Our Attendees Demonstrate What They Learn – 2025

🧊 What Is a Filter Dryer and Why Is It Important in HVAC?

Want to know what a filter dryer does and when to replace it?
In this brief demonstration, Comarsh Lunan from HVAC Second Chance University explains what a filter dryer is, where it’s located in an HVAC system, how it works, and why it’s essential for maintaining system performance. Whether you’re a student, technician-in-training, or curious homeowner, this overview will help you better understand this small but critical component.

Transcript – Filter Dryer Explanation by Comarsh Lunan
Hi there, good afternoon, good morning. My name is Comarsh Lunan. I’m here with HVAC Second Chance University, and I have this component in my hand — it’s considered to be a filter dryer.
A filter dryer is normally found in an HVAC system, similar to this component, which is the condenser unit. Their typical location would always pretty much be on the liquid line — this line right here, which is the smaller line. It would be somewhere right here on the liquid line.
Now, we’ve got different kinds of filter dryers. This one in particular can go with a heat pump. It has a flow on either side where the reversing of the refrigerant can go either way. On a straight cool, we have filter dryers that only go in one direction.
Its prime reason for being in the system is basically to restrict impurities that you normally find within the system. It restricts and catches moisture from the system, and it also restricts particles like contaminants and acid.
With proper use, it helps preserve the unit and give it a longer lifespan. The cooling efficiency will also have more longevity.
The filter dryer is a very small component, but it actually works like an air filter. You’re basically filtering out the things that cause impurities and malfunction in the system.
You really want to replace these guys whenever we make, for instance, an upgrade to the system — when we’ve gone in and cut the system. Once the system is open, it’s always good practice to replace the filter dryer, just in case, so it can filter out any contaminants we might have accidentally let in.
That’s pretty much the life and operation of a filter dryer.
Thank you.

💡 Understanding AC Capacitors – With Danny from HVAC Technical Academy

Curious how to detect a faulty AC capacitor?
In this hands-on explanation, Danny from HVAC Technical Academy walks you through the purpose of a capacitor, how it works in your condenser unit, what signs to look for when it’s malfunctioning, and how to properly test it using a multimeter. Watch the video above — then review the full transcript below to reinforce your learning or share with others.

Transcript – Capacitor Overview by Danny
Hey, this is Danny. I’m with HVAC Technical Academy here, off of Lake Mary Boulevard, and today I’m going to explain the purpose, use, and ways to detect malfunctioning capacitors on an AC unit — I prefer, specifically, a condenser unit.
So basically, here we have a condenser. We have the capacitor that’s located right here next to the contactor. And this particular capacitor has a rating of 80 on the compressor side, 7.5 on the fan side. It gives you a 5% plus-or-minus range — so that gives you a little leverage on the actual capacitance.
Ways to find or detect damaged capacitors can be bulging in the capacitor, capacitor leakage, or cracks. If you see cracks in the capacitor, that means it’s not good. It can cause a problem with your AC functioning properly.
So basically, a capacitor really just stores energy for a quick start. It can act as a temporary power source. It smooths out functions in voltage and in current. So that’s just basic functions and purpose of it.
We’re going to go ahead and test the capacitor real quick here to see if we have a good one. And by doing that — okay, so on the capacitor, you have a two-prong, three-prong, four-prong, okay? This is a dual capacitor. So basically, the four-prong is the common port — that’s the one that goes to the contactor. The three-prong is your HERM, and that’s the one that goes directly to the compressor. Your two-prong goes to your blower — blower fan, blower motor.
So we’re going to go ahead and test that. In order to test it, you would take the reading from microfarads — that’s what it’s based on — and you would put your multimeter, that’s what I’m using, to test it. I have it on the microfarad meter setting.
I’m going to go first and test for the compressor portion of it. So I’m going to take my common port, and I’m going to take the reading on the HERM. And we’re getting a 79.5 reading on that.
Now to test for the fan — still use the common port — and then we’re going to go ahead and test on the fan portion of it, the fan port. And we’re getting a 7.37 reading, and that’s pretty much well within the range of what’s required for this capacitor to function.
And that’s pretty much it — the whole function, the reasons why it would go bad, and so forth.
So again, I’m Danny. I’m with HVAC Technical Academy here off Lake Mary Boulevard, and thank you for your time. I hope this really helps to explain how the capacitor works, the purpose of it, and some things that could go wrong within your system.
Thank you, and have a great day.

🔧 Thermostat Terminals & Float Switch Basics – With Cisco from HVAC Technical Academy

Wondering how a thermostat connects to your HVAC system — or what that little float switch really does?
In this short video, Cisco from HVAC Technical Academy (aka Second Chance University) walks through the basic thermostat terminals, explains their role in powering heating and cooling functions, and breaks down how the float switch protects your system from leaks and overflow. Whether you’re learning HVAC for the first time or reviewing core concepts, this quick overview can help.

Transcript – Thermostat & Float Switch Overview by Cisco
How’s it going, y’all? This is Cisco at HVAC Technical Academy, aka Second Chance University. Today we’re going to go over the basic steps about our thermostat, how our float switch works, and the terminals connecting to the thermostat.
So here we have a thermostat. If you look on the back, we’ll be able to see the terminals, and this is where our low-voltage wiring connects up to. Just to give you some basic steps on what each terminal means —
R is our 24 volts, which is going to give us power to the system.
G is our call for the air handler blower motor.
Y is going to be our call for the condenser fan motor.
O is going to be our reversing valve that energizes in cool mode — so all of these first terminals are when you have a heat pump that energizes in cool mode.
Now, when you have a heat pump that energizes in heat mode, we’re going to go to our B, which is our reversing valve that energizes in heat mode.
Then we’re going to have a W — sometimes there’s a W+, W1 — just W is our call for the heat strip.
W-E is our call for the emergency heat.
And then we’re going to have W2, which is our call for the stage two of the heat.
All right, so those are just the basic steps, terminals, and what they mean.
So now we’re going to go over to our float switch — this little device right here. We’re going to help you understand this a little better.
The float switch is pretty much something that you add into your 24 volts to make sure that, just in case there is either a clogged drain line or the pan from the evaporator coil fills up due to freezing — like when the evaporator coils freeze — it will fall, and it can fill up the pan.
So in that sense, when those things happen, this little float switch device is going to turn off the system to make sure that nothing else continues to keep leaking or any of those types of things.
Hopefully that helps you better understand the terminals on the thermostat and exactly how this little float switch device works.
Thank you, it’s been nice knowing you guys — and, uh, Cisco out.

🔧 How to Replace a CFM Fan Motor – With Jose Vera from Second Chance University

Not sure how to safely replace a CFM fan motor in your HVAC system?
In this straightforward step-by-step video, Jose Vera from Second Chance University walks through how to remove and replace a CFM. He covers essential safety precautions, which wires to watch for, and tips to help you avoid mistakes — like taking pictures before you disconnect anything and not losing your screws.

This is a great primer for HVAC students and techs in training who want hands-on clarity about replacing fan motors and handling capacitors safely.

Transcript – CFM Replacement by Jose Vera
All right. My name is Jose Vera from Second Chance University, and I’m here to explain how to replace a CFM. So basically, before you do anything, we have to make sure the power is off.
And then after you shut off the power, you have to discharge — uh, you have to come in here to the capacitor and make sure the capacitor is discharged by using a flathead, right? And you’re going to cross it around, touching each other.
Once you’re done with that, you will need — then you have to take a picture very quick, see how all the cables are and where they are located. Unless you have experience doing this for a long time, I would just make sure — pictures at this time will be your best friends.
After you’re done with that, you can just pull out the cables that are coming from the fan, which in this time is the brown, yellow, and the black one.
Okay, so I’m going to show you by taking these off exactly what I’m talking about. Do not lose the screws — I always put it into the pack there.
You see the cables that I’m talking about — it’s the black, yellow, and brown. So I’m just going to pull this out, right?
Right after I disconnect them — and yellow is coming from the contactor. All right.
Okay, now that I have this out, turn this around, and we’re going to take the blade out.
Sometimes this gives you a hard time, but this one was easy to take out.
Place the blade the same way you took it out so you don’t forget — you don’t want to put it backwards.
And then after that, you’ll be taking out these screws right here, right? In order for you to take the fan motor out.
So I’ll be using, at this point, a 5/16.
All right — oh, I got the wrong one. It was the one that I had on before. It’s actually a 7/16.
All right, and that’s off.
And once you take that off — okay.
All right. And that’s how you replace a CFM with a new one.

🔁 HVAC Refrigerant Recovery Process – With Justin Rivera from Second Chance University

Need to understand how to safely perform the refrigerant recovery process?
In this step-by-step walkthrough, Justin Rivera from Second Chance University and HVAC Technical Academy demonstrates how to properly set up and operate a recovery machine, connect the hoses, monitor pressure, and safely transfer refrigerant into a recovery tank. This process is essential for every HVAC technician learning proper system handling and EPA-compliant practices.

Transcript – Recovery Process by Justin Rivera
How you guys doing? My name is Justin Rivera. I’m here with Second Chance University and the HVAC Academy. I’m going to show you how to do the recovery process today.
Right now, I’m in recovery mode. So, to be into the recovery mode, you’re going to end up hooking up your vacuum hose. Make sure they’re closed at first. Once you hook them up, you can turn on the machine, open up your manifold on the high side and low side, open up your vacuum suction, and you will be in vacuum mode at that point.
And now, to do the recovery process, you will need a recovery tank — a 410A tank. You make sure it’s a proper tank for the machine and the rating of it. This is a recovery tank. You would obviously have it plugged in — it’s not plugged in at the moment because I’m in vacuum mode right now.
You would plug in your inlet to your manifold, and then the out would go to the out. Once you start that process, you would press start on the recovery machine. You open up the valve. You make sure you have the refrigerant side open, your manifolds are open on the high and low side, and then it will start sucking in all the refrigerant into this machine.
With this machine, you scale it out. It’s rated for about 80 pounds. I already have about five pounds of refrigerant in here.
When you’re putting the refrigerant in the machine, this part of the machine gets hot. You cool it down with the hose. When you cool down the machine, it allows the pressure of the machine to go down, and it recovers faster that way.
Once it’s about 7 psig, you don’t have to cool it anymore because it’s already low enough that it doesn’t need the coldness from the water to go into the recovery tank.
It’ll beep about one or two times. It’ll chime at you. You’re in the recovery mode. You close your valve. You close it off. You close this valve. And then you self purge.
Once you self purge, it’ll go for about less than five minutes and then it’ll also beep at you. Once it beeps at you, you close it off and then you can start your vacuum mode — which I’m in right now.
All right, my name is Justin. Thank you guys for listening to my video.

💨 Understanding the Pump Down Process – With Lucas Circelli from HVAC Technical Academy

What is a pump down process, and why do HVAC techs use it?
In this fast-paced, practical explanation, Lucas Circelli from HVAC Technical Academy and Second Chance University walks you through the pump down process — what it is, how to do it, and why it matters when working on an evaporator coil or replacing parts like a TXV valve. Learn the step-by-step method to safely isolate refrigerant into the condenser so you can service the system properly.

Transcript – Pump Down Process by Lucas Circelli
Hey there, my name is Lucas Circelli. I’m here with HVAC Technical Academy and Second Chance University. I’m here to explain the pump down process to you.
So basically, what the pump down process is — we’re going to isolate the refrigerant into the condensing unit, into the condenser coil, and all of that within the condenser.
The way we do that is by shutting off the liquid line service dials. That will allow all of the refrigerant to be sucked in through the suction line into the condenser.
As soon as we have that one closed, we have to start really going at it on the other one and closing it real fast. So we’ll go ahead and do this.
Make sure you have your gauges set up so that you can read the pressures as they go through. You really got to go fast on this.
You should start seeing your pressures go down as soon as it starts getting closed. There we go. So your pressures start dropping real fast. You’ve got to get over here and start closing your suction line.
You’ll start hearing your compressor start to get upset at you and start groaning. Once it gets down below — starts really getting mad — you’ve got to shut it off.
You have to do this quickly so that you minimize the amount of refrigerant that gets pulled into the line set.
The reason you do a pump down is so that you can work on the evaporator coil. You can take it out to clean it, replace a faulty TXV valve — anything basically from your service valves to your evaporator coil.
Any of that maintenance is done with a pump down.

⚡ What Is a Contactor? – With Pat from Second Chance University

Ever wonder what a contactor does in your HVAC system?
In this short and practical video, Pat from Second Chance University gives a simple explanation of what a contactor is, how it works, and how to spot when it’s going bad. Whether you’re starting your HVAC training or want a refresher on common system components, this is a great beginner-friendly breakdown.

Transcript – Contactor Overview by Pat
Hi, my name is Pat, and I’m here in Second Chance University.
Today, what I’m holding is a contactor. I’m just letting you know what a contactor is, and a little bit about its job, and how you can find out when your contactor is becoming faulty — and yeah, that’s about it.
So, this is a contactor. It’s actually like a big electronical switch. It has different circuits.
Okay, down here is your high voltage, and on the side is your 24 voltage — so that’s right here and right here.
When this presses down, you can hear that click — that is going down. You have different circuits depending on what it’s calling for.
So let’s say it’s calling for the top here — this will isolate and become a 24 volt. And yeah, so you have your 24 volts and your high voltage.
So this is a switch that has an open and shut, and the way that you can know that something is going on that’s out of the usual is when it stays down. So it’s just giving circuit — it’s just energizing, energizing, energizing.
You come out, you’ll be like, “Oh, I have a little dead lizard in there — it’s stuck.” So you just remove it, and if it’s still working, it’ll go ahead and energize the circuit that you’re looking for to energize.
Do you replace these? Not very often — but you can, and you will. You won’t like try to re-mend or fix this — you would just go ahead and buy. They’re not that expensive.
So, yeah — this is a contactor.
And my name is Pat, and I hope it was helpful.

🌀 What Is the HVAC Vacuum Process? – With Pete from HVAC Technical Academy

Ever wondered what the vacuum process is in HVAC and why it matters before charging a system?
In this lighthearted but important explanation, Pete from Orlando, representing HVAC Technical Academy and Second Chance University, walks through the vacuum process used to prepare a residential HVAC system for refrigerant. Learn what a vacuum really is, why 500 microns matter, and how to safely complete the process with the right tools.

Transcript – Vacuum Process by Pete
Oh hey, hey there. Hi, my name is Pete from Orlando here at HVAC Technical Academy.
You’re probably wondering what I’m doing here — that’s a good question. I wonder myself! But it’s a very important step. Today, we’re going to be talking about vacuum.
You’re probably wondering, what is vacuum? That’s a good question — because I myself was wondering the same thing.
So what we have here is a residential system where the refrigerant was recovered and placed into a recovery tank. This is a recovery tank right here.
We then connected a vacuum machine — which is this unit right here. This is going to provide a negative pressure into the system to allow a vacuum process to take place.
But what is a vacuum process? That’s a good question. A vacuum process is basically a process where we are extracting certain elements and non-condensable gases, moisture, and other possible contaminants within the system — to make sure that the system has a clean and smooth transition to accept the refrigerant when it’s time for recharge.
But you’re wondering, “How long does that take?” or “When do I know that the vacuum is ready?” That’s a good question.
The EPA regulations state that a minimum measurement of a vacuum in a system should be no more than 500 microns or less. So 500 microns is the measurement for a vacuum.
On this system right here, we’ve reached that level of vacuum, and now we’re getting ready to stop the vacuum.
So follow me as we show you how we do that.
Basically, our machine is on right now. I’m going to go ahead and turn the machine off by hitting this button right here.
Then I’m going to rapidly close this manifold gauge. Then I’m going to disconnect my vacuum hose.
And I’m going to rapidly place my vacuum hose on the manifold retainer hook.
And now the system is ready to accept refrigerant.
Processes like this and much more can be found on the HVAC YouTube page.
Again, my name is Pete. I am from Orlando and I am very proud to come to Second Chance University’s HVAC program.
I hope you enjoyed this video and look forward to more exciting news and videos in the future.
Thank you very much.

🔥 What Are Heat Strips? – With Yelanie from Second Chance University

Trying to understand the difference between heat strips, straight cool, and heat pumps?
In this short and practical video, Yelanie from Second Chance University explains what heat strips are, how they function differently depending on your HVAC setup, and how to check for continuity using a multimeter. Whether you’re learning HVAC basics or troubleshooting a heating issue, this is a great place to start.

Transcript – Heat Strips Overview by Yelanie
Good morning, I’m Yelanie. I’m at Second Chance University, and today I’ll be teaching you about heat strips — what they do, the difference between a heat strip and a straight cool and a heat pump, and how to test for continuity.
Your heat strips would be located on the top of your air handler. The purpose of your heat strips in a straight cool system is that when you call for heat, your heat strips blow hot air through here.
On a heat pump, you have a reversing valve which reverses the flow of refrigerant — and it’s more cost-efficient. It’s cheaper to have a reversing valve inside of your AC system.
The way you check for continuity when the heat strips are out is:
First, you’ve got to put your multimeter on ohms. You’ve got to check that right here. You want to check your thermal fuse from one side to the other — you can hear the beeping. Again, continuity there.
I don’t get continuity from here to here, or from here to here, because obviously they’re not connected to one another.
But that’s pretty much it.
Thank you.

Hi, my name is Adel, and I would like to explain the metering device and what it does.

How the Metering Device Works

Okay, there’s a sensor bulb, and it goes over here, and the sensing bulb goes over here.

What happens is:

• When the compressor releases high-pressure liquid, it flows into the metering device.
• From there, the refrigerant slowly flows through, with 80% liquid refrigerant and 20% vapor.
• The sensor bulb detects the temperature.
• If everything is working correctly, the refrigerant turns into 100% vapor before going back to the compressor as low-pressure, low-temperature vapor.

Since the compressor doesn’t take liquid refrigerant, the metering device is essential for controlling the refrigerant flow and ensuring that only vapor reaches the compressor.

How to Test if the Metering Device is Working

If you’re not sure if the metering device is working, you can test it by following these steps:

1. Remove the sensing bulb from the system.
2. Place it in hot water.
3. Check the pressure gauge:
   • If the pressure on the gauge doesn’t move, that means the metering device is bad.
   • If the pressure changes, the metering device is still good and working properly.

Final Thoughts

That’s the reason for the metering device—it controls the refrigerant flow and ensures the compressor only gets vapor.

Hope this helps! Thank you!

Hi, guys! This is Alisia with HVAC Technical Academy, and today I’m going to be talking about a condenser fan motor.

What is a Condenser Unit?

First off, I just want to show you guys what a condenser unit is. This is the outdoor unit of an HVAC system—the outdoor condensing unit of the HVAC system.

This is what houses the condenser fan motor.

What Does the Condenser Fan Motor Do?

The condenser fan motor turns the blades just like this. But inside, it pulls air across the condenser coils, circulating air around the condenser coils.

It condenses high-pressure, high-temperature vapor into a high-pressure, high-temperature liquid.
This process transfers heat from the refrigerant system.

So, that’s pretty much what a condenser fan motor does.

How to Tell if Your System is in Cool or Heat Mode

Right now, this is a non-operating condenser unit, but if it were running and you placed your hand across the top, you would feel it blowing out hot air.

That is an indication that your system is in cool mode.
If you place your hand on top and it is blowing out cooler air, that means your system is in heat mode.
Types of Condenser Fan Motors

This right here is an Original Equipment Manufacturer (OEM) fan motor.
This one is a universal fan motor, meaning this one will cost a little more than the OEM.

What to Check When a Condenser Fan Motor Goes Bad

These fan motors do go bad. If yours stops working, the first thing I would check is the capacitor, because replacing a capacitor is much cheaper than replacing the entire condenser fan motor.

And yeah, that’s all about an outdoor condenser fan motor!

Have a good day, guys!

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Hello, this is Arthur from HVAC Technical Academy, and they’ve invited me to give you some basic knowledge about capacitors.

We see two here right now—this is a dual capacitor, and this one here is a singular capacitor. Since this one has a lower microfarad (MFD) rating, you will see that logically, as you begin to understand this, it is measuring for the fan.

This one right here is a dual capacitor because it is dealing with both the fan and the compressor.

Where Will You See It in the System?

This is a heat pump, and you’re going to see the capacitor right here, basically in the corner.

Capacitors come in different sizes, but what you want to focus on specifically is the microfarad rating (MFD).

To put it as simply as possible:

• The 70 MFD is always going to be dealing with the compressor.
• The 7.5 MFD is going to be dealing with the fan.

How to Hook It Up

When you install and hook it up, as you see here, these plugs are labeled so that you can understand where the common wire goes to the fan.

Testing a Capacitor

Now, I want to share with you a little about testing, not operation—just testing to see if it’s in operative mode.

• When you buy a capacitor from the store, you always want to test it first to make sure it’s effectively operative.
• If the measurement is not according to the 70 or 7.5 MFD, it could go over by five or under by five, and that’s acceptable.
• But if it goes below five in the measurement, using this clamp meter, then there is something wrong with the capacitor.

Signs of a Bad Capacitor

You will also see trouble with the capacitor when it is bloated out—more than likely, that means the capacitor has overheated.

• If you see a bulging or balloon-like top, you’ll know this is a bad capacitor.
• What do you do? You have to replace it with the same microfarad rating (e.g., 70 or 5 MFD).
• Some capacitors are 45+5 MFD, so you will need to match the measurement you need.

Quick Test Process

• You are going to use this device (meter) and start from Common to Fan.
• Check the measurement here for microfarads (MFD) while it is not in operation.
• When you test Common to Fan, you should see 7.5 MFD—if so, it’s up to par.
• Then, go back to C and Herm (Hermetic)—hermetic means the compressor is hermetically sealed.
• If you see 70.5 MFD, that is acceptable because it can go over or under by five.
• However, if it goes too high or too low, something is wrong with the capacitor.

Final Thoughts

So, that in a nutshell is the most basic way to test a capacitor to see if it’s in operative mode.

Again, this is not about operation—when you install and connect it, that’s a whole different ball game.

• You’re going to be using clamps to measure voltage and amps, and that’s a different lesson for another class.

Hopefully, you guys enjoyed this—it’s basic information that you need to know.

If you’re in an HVAC class, especially at HVAC Technical Academy, they’re going to test you on this, so it’s important to have some basic understanding of capacitors.

Thank you guys for listening! I’ll catch you some other time—maybe I’ll be teaching something else like a compressor or something.

Have a good day!

#VacuumSystem
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Good afternoon, you guys! My name is Christopher H., and I’m at HVAC Technical Academy.

Today, I want to talk about this little device right here called the reversing valve. The reversing valve is located on the outside of the condensing unit. You can probably find it around here, but it can vary depending on different unit types.

Understanding the Reversing Valve

I would recommend learning refrigeration before getting too in-depth with the reversing valve because it’ll give you a better understanding of what it does. But to make a long story short, a reversing valve is what reverses the flow of refrigerant.

• If you’re in cooling mode and switch to heat, it’ll basically switch the cycle around.
• This means it’ll put your cool side where your heat side is.
• If you can see this—and if you’re not color-blind, you feel me—just follow the arrows and see how everything flows.

What it does is reverse the refrigerant flow back and forth through these tubes.

How the Reversing Valve Works

To go more in-depth:

• Refrigerant goes in through the top and comes out through the bottom, distributing it through the other parts of the refrigeration cycle.
• Inside, there’s a shifter that you can’t see, but that shifter moves the refrigerant left and right.
• What makes the shifter move? Pressure.

The Role of the Solenoid

That pressure comes from this smaller device right here called the solenoid.

• Basically, what you see here is what’s inside the reversing valve, just in a much smaller form.
• When the solenoid is energized, it sends a pressure signal back to the reversing valve, making it shift left or right.
• And like I said, all it’s doing is reversing the flow of refrigerant to match the setting you have it on.

So, that’s basically what a reversing valve does in short.

My name is Christopher, I go to HVAC Technical Academy, and I gotta thank Danny, gotta thank everybody, and of course, thank you guys!

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Hello, my name is Desmond, and we’re at HVAC Technical Academy. I’m going to tell you about your compressor.

An air compressor is a pneumatic device that converts mechanical power into compressed air, which can be used to power your outdoor condenser unit.

Where is it located?

It is usually found in the outdoor unit of your air conditioning system, either on the side or at the rear of the house.

How does it work?

The compressor squeezes refrigerant gas molecules together, which increases the refrigerant’s temperature and pressure.

Also, this is the heart of your unit. If you need to get it replaced, in most cases, it would be better cost-wise to replace the whole unit rather than just the compressor.

Thank you for watching! Anything else you need to know? Ask Google!

That was quick—okay, let me make sure.

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Hello, guys! My name is Jorge, and I’m here at HVAC Academy. I’m going to break down what nomenclature is.

So, here we have a Carrier unit condenser, and the main things about your nomenclature are your model number and your serial number.

Understanding Model and Serial Numbers

First off, the model number is going to give you the type and size of your unit. The serial number is going to give you the year and week the unit was manufactured.

For example, let’s look at the serial number on this unit. It reads 0218, followed by other letters and numbers. What does 0218 tell me? It tells me that this unit was manufactured in the second week of 2018.

Now, moving to the model number, I try to look for the big numbers. This one reads 25HCC5 4883. I stop at 48—what does that mean? The 48 tells me the unit has 48,000 BTUs.

To calculate the tonnage, you divide 48,000 BTUs by 12,000 BTUs:
48,000 ÷ 12,000 = 4
This tells me that this is a 4-ton unit.

Another Example: A Lennox Unit

I want to show you another unit over here—this is a Lennox.

Looking at the model number, I find 60—this tells me that it has 60,000 BTUs. To determine the tonnage:
60,000 ÷ 12,000 = 5
This means this is a 5-ton unit.

Now, looking at the serial number, I see it says 11919. What does that tell me? It tells me that this unit was manufactured in the 19th week of 2019.

One More Example: Another Carrier Unit

I want to show you one more unit—follow me!

Looking at this Carrier condensing unit, I check the serial number. It starts with 1N15. Again, what does this tell me? This tells me that this unit was manufactured in the 19th week of 2015.

Next, I go down to the model number and find 30. I assume that means this is a 30,000 BTU unit. To calculate the tonnage:
30,000 ÷ 12,000 = 2.5
So, this is a 2.5-ton unit.

Final Thoughts

If you’re not familiar with nomenclature, take a picture of the label, Google it, and it will tell you exactly what the unit is.

Thank you! I’m Jorge from HVAC Technical Academy.

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Hi, my name is Monique, and I’m at HVAC Technical Academy. Today, we’re going to be talking about the thermostat—what the letters stand for, what it does, and how it operates.

I’m going to take off the covering of the thermostat right here. It has the letters that indicate how it functions and what each one does.

• R – 24 volts, which is the power
• G – The blower motor
• Y – The contactor that calls for the condenser motor fan
• C – The common, which is the ground
• O – Reverse valve
• If it’s a heating system, it will have:
  • B – A heat pump that energizes in heat mode
  • W – Heat strip
  • W/E – Emergency heat
  • W2 – Stage two

Testing the Thermostat for Power

To test if your thermostat has power, you’re going to check R to Y, which calls for the condenser motor fan on the outside. If it’s not working properly or if there’s no low voltage on the contactor, that could indicate a problem.

That’s all I know for now about thermostats. I hope I gave you enough information.

Thank you!

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All righty, hello there! My name is Pedro, here at HVAC Technical Academy, and I will be showing you guys how to test a transformer and how one works.

So, this right here is a transformer. As you can see, we have two—one right here and one right here. The reason we have two in this system is because, let’s say, it’s for a two-story house. This transformer right here will be controlling this zone board.

How a Transformer Works

A transformer has two legs of power—120V, which bumps up to 240V on the transformer. Then, it bumps it down to 24V for things like your thermostat relays, boards, and other low-voltage components.

How to Test a Transformer

To test it, we grab our multimeter and set it to VAC. I’ll set it here so you can see.

• Then, we’ll grab our two leads (two prongs) and place one on Common and one on 240V.
• As you can see, we’re getting 242V—it’s okay to get a little over or a little below, but not too much.

Now, we’re going to test our low-voltage side, which would be the other side for things like our thermostat.

• You would go to the back side, put a probe here, and another probe right here.
• As you can see, we’re getting 27V—that is good!

And that, ladies and gentlemen, is how a transformer works and how to test it.

Thank you!

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Hello, my name is Stephanie, and today I’m going to tell you how a contactor works and how to test one.

As you can see, in this case, we’re looking at the condenser, and the contactor is located here, which is usually found in the casing that covers the capacitor and the U contactor, where the high voltages come in and everything.

Okay, so before you test anything, you definitely want the power off—you want to be safe, okay? Sometimes that can mean power on or power off, but in this case, since this system isn’t connected, we’re going to learn how to check it with the power off.

What Does a Contactor Do?

First of all, the contactor allows the electricity to pass through and power whatever device or wire the thermostat calls for.

For instance, if we need to turn on the fan blower motor, this bad boy here will click in, allowing the energy to pass through, hit the capacitor, and the capacitor will start and run whichever device the thermostat called for that has to do with the condenser, in this case.

How to Test a Contactor

Usually, when you test a contactor, you want to test it in Ohms, all right?

If you don’t know what Ohms are, you can take a quick look at this thing right here—our metering device. I always say look for the one that looks like the horseshoe. You see it there? Zoom in—little horseshoe—all right?

To test it, set your sticks on your machinery condenser, and you pretty much want to place your point on the little screws here—on the bottom and the top.

Do it this way—you’re not going to get anything, okay? So, you want to do it here and here. This is basically checking for continuity.

And when you press this in—uh-oh, what happened? There you go! Switch over! Sorry about that.

When you press this bad boy in—there you go—I gotta stick it on there, you guys!

As you can see, this contactor works. CU, you’re hearing that hum noise because the energy is now flowing through. It’s not—It is now—It is not.

This side is the side that has the part that basically does not transfer the electricity all the time.

But as you can see here, this side does not have the push-in device, which means this side always has continuity, all right? Because it’s always going to be providing power.

Final Thoughts

Want to know more information about a contactor? Google it!

But overall, those are your basics.

Thank you!

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Hey everyone, Breezy here from HVAC Technical Academy! Just a quick reminder—learning to use tools properly in the lab is just as important as practicing safety while doing it. New attendees are getting hands-on experience with essential HVAC tools, all while following the safety guidelines that will keep them and their team protected on the job.

Remember, safety isn’t just a rule—it’s a habit that sets you up for success in the field. Keep practicing, stay sharp, and always put safety first! See you in the lab! 🔧⚡ #HVACTechnician #HVACTraining #SafetyFirst