looks like on your end.

Maybe somebody who has actually gotten it to work can can suggest that to you, but when you're thinking about things like relays or switches or contacts, all of that you could just as easily say yes or no, so you could say contactors closed. That would be yes. Contactor is open. That would be no contactors closed.

That could be one contactors open that could be 0. It doesn't doesn't matter so just a couple different ways to think about that and yes, I am touching my face. I know that's not allowed, but I'm at home. So I'm allowed to touch my face at home.

You know those are the rules, another couple of terms that are really important to understand short or open. When I teach classes, I always use the example. You know you have your grandma's television, when your grandma's television stops working or her stereo stops working. She says it's shorted, my television shorted and all that means is she's not actually saying that it's actually shorted that there's a low resistance, undesigned path, she's saying that's doing something that she doesn't expect, and so people have come to call short circuits anything that's doing something.

They don't expect, but a short circuit is actually a very specific problem in electrical diagnosis and it is an undesigned, low resistance path and it can be a nun designed low resistance path in between switch legs. This is one that's kind of a this is disputed territory, but I just use the common terms in our industry, so a good example would be if I have a short in between this yellow wire coming from my thermostat, which is the control circuit that powers my Contactor, this is a very simple one, but imagine that this yellow wire was shorted to the white wire. What would happen if the yellow wire was shorted to the white wire? It would also energize whatever the white wire was hooked to, so that could be the furnace that could be electric heat strips in the case of a heat pump and oh that would we would call that a short now kevin says: wouldn't that be a shunt, not A short - and that may be that may be a better way of saying that either way it's it's it's a connection. It's an undesigned connection.

I've heard it called a short. Quite often, Caleb says it's a short. I don't know it's just what I've always called it. So I always just sort of say it's an undesigned low resistance path.

So when you have a path between two things that aren't designed to have a path between them to me, that's a short now, an overcurrent, that's associated with a short. That's what blows your fuse, and so that's what we show here and in this case, why does the fuse blow the fuse blows? Very simply because we have this, you know we have our transformer here. Transformer goes into our fuse out of our fuse to our out of there to why and then it shorts to the other side of the transformer. So it's the same as connecting this to this, and we understand this intuitively, because if you connect a battery and you connect the positive negative side of a battery together, it shorts the battery out right you're, connecting from one side to the other.

You have unrestricted flow of current now in the case of a battery. This is actually where it gets interesting with batteries, and I had to learn some of this doing more solar with the battery. You have a limited power supply, so when you short out a battery, the battery goes dead right. You ruin the battery when you short out something like a transformer or the high voltage into your house.

You have a much more. You have a much greater power supply because ultimately, it's connected to all the way back to the power plant, and so in order to get it to shut off before it just melts everything all the way back. You have to have these overloads. You have to have these fusible links.

You have to have these circuit breakers, that break the circuit, so that way it doesn't damage the wiring and that's in this case, what our fuse does our fuses on the second area of our transformer. This transformer apparently has no primary, because I just left that out for the sake of simplicity, when we have this undesigned low resistance path, that's what causes the fuse to blow. These are all basic. But what I find is that people who struggle with electrical diagnosis struggle with these basic concepts.

If you drill back enough generally speaking, they don't have a solid picture in their head about the basics cuz. Once you build those building blocks, then all you need is repetition. I get people who ask me all the time. Hey, I need more experience.

I need to be taught how to read schematics and diagrams. So let me see here Eric says: just try. The phone app and the slides are showing up the slides might not work in a browser on a phone yeah that might be. That might be what it is I'm, but by the way, all of these diagrams everything that you're seeing here, because I'm getting a lot of requests for the diagrams all of them.

I have posted at one time or another on Instagram um. I don't currently have them all at one place, and the reason is is because I don't have my watermark on them. So if you want to find them one at a time, you can find them by going to Instagram and just looking back to the history and you can find them all and feel free to steal them from there. But I don't want to create a single file.

Repository of everything that I've created, because then next thing I know it'll show up in a book somewhere, not that I mind people using it, but you know how that goes. The point of what I'm saying here is is that when you drill back far enough, usually it's a misunderstanding of fundamentals that causes people to get stuck or they learn the fundamentals. And then they just don't do enough reps. Because, frankly, any of us who have who are pretty good at reading schematics - and I don't claim to be honestly - we think of guys who do a lot of commercial work and do it every day in and day out, they tend to be the ones who are Good at reading schematics.

Why? Because, in order to do commercial work on large complicated equipment you have to, you have to get a lot of reps in doing in reading schematics, and so they understand the fundamentals. And then they get a lot of repetition. And that's how you get good Francisco says Brian. I have a question regarding fuses.

I have a 30 amp fuse at 500 volts on a three-phase compressor. I've asked several people and still don't know if anything above 500 volts will also blow fuse, or only over amp situation. Ione ormally, you see 600 volt rated fuses. It's fine to use a voltage rating on a fuse on a fusible link that is higher than the rating of the old one.

So it's totally fine to use a higher rating on the voltage, not on the current. So you got to match the current exactly. But it's fine to use a higher voltage rating, because that's just saying that is the voltage at which, when you go over that it can actually bridge the fuse itself. So a higher voltage rating on a fuse is a better quality.

It's not actually there to protect the unit for for that higher voltage. Wiring diagrams are really big. Let's talk about opens now, so a lot of people will say that a short and an open or an open, a short most commonly that's most commonly what will happen because they start calling everything a short. But an open is a specific type of fault, and that is where there is no path.

So a short is a none designed path generally, a lower path that results in a overcurrent condition that blows a few strips to break or something like that. An open-circuit is a break in the path of some sort, so an undesigned break that results in things not happening. That should be happening and I always teach it this way, and I realize I confuse people more but I'll go ahead and confuse you. I used to say when you have a short something happens that should not be happening, namely blown fuse or some component being energized when it shouldn't be.

When you have an open there's, something not happening that should be happening, and the tricky part is. Is that a lot of times short circuits cause opens? A good example would be is that this is a short circuit, but once it blows the fuse now this is an open. So the short circuit causes an open, and the same thing is true of a circuit. Breaker right when you have a shorted compressor, the short causes the breaker to open in order to protect the wires I'd answer the question: there's some questions in chat about fuse types.

Yeah, you have to match the few step. I'm not saying that. I'm not saying that you can just swap in a different type of fuse, because you do have different times. You have slow versus fast.

You have different amperages, so you so I'm not telling you to swap it out with a different fuse in any significant way, but the actual voltage rating on a fuse that is a that is a rating that has to do with the point at which an arc Can go across it, so you can use a higher voltage and he's asking me it how much higher again most cases, they're gon na be very close, because they're gon na be the same general design. So it's gon na be rare that your all of a sudden gon na have some fuse. It looks exactly like another fuse. That's gon na fit that's gon na, be a significantly different voltage.

Let's talk about schematics, so one thing that's interesting is that when we get used to looking at ladder schematics after a while, we get used to diagnosing left to right and we start to think about electrical circuits in terms of left to right. That's kind of a mistake and it's something that happens actually with more experienced techs, sometimes because this is an alternating current circuit, so we have l1 here we have l2 here and then everything connects in between and in terms of isolating circuitry. That's helpful. Now.

This is kind of a modern ladder schematic or a ladder diagram. We're not everything is even left to right. The way it used to be, I mean a traditional one. You would have two lines and everything would connect in between and with a lot of manufacturers, especially in the residential side, are starting to go away from that.

But it is helpful when you first get started to start on the left and work. Your way to the right, but the reality is it's alternating current, so it's not like the electrons are moving from one side and just going to the other side and here's where this gets interesting. So let's talk about on this on this schematic here you have a what they call a adult. What do they call? This add a leg, the right terminal.

That's not the right term. My mouth is running much faster than my brain at the moment, so they call this a like a one plus contactor, and so you have your one, give your one set of contacts here and then you have the shunt, which is just connect it across and that's Why they say thank you to everybody, he's saying that, so that's why it says 23 and 23, because electrically these are the same points, which means that if you have this sort sort of system, you have l2 connected all the time. So l2 is connected. All the time, which means that there is potential present everywhere in the circuit at all times, even when the system is off but which side is that coming from it's not coming from this side, it's not coming from left to right, because if we think just in Terms of left or right: well, there we got an open, open contact right there, no it's coming from right to left, because this is the other side of the circuit.

This is a really interesting one anyway, but this is what happens. Is that a lot of technicians? They will take a they'll, take a voltmeter and they'll look to see if voltage is present and they will measure l1 and they'll measure l2 and what they'll find is or there, although measure somewhere in the circuit and they'll, find 120 volts to ground on both sides And they'll think that, there's you know in most cases, they're gon na they're gon na miss make up have a misdiagnosis because they're imagining that it's coming from this side when in reality it's just coming from the other side. Another interesting thing about this particular diagram, which is why I use it because it's it's a kind of a weird one. Is we also show here we have a crankcase heater and we have our crankcase heater switch, and so it goes through here through the crankcase.

You turn back here which is interesting, because how would that work, because it's both connected on the same side right? How would this ever energize I'll wait until somebody explains it in check or somebody who wants to raise their hand? How on earth would this crankcase heater ever energize, given the way that this is wired? Doug says it's a carrier, that's true, so they use magic. So the answer is Jason says it: it's only energized when it's off, so it's only when the contactors open. Well, how does that work? It works, because when this switch is closed, this is a good way. Cuz I'd like to talk about a a voltmeter as a voltage drop measurement tool, it's a way to think about a whole meter.

That's helped me a lot as I've gotten more cut more and more comfortable with a voltmeter through my career when this contact is closed. If I take a voltmeter and I connect one half of the voltmeter to 11 - and I hook the other half of my voltmeter, the other side of my voltmeter to 21 - if it's closed, what am I gon na measure? I'm gon na measure zero volts or there abouts. Why? Because a voltmeter is a voltage drop measurement tool. I'm not measuring a potential difference between the two, because, when there's a closed switch, there's very little resistance in between these two points.

So therefore, there's almost no voltage drop right now, if I open this switch now, what is the voltage drop between these two points? Well, now it's significant right because I have an air gap in between so I've got potential here. I've got potential here. There's an air gap in between that voltage drop is the entire voltage right, because now that resistance in this air gap is significant, it's a it's the entire. It represents the entire voltage, and so now I have 240 volts present across here.

Well, that's what this crankcase III uses, because now it acts as the path to get in between the two sides, so in actuality, what's gon na happen in this circuit, when this contact is open - and this is obviously still closed because that's just a shunt, what's gon Na happen is we're gon na have and again I'm trying it this left to right way, which is you know it's just silly, but because it's not DC, it's going both directions, but it's gon na come through here. It's gon na go through the switch it's gon na come through here and then it's going to travel through the compressor it's gon na go through the contactor and then back the other side. So this run winding is going to take the brunt of that now. Why doesn't the compressor start running? Why doesn't it overheat? Well, it's because this crankcase heater has a significant resistance, and so the answer is this run winding is actually going to warm up and that becomes part of the crankcase heater strategy.

It's not enough current for it to run the compressor, but it is enough to have a warm run winding because, if you've ever measured, the resistance on a compressor winding winding the winding - and this is one of my biggest pet peeves I see people do is they Will measure I'm going allows Tim dasta's EO to talk if he wants to so Tim, I'm allowing you to talk. If you want to unmute yourself feel free to join me: hey bro, hey there. You are you're the first guy to join me on this podcast, I'm so happy. I thought I was going to talk the whole time.

How's things, good man. How are you good? What do you want to know? I wanted to know something that you wanted to talk about related to electro. I was um held actually gon na answer. Your question that you just answered the power goes through the windings of the compressor, because the winding just turned into a conductor at that point.

You're not creating an inductive field and so you're winding. In this case you you know, you're run while it's actually all of them, but you're unwinding in this case is in the way that I just showed it it's acting as a resistive load. So it's essentially just a heater. You have a good way of do.

You have a good way of thinking of that like how do you? How do you describe these things if somebody I'll ask it this way, so somebody says to you: hey. I have a really hard time. Reading schematics cuz. I get that a lot.

How do you answer that question? What do you say to somebody Tim, muted himself again, fine, fair enough. I thought that was a public question. Others others can also. Others can also.

You know add in, but what are your thoughts? I mean, I think it's pretty much, how you explained it that current flows and everyone thinks that current takes the path of least resistance. And what we have to remember is that it takes all paths, and so it just depends on how easy that path is and you'll have the most energy or the most work. That's done. So if that easy path is a short circuit, a bare wire to wire short, then you're gon na get a lot of energy.

If it's not a very good path and you've got a lot of voltage drop across it, then you're not going to get a lot of energy at one place. But all those constants, like you said, are just important to kind of instill early on and then get them out there working on it. To actually have them read those readings as soon as possible, but they got ta have what you're doing here. Well, there you go, and I agree completely cuz you agreed with me first so then I agreed with you.

This is this has been just. This has been just lovely but yeah, but you pointed out what you pointed out was really smart about the parallel paths that this idea paths of least resistance, because this wasn't in my slide - and I wanted to mention this. When people say electricity takes the path of least resistance, no, it takes all paths of sufficiently low resistance. That's one caveat that I will add, because the do electricity take all paths.

Well, no, because I mean an air-gap is technically a path that could be bridged, but isn't because the resistance is sufficiently high that no electrons actually move through that path. But when we're talking about things like electrical circuits, if there is a path, then electrons are going to move across that path, they're going to move across it proportional to the resistance in that circuit. So you look at resistance. You look at voltage.

That's gon na tell you how much current is gon na move across that path so left to right. You sell yourself short when you do that when you only think in terms of left or right, because in a 240-volt circuit, it's also coming from right to left. So another thing is: is that when you have run whining for example here, then you have the crank case heater. The reason why the run winding doesn't really get that hot is because your windings in your compressor are actually pretty low resistance and I've had this happen.

A bunch of times so I've mentioned this in several podcasts. So forgive me if I've already said this so many times when you have, when you measure a cross from leg to leg, on a compressor so say you measure from run to start and then start to come and run to comment. Those are going to be very low resistances. In some cases, those resistances will be so low that your meter will actually rain when you're measuring leg to leg, and that doesn't mean that your compressor is always gon na draw these ridiculously high currents.

Because if you work Ohm's law, it will look like you're gon na. Have these you know 100 amps, whatever that's only what it draws when it starts once that compressor gets moving and you get that inductive reactance, that's additional impedance is what we call it. It's additional resistance, electrical resistance that shows up once that motor starts running once that inductance kicks in, and so the problem is this is this is where rubber meets the road, a lot of technicians, they will measure from leg to leg and they will see these very Low resistances and they will think that it's failed, especially if they use something like one of those mega meter things and they connect leg. The leg, that's a misunderstanding of how those things are supposed to work.

Those are all ways to go to ground, and so, when you're checking from short for shorts, you're generally checking the ground. Now man, this happened the other day with a very smart technician who works for us. We had a situation where he was using a meter, very good quality meter and he measured from leg to leg and he checked the Copeland specs and he saw that it was measuring lower than what the Copeland spec said. So then he said it was failed.

The problem was: is that a lot of meters even pretty good quality ones when they get below an ohm or in that range there? They get kind of inaccurate, because it's such a small measure, and so he was seeing a lower measurement than what Copeland said. But it was just his meter. His meter was just showing a lower ohm reading than what the what the manufacturer specs said, and so he condemned the compressor. The compressor was not bad, so leg to leg shorts or something you got to be really careful with diagnosing, because you have to understand your meter.

You have to look at the specs from the manufacturer. Generally speaking, we're gon na find short circuits by measuring to ground. Not by measuring from leg to leg, and frankly I always use it. What we call the redneck test and the redneck test is, is that once you get done confirming that you think it's the compressor, that's shorted! Well, then, isolate the compressor start it back up and see if everything else runs without the compressor connect, and that gives you an indication.

We don't condemn compressors in almost any application, because they say that they're bad on a meter, if they're not actually drawing over current. In real life, so again you bird did a bird did a video on that. That's a that's a good example of that michael says: unplug. It question mark yeah, so disconnect the compressor.

If it's a plug. Well, it's just a plug, just disconnect it. If it's you know, terminals take a picture of it, so you know how they go back on. Take the wires off.

I don't take him off at the contactor Michael says: take him off at the contact or no, I take them off at the compressor. I take them off at the compressor, I tape them up and then I put everything back together and I start it back up and if everything else runs - and it was before it was shorted out, it was tripping a breaker and now everything else runs well now. I've isolated the problem down to the compressor, which this is the number one way that good diagnosticians diagnose is they do isolation and Confirmation versus just using a meter saying it's bad and then moving on. You always have to confirm at the actual device isolate and, if possible, use other parts to replace, to even check and make sure to double-check.

You know this is where, when people who work on big facilities, this is how they do it, they're not being parts changers by just verifying checking against checking against checking making sure that it is that part before you condemn something and say that it's bad, throw it In the trash right to always double checking - and this is where even and I use jumper wires more often than I even use meters in a lot of cases - it's very difficult for me to give a lot of examples of this because it happens in real life. So often the situation's vary so much that you run into so you touched on something and it kind of got me thinking so on this diagram. You've got a single pole, contactor I've seen technicians, they find a bad contactor and they replace it and say. Well, I don't have a single-pole contactor.

I've got two full contactor and that's always better than a single-pole contactor I'll, throw it on there. Well in this case, if they do that their crankcase heater will never energize. Am I correct correct? Yes, if you do it that way, your crankcase heater will never energize and really the only right way, and this application is to use either that sort of the same sort of contactor or to shunt out one leg of your contactor. So you can take one leg of your contactor and just connect from top to bottom, with a big piece of wire and and that will that will essentially shunt that leg out, but again, sometimes that requires double logging or whatever.

So in these cases this is the one rare case where it really there isn't another way around. That, for example, train had a version of this, but it wasn't. It wasn't the same sort of situation where they would just connect to the bottom side, but it wasn't feeding through the compressor winding. I would have to test it.

I don't know for a fact, but if you took this and if I instead of connecting it in this way, if I just hooked it from here and then over to the other side, so that we would be energized actually no, that wouldn't that wouldn't work trying To think here, yeah, no, the only right way to do this would be by shunting out one side. That's really the that's really the only way, and again I don't even know if I want to tell somebody to do it that way in this case yeah. That's a lesson, two texts that you may be going back behind. Another technician you may be putting on the fourth contactor and the lifespan of that unit um.

It might be a good idea just to check the wiring diagram and make sure that you're putting on the right style of contactor before you just put on what was already there yep absolutely - and this is actually something we've talked about a lot in the past when These, when those were more common, because that's not actually stock on most units, even that come with that wiring diagram, that's sort of a generic wiring diagram and that's a they have a little star that this may exist. You don't see that in the field, as often as you once did, and so it's not as big of a deal, but there was a time when that was actually quite common. That is, that is an issue and you have to pay attention to those details. Alright, so voltage drop measurement tool.

I'm gon na read this line because it's a confusing line, but once you get your head around it, I think you'll find it really helps. You be a better diagnostician think of your volt meter as a voltage drop measurement tool. Okay and we've talked about that before, but here's the line the voltage drops across east each resistance or load, whether designed or undesigned in the circuit, is proportional to the percentage of the total circuit resistance. That load represents.

I'm just gon na tell I'm gon na tell you a story to help. You get your head around this particular phrase here, rather than because I could draw it on a circuit and start throwing numbers at you. But if I throw numbers at you, a lot of text check out because we don't think in terms of numbers. If you look in the book, the books gon na show you different home ratings for different loads and that's how they teach it, but think of it.

This way, okay, so I've got a circuit and it's not working right right and I find that I have a bunch of resistance in a loose lug in a disconnect, there's a loose lug in a disconnect, and so it's carbon DUP. It's been arcing and so now there's additional resistance in that loose lug right. We get our heads around that there's additional resistance. Am I gon na measure a voltage drop across that way? I will now it might not be significant, but if I measure a voltage drop across that whatever voltage drop, I measure is proportional to the percentage of the total circuit resistance that load represents.

So this teeth is really simple. I have an arced up terminal and I measure 24 volts of drop across that arced up terminal on a 240 volt circuit. What does that tell me that tells me that 10 percent of the total circuit resistance is in that terminal. Let's make it even more simple.

Like we said before, if I go back here - and I measure 240 volts from here to here from terminal 23 to terminal 11, I measure 240 volts. That tells me that a hundred percent of the voltage drop in this circuit right now is present between those two points, and that makes sense. That's why you measure nearly the fully applied voltage across a load right, if I measure between common and run right between common and run, and this contactor is closed. What am I gon na measure gon na measure 240 volts or there abouts? If 240 volts is present from here to here, I should measure about 240 volts from here to here.

Why? Because nearly a hundred percent of the total circuit resistance is that exist from here to here is present from here to here. If this had 10 % voltage drop in it, then it would also have 10 % of the circuit resistance and vice-versa I'm interested to see. If that makes sense to anybody, does anybody who's like that either they don't get that at all? Let's see if I have any hands any hands raised, so I've got a couple hands raised. I'm gon na I'm gon na allow we got Chris Roseberry, we got Michael Makara, we got freon man.

Any of you want to want to comment on that. You just unmute yourselves Jamie says no use number well, I did. I did use numbers and it still didn't make sense, so normally how they would show it is, they would show multiple loads in series, and so they would teach this as a series circuit. The thing is: is that most circuits we work on are in series, let's see so somebody somebody's talking who's here me hey, free on man.

What's going on, how are you Brian, very good, very good, who is this? I'm Jim Landry and I own reliable refrigeration in Boston sweet. Are you unlock down right now? Well, we're not on lockdown, but they did suspend permits on three of my jobs. Is that good or bad? It's discipline you get to work without them, checking up on you, because that sounds good. No, no! No! No! You can't work at all.

No okay! Well, that's the wrong direction. That sounds yeah. That is the wrong direction. Absolutely! So what are your thoughts? I was a girl.

Why couldn't talk most of the time, so I apologize. Okay, okay, this is my first time. I've ever actually went to a live webinar all right, so I got your email a while back and I signed in I downloaded zoom, and Here I am so yeah. Well, you know I look at your thing every day at night and all that you look at my thing every day, a night that sounds if he yeah tech tips, yeah I'm with yes, sir okay.

Well, thanks for being here all right, no problem who else? Who else we got here, Chris yeah, how you doing good good? What's going on with you, you know I just want to share a story with you now had the other day, all right, let's hear it, you know family and start. The compressor was home and looking at a capacitor fan side is bad right. So tell the homeowner: hey pastures, bad, i hook it up. The breaker was trip reset.

The breaker went outside push the disconnect in and breaker trip begin. So, of course you know most of Thomas is a compressor issue. Unplugged the plug go back in reset the breaker come back out it tripped again and long story short. The fan was actually shorting out.

You know the whole unit and tripping that breaker, which was a first for me because most of time the fan doesn't, you know, have enough to trip that, but uh yeah it is. It is more uncommon on residential equipment to find condenser fans shorted to ground, and you know why that is. I mean I, like I said I took everything out thought it may be been the contact. It took all the wires off and you know I don't know why that happened.

Like I said that was my first interaction in 15 years. Any any motor can theoretically short out, but condenser fan motors are much less likely to for a couple reasons. One the forces at play aren't as great, and so you don't have as much torque going on, but secondly because the gap in a condenser fan motor is air and a compressor. You have that that whole thing is full of refrigerant and you have oil and you have everything else.

So when you have a you know some sort of catastrophic issue in there where something breaks off and goes flying around and banging around it's much more likely to cause a consistent to ground short than it is in a condenser fan motor. So there's a couple different reasons, but yeah you'll definitely find condenser fans. It cause shorts more in larger commercial applications where you have greater forces at play and that sort of thing but unrest attention it is. It is a little bit more rare, but good, find and that's isolation, diagnosis.

What you did there was isolating and kind of walking down the line until you figured out which component it was, which is in my book a totally acceptable way of doing it. Also, my brother thanks for joining me. Yes, sir, I'm not gon na spend a lot of time on this particular phrase. The voltage drop measurement tool.

Either you get it or you don't here and I'm not doing a good, very good job of describing it because every time I describe this one, it's hard for people to get their head around, but I guess to sum it up. We mostly work on parallel circuits, and so that means that you have only one load in the path between the two sides of your circuit, so in the case of a 240 volt circuit that would be between l1 and l2 in the case of 120 volts. That would be between l1 and neutral in the case of 24. That would be between hot and common right, and so each one of those circuits.

Parallel paths only has one load, and so, when we measure across the load we're measuring generally a hundred percent of the voltage drop because the or nearly because almost all the resistance is going to be in the load. The case of you know, let's use an example. Presser would be the compressor windings in a contactor on the Y circuit. That would be the contactor coil right, so you'd measure 27 volts or whatever it is across the contactor coil.

But if you add another voltage drop in parallel or in series with that parallel load. In that same path, then, that voltage drop depending on what percentage of the resistance is that's going to be what percentage of the voltage drop it is, and so this is how we can use our mirrors to find things that are undesigned or connectivity whatever, and we Can use our meters to find problems in the circuit and it's also helpful when you're diagnosing it overly complicated circuits and you your meter on it and you measure some weird voltage. What are you measuring you're measuring the voltage drop between those two points? You can say potential difference, that's fine, but a meter is always two leads in you're measuring between two points. If you're using a voltmeter next thing is you know, I always want people to look for the obvious.

I can't tell you how many times - and I use this - this is another image that I made for the for the folks in Haiti. How many times it's just the simple things that people do wrong where they wrap it: the wrong direction. You know around a terminal or they use a you know they take stranded wire and they wrap that around the terminal and the stranded wires coming off all over the place rather than using a crimp on terminal or they make a crimp on terminal incorrectly or they Leave a bunch of bare wire exposed, or you have wires that are crossing one another. You know we're crossing a discharge line or rubbing out on a piece of metal there's a lot of different things that are just obvious.

I'm diagnostic know knows that an experienced technician keeps their eyes open for that a newer technician often will miss and from a diagnostic skill standpoint. That is a really invaluable skill and also you know just never allowing these little details to just you know pass by the wayside. Double logging is a really big one where people take multiple wires and jam it underneath a lug or you're, not getting good connection, and so all of those things can add resistance to the circuit, which can then cause problems because it causes voltage, drop. Additional resistance causes voltage drop, which is part of what I was describing there.

It's the same thing when you, you know when you have a switch that starts to get carbon up, but like a contactor that can add, voltage, drop to the circuit and cause problems. Kevin says so far no air quotes, but we got a rub out. Yes, that's true, I always do air quotes but see now now, if I do air quotes, you can see me and so that kind of ruins it, and I do talk a lot about. Rub outs and it's not a dirty thing: it's just what happens when a wire rubs out on a metal part and when they love each other very much, they create other little wires, breakers, overloads and wires.

This is a we're gon na get we're gon na finish up here on one of my favorite things that I now you guys are, just being you guys are just you you're crossing the line over there in chat now breakers, overloads and wires. Water sizing is super important. It really is very important, but it's really misunderstood in all segments of the industry, so not just by air conditioning and refrigeration technicians, but also by electricians, because wire sizing is not as simple as this chart right here. So this chart here shows 14 gauge 14 amps, 12 gauges, 20 amps, 10 gauges 30 amps.

These are all based on sort of worst case scenario. Applications using, I think it's. What is it 60 degrees Celsius wire, which is what nm is nm means nonmetallic? That's what we call romex trade name, ro max right, and so when we're used to working in residences - and they have that 60 degree Celsius, insulation on them or it's row max. This is where these sizes come from, but also this is copper.

This isn't aluminum. So there's a lot of different variables that factor in here and there's also some D rating variables, meaning there's some cases where, if you're running through very hot areas, then you have to de rate for that lots of different factors. But the one thing that's sort of a saving grace for us in our industry is that the manufacturers give us on the data plate what we size the breaker to and what we size the wire to believe it or not. And if you follow that as an air conditioning contractor you're, safe, you've done you've followed proper practices, and so, let's use an example here.

This is actually a pool heater now I know I'm good. I know I'm gon na do this and everybody's like cuz. This is one of these like really disputed things out there in the industry, but trust me do your research. You will find that this is the case.

Minimum circuit ampacity, amperage capacity of the wire. This is what you size your wire to. So you find a wire that the NEC says and there's a lot of factors: okay, so I'm not gon na give you all these factors, but if the NEC says that it can carry 40 point to one amps under the conditions that you're in wire length, isn't One of them, by the way, that's when people will always say, is that the length of the wire is voltage drop. That's actually not one of the factors that the NEC requires you to consider.

We won't go into why that is, but it's it.