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Bryan explains how to read schematics/diagrams on HVAC equipment and walks through an example. He takes a Rheem air conditioner and compares the physical unit to its point-by-point diagram and ladder schematic.
Point-to-point diagrams illustrate how each component is wired in a piece of equipment; these tend to keep the same orientation as the physical piece of equipment. Conversely, a ladder schematic illustrates the current flow from one side of the circuit to the other (for example, from L1 to L2). Ladder schematics generally show the high-voltage side on top and the low-voltage side on the bottom.
Although diagrams can vary by manufacturer, there are typically a few consistent components. One of these is the presence of optional components on a point-to-point diagram. These components are NOT installed from the factory and are generally indicated by some variation of (OPT) on the point-to-point diagram. Field-installed components are connected by a dashed line, and factory-standard components are connected by a solid line.
All diagrams will have notes and a legend or component code to help you interpret the schematic. The legend will help you make sense of the abbreviations you see in the schematic. (For example, it will tell you that “CCH” means “crankcase heater” or that “CHC” means “crankcase heater control.”) Notes will give you information about acceptable connections and other relevant information for wiring the equipment.
On a ladder schematic, you will be able to determine the number of poles and throws of a component by looking at the diagram. A single-pole, single-throw component can only open or close. Squiggly lines underneath a component indicate a thermal switch, and a bell underneath a component indicates a pressure switch. A ladder schematic may or may not indicate the colors of the wires. If a ladder diagram does NOT show the colors, you may need to consult the point-by-point diagram.
A point-to-point diagram typically abbreviates the wire colors, so you may need to check the legend or notes. (For example, “R” may mean “red,” and “BK” may mean “black.”) Point-to-point diagrams may also indicate the placement of additional parts that would also be installed with optional components, such as wire nuts.
In short, ladder schematics show WHAT is connected, and point-to-point diagrams show HOW components are connected. The legends and notes exist to help you understand both diagram types.
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Hi, i'm brian with hvac school in this video we're going to do a walk through of the electrical components and an electrical schematic on this rheem air conditioning system. This is just a practical way, especially for newer technicians to get used to looking at schematics. I get a lot of people who ask me: what's the best way to learn how to read diagrams and schematics, and the answer is: is to just do it yourself and go through them slowly, but i'm going to kind of show you what that looks like for Those of you who are newer to the process and maybe feel a little overwhelmed by it. I wanted to open this up to show you the tests that we do for safety to make sure that we don't have voltage applied, and what i found was is our high voltage wire coming in on this side is all corroded.

That connection needs to be completely remade, probably go ahead and just replace the disconnect, because you can see how overheated and melted this is. This is black, so we're going to actually go ahead and replace this at a later time. This is just from our office unit, but let's confirm here that we have voltage on our outside poles and we do 213, because this is a 208 structure, and then that means we, because our disconnect is pulled. We should not have voltage here, but also as a safety check, we're going to check from each side feeding our unit to ground as well.

So i'm measuring from each leg to ground as a safety check and then coming in. We can see, we have power applied and this definitely needs to be addressed. The reality is sometimes these diagrams aren't legible. So this is when you would use the model and you would pull it up online in order to trace the diagram as needed all right.

So here we show the diagram, and this is where i want you to get comfortable, is in reading diagrams and schematics. Now, there's you know some people call it a point-to-point or a pictorial, generally they're, going to call this a point-to-point where the manufacturer tries to keep everything in generally the same orientation that it is in real life, whereas this they're generally going to call a ladder schematic And so a ladder schematic actually sorts everything in between the two sides of the circuit. So we talk about this all the time where current has to move in between two sides of a circuit. You can't have any opens, and so on this side, they're showing the high voltage side um, they could be present in the condenser and then down below they're, showing the low voltage and that's pretty standard.

If it had a transformer in it, then they would show the transformer symbol here, but because the condenser doesn't have a transformer in it, the only wiring that's coming into it. Is this yellow and brown that's feeding the low voltage of the contactor, also on this side. Here on the pictorial side or the point-to-point diagram side, they're, showing that a lot of these things are optional, so you'll see here, it says: optional, opt here. All these are optional.

All these pressure switches, the start relay, is optional. The start capacitor is optional, so pay attention to that, because a lot of these things you're not going to see in the piece of equipment that you're working on and specifically the one we're showing, is a very basic piece of equipment. Let's start by looking at our field wiring, so in our point-to-point we have these three dashed lines. One goes to l1.

One goes to l3, which is the other side of the contactor and the other goes to ground and that's our green. So whenever you see dashed lines, that's an indication of something that's going to be field wired, so even on a lot of these optional devices, you would have to field wire these in on the standard side of something that's not optional. You're going to see these two, these are our low voltage, our low voltage brown, which is our common and our low voltage y, which is our hot. Now again, this whole time delay circuit and all that this is all optional and you can tell when you go over here.

That's where you're going to see that all this is optional, our low pressure control, our lpc. If you look down here at our component code, lpc is our low pressure control, our hgs, which is our hot gas sensor, our hpc, which is our high pressure, control or high pressure, cutout control. And then, even on the high voltage side, we have a crankcase heater and a chc, so our crankcase heater is cch and chc is our crankcase heater control, which this system also didn't have. So a lot of that is just going to be things you have to identify: let's go through some of the basics, we'll start over here on the schematic diagram that shows it connected in between the two so you're going to notice, for example.

The first thing you see is chc in cch, crankcase heater and our crankcase heater control. Our crankcase heater control is a single pole, single throw switch, meaning it's only open or closed, and it opens on rise. The way that this looks where it's kind of a squiggly line underneath this is a thermal switch. So if this crankcase heater control is a low enough temperature, then it will make the circuit and allow our current to move through our crankcase heater.

So that's how that would be wired, but we don't know by looking at the ladder side or the schematic side that that is optional. You would have to actually look over here and see. Okay, this is optional, and even here it's showing the areas that wire nuts would be installed. So again, the ladder schematic is more simple for electrical diagnosis, it's easier to see what path is being taken, but it doesn't have some of the details also you're, going to see here that it doesn't have colors on this diagram.

Now, a lot of times a ladder schematic is going to have colors, but on this one it doesn't. You have to actually go over here to see what color these would be so r and bk, which is black. If you want to know what the different color codes are, it also lists that, right here in the wire color code, once again, even our next circuit here it has our start relay. It has our start capacitor.

Those are also optional, but one thing that isn't optional is the fact that we have a compressor coming out of l1 through t1, which is what we call our plus one side of our compressor contactor. It's the part that just has a solid line across the contactor that goes into the c terminal of our compressor, which is going to be a black wire, and you can see that if you come over here the same connection, you can see it's a black wire. Our r is going to go to the other side of the circuit. This is what we call the run side and in this case, the side that has the contact that opens and closes that's what we're going to call the run side.

It's fed by one leg of power coming from the utility one leg of 120 volts, then that feeds through goes to the run side. Our start side is a little different. Now again, this wire doesn't exist because we're not using any of the start gear. Our start relay or our start capacitor don't exist, so this is just going straight to the herm terminal.

This here is showing it as h. We want to see what color that is we'd come over here, we'll see that our start is purple. Our run is red. Going to the run side and our common is black again, we can trace these out from our contactor and we can find our purple, which is our start, our black, which is our common and our red, which is our run, which comes off of that top run Side what i call the run side of the contactor, then if we want to take a look at our electrical terminals, i usually find the easiest way to do.

This is just take a screwdriver go in from both sides like this, a flat blade screwdriver, and now we have our common, which is marked as c up in here. We have our run, which is red and our start, which is our purple so inside this compressor there are two windings that connect to this common point and also directly behind this terminal is where our internal overload is. So if our motor overheats in our compressor, it's going to open up to shut it off to protect it now, we're also going to see when we go over to our capacitor. Our capacitor has three terminals.

It has h or herm, f or fan and c, which is our common terminal, and our common common terminal on this capacitor is going to connect to two different things. One is going to go to the run side of our outdoor fan motor. Now here it doesn't even list any terminal names, but if we go over to our fan motor over here outdoor fan motor we can see that fan is a brown wire, and that is actually doesn't say that here. But that is our start winding on our fan, because it's the one connected to the fan terminal on our capacitor.

We have o, which is the run winding. If you look at o o is orange, it connects to common, which then is also jumpered over to our contactor. So those are these two wires, and you can see here. This doesn't really show exactly how they're connected it just shows that they are connected when you get over here.

It's going to show specifically where the wires are connected and what the colors are all right. So here we have our contactor, which runs our condenser fan and our compressor. If we look carefully, we can actually see the contact points are currently pulled in and they're in pretty bad shape. The reason they're pulled in is because we pulled the outside disconnect, which doesn't cut our power to our transformer.

So we've got our two high voltage lines coming in from our disconnect. We've got our ground, which is our green. These are what we call field connected wires and these are going to show us dashes on the diagram. These are our low voltage.

They come from our thermostat through our air handler, and these are literally just common and 24 volt y that pull our contactor in off the top of our contactor. We have a black, a red orange and another black one of the blacks. The larger one is going to go to our compressor, which is our compressor common. The other one is going to go to our fan, which is our fan common.

We have this purple wire here, which goes to our compressor start winding, and then we have this brown wire, which goes to our fan start winding. If we look at our capacitor, this one is going to be marked fan. This one will be marked herm when it's marked fan. That's actually our fan start winding when it's marked herm, that's our compressor start winding, and then this is a jumper that goes to the run.

Side of the contactor feeds the sea side of the capacitor and then coming out of this. The way this is set up is our run, for our condenser fan is coming off of that same c terminal, which is sometimes what you'll see. We could just as easily take this orange wire and connect it here if we had a spade there, because these electrically are the same point because of this jumper. That goes in between c and the run side of our contactor.

Once again, here it says lac. We can see that this is a single pole, single, throw open on fall pressure switch. This symbol means a pressure switch. If this pressure drops, then it's going to open the circuit and let's look at what it's going to open the circuit to.

We can see it's going to break the circuit to our common on our outdoor fan motor. If we look over on this side, let's see if we can find that when this optional device is here, we actually wire through it, and so that breaks this circuit, causing the condenser fan to go off when your pressure drops. So for those of you who are familiar with it, this is a type of a fan, cycling control, but you can see over here that it's optional and that's why we don't have it in the system that we're working on so to strip away. So many of the optional things really, what we have is a low voltage y wire low voltage brown common connecting to our compressor contactor coil.

We don't have this. We don't have this this this this none of this. We don't have this. What we have is compressor, contactor, two different sides, common start and run on our compressor.

Our three terminals on our capacitor, our three terminals on our outdoor fan motor, it's about as simple as it gets, and those are just connected. According to these two schematics or diagrams they're, both correct, but they show different levels of detail and they're really designed for different things. The ladder diagram or ladder schematic making it very easy to trace a circuit in the pictorial or point to point, making it easier to locate components. So that's a really basic look at a very simple system that you'll actually find in the field, and hopefully that makes you more comfortable in reading diagrams, always refer to your legend and your notes.

In order to find out more about the unit, you're always going to learn something as you go through and read all of the all of your notes and pay attention to the details of wire, colors, wiring information and your different component codes. Thanks for watching our video. If you enjoyed it and got something out of it, if you wouldn't mind hitting the thumbs up button to like the video subscribe to the channel and click, the notifications bell to be notified when new videos come out, hvac school is far more than a youtube channel. You can find out more by going to, which is our website and hub for all of our content, including tech tips, videos, podcasts and so much more.

You can also subscribe to the podcast on any podcast app of your choosing. You can also join our facebook group if you want to weigh in on the conversation yourself thanks again for watching you.

22 thoughts on “Wiring diagram tracing – older rheem condenser”
  1. Avataaar/Circle Created with python_avatars Jose Guerrero says:

    Great explanation thanks for the vídeo sr

  2. Avataaar/Circle Created with python_avatars Jose Guerrero says:

    Wow great explanation for the ac thanks sr.👍

  3. Avataaar/Circle Created with python_avatars Brian Mcdermott says:

    Great teaching. Thanks Bryan. Service area Ottawa??

  4. Avataaar/Circle Created with python_avatars Don Johnson says:

    Real question is, where are you guys finding the correct diagrams online? I try a few times per month when working on older stuff and I rarely find anything. I can always find carrier stuff thru the app, but I don’t have that kinda access with any other brands not affiliated with our company.

  5. Avataaar/Circle Created with python_avatars Angel Hinojosa says:

    Thank you so much for these great videos! I’m learning a lot more on YouTube vs trade school

  6. Avataaar/Circle Created with python_avatars bug Den says:

    hey this is my unit NOW in july 8th 2021,,i keep it running as much as i can i am old man money is tight , i still have a full jug of R22 and about 1/2 of another ,,,,,,i was wondering if it would be worthed to ? when the time comes buy a 410 unit change out the txv to a r22 and go that way ? or just sell my UN opened r22 that is sealed still and go with the 410 ? of course in central florida HEAT PUMP is needed couple more wires ,,,,,thank you for all your teachings its all good and it never hurts to review things especially when you cant work anymore god bless teachers .

  7. Avataaar/Circle Created with python_avatars bug Den says:

    how do you explain a COMMON wire ? i was told back in school that its a wire by itself ,,,,do you have the same determination as that ? thanks Service area Orleans??

  8. Avataaar/Circle Created with python_avatars Donnie Robertson says:

    Great job and video like always

  9. Avataaar/Circle Created with python_avatars Tomorrowsyoutube says:

    I like this!!! Exploring older units revitalized this channel for me Are you in Kanata ?

  10. Avataaar/Circle Created with python_avatars Hood Handyman says:

    I was eating this video up till that loud truck pulled in . Great video none the less . This was good. Clear to understand.

  11. Avataaar/Circle Created with python_avatars John Kiss says:

    Thanks for the great video. I really appreciate your content. I mainly work on reach in refrigeration but several of the HVAC info is applicable in my trade also. You said the start components were optional and not present in the system you were using today. Does that mean the start winding is always energized when the system is running? I always thought there had to be some sort of relay to open the start circuit. I see mostly current relays with an occasional potential relay on larger equipment.

  12. Avataaar/Circle Created with python_avatars Eassyheat/ Cooling says:


  13. Avataaar/Circle Created with python_avatars Michael Costello says:

    I love these wiring diagrams explained. Thanks

  14. Avataaar/Circle Created with python_avatars Michael Costello says:

    Why is it L1 and L3. Why not just L1 and L2 etc

  15. Avataaar/Circle Created with python_avatars turner bailey says:

    Thank you sir

  16. Avataaar/Circle Created with python_avatars ClickyMcbuttons says:

    Jandy was here.

  17. Avataaar/Circle Created with python_avatars AG says:

    LIKE BEFORE YOU WATCH people no questions asked. 👍

  18. Avataaar/Circle Created with python_avatars Sami Habib says:

    Hi Bryan , can you please make a video about Stay Brite 8 soft solder that is used on AC lines and their benefits or not compared to classical brazing. Can it also be used for refrigeration units

  19. Avataaar/Circle Created with python_avatars Will Benson says:

    Uhm, to reiterate, pull the disconnect BEFORE you jab in and pry away with a flat head.

  20. Avataaar/Circle Created with python_avatars Jericosha says:

    These videos may seem silly to a lot of us techs, but when starting out this stuff is a God send. Good stuff Bryan.

  21. Avataaar/Circle Created with python_avatars 청소전문가 says:

    Thanks for sharing your know-how

  22. Avataaar/Circle Created with python_avatars Russ M says:

    will you be having your training seminar next march in Florida?
    Russ Mitchell

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