I wanted to talk about something that you may have seen before, but just help you understand a concept and that concept is ghost voltage, so who's ever heard of ghost voltage before anybody. No, it's holy ghost voltage. Okay. So when you hear ghost voltage, what do you think power? Can you just be quiet for a second okay, okay, ghost voltage? What do you think of like remnants of voltage? That's sure, okay, that sounds about right, yeah, just not ready to leave a voltage that just isn't ready yeah.

Is it okay, yeah it makes it makes it makes a ghostly noise. No, so ghost voltage um the way i would define it is it's it's a case where you are picking up a voltage, you're measuring a voltage, but that voltage doesn't actually do any work like you can't get it to do anything, and so an example would be You're measuring 24 volts somewhere, but as soon as you go to energize the circuit, then that voltage disappears and so kind of to start with the easiest way to think about this would be um. Imagine that you have a a you know: water pressure on your house and you don't have any toilets running. You don't have any hoses running.

You don't have anything like that and you put a pressure gauge on one of your hose bibs and you measure the water pressure on your house. That's what we call static pressure, it's a version of static pressure. It means that there's no dynamic flow. Nothing is actually moving and you'll measure a pressure, but the minute that you start to actually move the water, the minute that you, you know, run a tub or you run a shower or whatever.

Now that pressure drops, i mean you all, have experienced this. Where you've got two bathrooms in the house, two people are taking a shower. The water pressure drops right, it's kind of the same concept here, but but imagine that you're measuring a pressure, you're measuring a voltage, but the second that you go to use that voltage. It just disappears on you completely right it just or or not necessarily completely, but it doesn't it's not capable of doing any work.

So that's what we call ghost voltage, it's where you're measuring something, but then, when you go to use it, it's not there anymore, and this starts by just understanding how your meter works. So your meter is actually a load. Your meter is actually taking the voltage in one star, taking current in one side and actually creating a path through the circuit, so you're actually wiring your meter in as if you're wiring, in a light bulb when you're measuring voltage right. But your meter is a very high impedance load and impedance is just another fancy way of saying resistance.

It's all the different types of resistance, it's a very high resistance load and so across your meter. You will see voltages that that only are there because of that very high resistance. As soon as a lower resistance load comes into place, and now you actually have current flow now now it disappears, and rather than talking about it, super fancy terms. Let's, let's, let's look at it from uh uh from a more basic standpoint, there's a couple different things that can go on here if you've got a wire and it is being energized.

So, let's imagine um maybe never thought about this before. But if you have a a transformer, so transformer symbol, i always like to kind of draw the symbols for things. Is this let's see here yep, that's not the correct number of wraps but and that's a really bad transformer. But when you energize the primary on a transformer, so we're going to say we energize it with 240 volts, but this circuit is open.

So we're going to say we're just going to draw a switch here and it's open and then we have a load. Maybe it's a contactor coil whatever - and this is 24 volts here right when we energize the primary on this transformer. Does the transformer draw any current when the secondary is open any current? No well? How is that possible? Because we have 240 volts applied across this coil here. How is that possible? How is it possible that it doesn't draw any current? The voltage isn't moving.

Oh, it is moving. Oh wait. You better believe it's moving it's alternating current, so it's moving back and forth 60 times per second 60 hertz right. This is connected to 240 volts through a coil.

If you, if you ever listen to a transformer, even when nothing's running. What's it sound like that's the ghost and the transformer yeah it makes it it'll make a little hum right, you'll hear it humming. If you feel it, you can feel a little bit of heat there right and that's true, even if you don't have uh any load on the secondary, even if there isn't any current moving through the secondary right. This is called excitation current.

That's the fancy name for it. I had to look it up because i didn't remember exactly what it was. I wrote down this piece of paper, so i can remember it um and it is kind of a cool word. I mean, let's be honest, excitation current, but it's very small and that's because you have this back electromotive force.

You have this uh inductive reactance that that occurs in the secondary um. Where, basically, it's just you know, it's moving one direction, but then it's just going straight back to the source again um, so there isn't a lot of current moving on. But there is this initial excitation current. So if i took and there's a there's, a video on this uh, we'll link to it in this video uh by veritasium, where they talk about like this theoretical circuit, that's basically the width of the entire universe and there's all this interesting stuff.

But a lot of the ways that we imagine that electricity works is wrong. Okay, so we imagine that electricity is like you know, just trains moving down a track. You know you've got these electrons and they're just moving one direction or some people will say it's like a tube full of ping-pong balls right and you push one ping-pong ball on one end and another one falls out the other side, but really what electrons are is All of these infinitesimally tiny uh particle slash energy units that, when we are moving electrons through a conductor, they're happening really erratically, and it's just on average we're creating this motion. But what's creating the motion is something called a sine wave which are just these just these waves that exist these circular waves that come off of a wire and so within a transformer.

That's how we can convert from 240 to 24, because we have this uh. This electromagnetic field that we're intensifying by all of these wraps, so these sine waves are an electromagnetic field. Okay - and i know this is getting kind of weird here, but i'm going to explain why we're talking about this. So let's say that we have a wire.

That's running through a conductor running through a unit and it has 240 volts applied across it, and then i have another wire and - and this is in this wire is connecting to something. So it's you know it's connecting over here and it's going to a compressor, winding or whatever, and that compressor is running, and so there's this there's this field, but now i run another wire next to this wire and it cuts through these this electromagnetic field. That wire is going to actually pick up a little bit of voltage. There's going to be there's going to be a slight potential difference.

That's picked up in that wire, and so it's going to cut through these these lines and we're going to get a little bit. Have you ever taken a meter and you're measuring and you just measure these, like weird small voltages, you know one volt here, two volt here, whatever often that's what this is okay, and so this is called induction. So it's what happens when the same thing that happens in a transformer when we go from the primary and we induce a current in the secondary, we can do the same thing by running two wires next to each other. This is why you don't take low voltage wires and run them right next to high voltage wires.

This is why, especially with more complicated control systems, you have to be really careful about that, and you have to be careful about grounding and all that stuff, because you'll get these induced voltages that mess with the controls. It's. Why, like on some of these high-end communicating systems after lightning strikes, you'll get these weird faults, and that kind of thing i get this in my house all the time. It's one of the reasons.

It's not the only reason, but it's one of the reasons why that happens, because when you have a lightning strike, there's a lot of magnetic electromagnetic sign going on it's traveling through the whole house and that's picked up in those conductors and it gives the controls weird Signals you guys follow that. Does that make sense? Okay, so the idea that electrons move through wires, just because you're kind of bumping one electron into another is not really true. We use those kind of theories we talked about it like flowing like water, but really it's more like there's these electromagnetic shepherds that move along the outside of a wire at the speed of light. It's these! It's this force that exists on the outside of the wire that moves electrons through the wire.

It's that external electromagnetic force that moves electrons on average from one side to the other side. Does that make sense, and the reason why that matters is because that's how a transformer works? If that wasn't the case, the transformer wouldn't work, we wouldn't be able to transmit a potential difference through open space, because that is what we're doing now we have these. You know we have these plates of metal and all this, but at the end of the day, our primary and our secondary and a transformer are not touching one. Another they're not physically in contact, there's a lacquer that insulates them from each other, and the same thing is also true in a capacitor right.

The two sides of a capacitor do not touch each other. There's this. You know basically plastic sheeting with a metal coating on it and one side doesn't touch the other side. But yet there is a motion of current in and out a potential difference across that capacitor and it's because of the same force that electromagnetic field that exists.

That's why that can work, but that's only one reason why we see ghost voltage so again, the point being that one of the reasons we see ghost voltage is when we run conductors next to each other. If you've ever taken like uh a microphone cable for uh, you know doing video or you've taken a video camera or your phone and you're videoing and all of a sudden you'll get like this weird buzz and you'll notice that you're near something that's high voltage. I do i have this a lot with my podcasting i'll have a one of my microphone. Cables will run next to a power cord for my computer and all of a sudden you'll get this you'll get this weird buzz, and that's because i mean you won't get a buzz, the buzz will occur and it's a whole different thing, and that's because you're running Your microphone cable next to that high voltage power line, and it's picking up that 60 hertz that um 60 cycle noise.

That hum one lesson is we don't want to run conductors next to each other uh, especially high voltage and low voltage conductors, especially control conductors. We don't want to run them in the same. You know through the same hole in the cabinet. We don't when we're running them inside of a inside of an assembly.

We don't want to lay them next to each other. We don't want to take wires and wrap them back and forth with just a bunch of extra and jam it right next to high voltage, because you're going to get that induction. So one of the sources of ghost voltage is induction when you use some of you. May have meters that do this, but they do make volt meters that have what they call a low z mode.

Has anyone ever seen that seen that it'll say low z and that's a mode of measuring voltage where, rather than using a very high resistance load within the meter, it uses a much lower resistance? Z means impedance, which is just again another way of saying resistance. A very low z, low, impedance path through the meter and that causes these ghost voltages to disappear, because when you have this lower resistance load in the meter, now those don't show up because they're not going to actually be able to power that load in the meter. But when we're using our typical voltage meters, this is one reason that we see it, but there's another reason why we see ghost voltage and it's actually a more common reason and you'll see this sometimes, where you'll be like you'll be measuring outside with your voltmeter, we'll Draw a really basic, a really basic circuit here, so we're going to call this our y circuit. All of a sudden, i forgot how to draw y.

This is our y circuit. I know it gets weird. Sometimes it's early all right, and then it goes back over to common, we'll draw a switch in here. This is our thermostat call for cool right when there's a when there's a thermostatic call for cool the temperature increases causes the switch to close, which then energizes our contactor coil right and our contactor coil is connected in between y and c.

Now, if i take my meter, my voltmeter and i measure from here to here, i would expect that i'm going to measure 24 volts right and if this switch is open, of course. Well, in this case, and if this switch is open, i'm not going to measure anything. But if i close the switch - and i measure 24 volts across that. But then as soon as i close that or sorry when it's open, i measure 24 volts.

Let's say: let's say i take this wire off of here and i measure yeah, but that's 24 there, but when it closes, this is actually y here, and this is r. That's the problem with my illustration here: i'm measuring 24 volts here i energize the circuit and then all of a sudden it goes to zero volts. It disappears on me. My voltage disappears when i go to actually use it, and this happens because i have some sort of additional resistance in the circuit.

So it could be that past the contactor i've got a poor connection. There could be a wire nut here and it could be connected, but that connection could have something like you know: 200 ohms in it of resistance, and i'm not going to bother doing the math here, because you're never going to do the math. I have a whole article that covers ghost voltage if you want to go through all the math and how that all works, but in cases where you have really high resistance, it's just like having the water system in your house with a big kink or a big Clog in the main water line, when you're not using it when it's static, you're going to measure that full pressure. If there's no faucets running, there's no, you could pressure.

You got the full pressure because it's able to make it through and back up, and you see that pressure, but the second that it becomes dynamic, and you start to use it. The second that we close this switch, and now we energize the contactor. Now it disappears on me and again there is still going to be flow. There is still going to be motion, but that voltage drop is significant because the voltage drop exists across another point and it could be before or after the coil.

It doesn't have to be one or the other, because it's all a single path and so you're creating another series load, and so the voltage drop exists across the point of highest resistance and normally the highest point of resistance in an electrical circuit would be the load. The designed load, but if you have a really bad connection or you have a thermostat, that's got something wrong with it, where it's not creating a proper path within the thermostat right. That's going to become a higher resistance load and now you're going to have significant voltage, drop and you're not going to see that full current across across your load. The way that it's supposed to be when it's energized so again the point being that the difference between static and dynamic static, meaning what you measure when it's not doing anything dynamic, is what you measure when it's actually energized and you're intending to use it and what You would do in this case when you see that weird ghost voltage that disappears on you figure out where the actual issue is in the circuit.

There's going to be some sort of poor connection and what you can do - and this is this - is something that a lot of us have learned. You can actually take something like because it's not always going to be the contactor coil. This is just a single example. You can actually use something like a contactor coil or a relay coil, basically in place of a meter that can become a low z meter.

Imagine if you take the coil on a relay a 9340 or a contactor. You connect two wires to it and you use that to test the system pulls in. You have 24 volts, doesn't pull in you don't have 24 volts, that's basically a low z, volt meter, because your volt meter in these cases just becomes ineffective when it's not energized. If that makes sense, it's kind of a confusing kind of a confusing topic, but both of these things are cases where you see voltage and it's not able to do work and just knowing that that exists is going to make you kind of second guess yourself.

Sometimes before you make that call to sam or burt and say i'm measuring voltage, but it's not doing anything just recognize just because you're measuring voltage when a circuit is not fully energized when it's not doing any work. That doesn't mean that there's not still a problem. So in many cases what we do is we'll take a you know, we'll take a thermostat wire off outside and we'll start measuring the wire and we'll see oh well. You know it should be working, because i have voltage here where's, where it's supposed to be, but once you start to use it, then it doesn't doesn't do anything.

It doesn't do any work wires running next to each other. That's induction situations where you have undesigned high loads, bad connections, whatever that's caused by voltage drop and both of those cause, ghost voltage, one being because you're creating a small voltage, the other being because your voltage is too small because of too much resistance. Any questions not my best work here, but that's okay, that's great! Those are really hard problems to find so practically when you're looking for them. You don't automatically know often that the power is dropping out as soon as you get the call right once you know that part you've pretty much solved it, but what happens at first is it just looks like you're going around testing things, but when you try to Run it it's not working right and it takes a while to realize that i have voltage right up till the second, that a certain thing calls and then that drops voltage, correct, correct and another thing, and that's the reason why, if you've ever seen a therm thermostats Where, when there's a short, this is actually another reason that i didn't cover.

But you don't see it in this way in the same way that we're discussing here, if you've ever had a thermostat where you got to shorten the system, and it will go through time delay and as soon as it goes through time delay. It just goes back in time, delay again and it just stays in time to lay forever have you anybody ever seen that happen before well, the reason why that's happening - or you know at least theoretically my theoretical reason why it's happening is that when that it energizes That load and that load now has a very low resistance. There's a big voltage drop in that case as well, because, through the switch gear of the thermostat, it's designed to handle a certain amount of current when you get this big in rush of additional current there's. Also, a voltage drop, and so it basically just throws it because the voltage drops so much it just throws it back into time, delay again and starts all over.

It's not a design. I used to think it was a design feature like it was supposed to do that. But it's not it's just it's just because it's losing power because of this huge inrush of current. That's that's occurring! So if you ever see a thermostat doing that where it won't come out of time, delay it's because there's a short and so disconnect the thermostat and go through that kind of isolation, testing to figure out which conductor or load is shorted thanks for watching our video.

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