All right, this video is going to be about compressors, and actually you can see back behind me here. We've got a diagram of a scroll compressor, one of the original original patent drawings of a scroll compressor, there's a lot of different types of compressors in air conditioning refrigeration systems and just a couple of them that you'll see if reciprocating is traditionally one of the most Common rotary compressors are for generally smaller units. Scroll compressors are more and more common nowadays, in both refrigeration and in air conditioning, and then you also have some larger compressors known as screw compressors and some trophical compressors and you're typically going to see those in very large applications. Those are the typical five types, but they all work in similar ways and their job is to compress the compressors job is to compress imagine that vapor, refrigerant and vapor means it is not in the liquid state.

Isn't it is in the vapor state. So this fully vapor all of these compressors are designed to compress complete vapor. All compressors decrease the volume that the refrigerant is in in order to increase the pressure. That's what it does.

It decreases the volume, the space that the refrigerant is in inside that compressor, which then increases the pressure and causes it to move, because we know high pressure goes to low pressure. That's one of my basic rules, and so the compressor creates that difference. Now, where does the compressor get the energy from well most compressors? Nowadays they have electrical plugs right on them and they're generally, a material called fuse it-it's like a glass plug that you that you make these electrical connections and the electricity is a lot of pass through. The shell, but once it gets inside the shell, the refrigerant and the motor and the compressor are all there on the inside.

That's the most common type. There are compressors that can be accessed through a series of bolts that can be removed and those are called semi-hermetic. Compressors there are compressors that are completely sealed that you're, not they're, not designed to be accessed at all. The only way to get into them would be to cut them open and those are called hermetic compressors and then an older type of compressor.

That's still out there. In certain applications is called an open drive, compressor and in an open drive compressor, rather than introducing energy into the compressor via electricity through a few site plug. Instead, you actually drive a shaft, and so you have the the compressor is a separate opponent from the motor. So you actually connect a separate motor to the compressor.

Those are rare because you have a shaft, that's coming out of the compressor and that is very likely to have leaks on it. And so it's a really common issue with open drive compressors when they were common and so now they've gone to mostly sealed weather, semi-hermetic or hermetic. So, as we mentioned, they all function by pumping vapor. But a really important thing with compressors is that when we are setting up a system that we're only feeding it with vapor, so this is why we test something that we call superheat and it's a term that you hear a lot in air conditioning.

It's one of the reasons why we measure it is so that we can ensure that all of the refrigerant that's entering the compressor is fully vapor, because if we get liquid refrigerant into that compressor, it can cause damage if it gets up to the head. The part that actually does the pumping - so that's very critical. Another really critical thing with compressors is that we get the temperature right, so the temperature of that suction gas - that's coming into the compressor - needs to be the right temperature and at the right mass flow rate. In order to keep that compressor cool, if the compressor is refrigerant cooled, which is by and large the most common, there are two different types of compressors air cooled and refrigerant cooled, but for most of the industry, we're typically using refrigerant cooled compressors, which means that the Refrigerant that enters the compressor is actually what's doing.

The cooling of the compressor and the motor cooling in those internal parts, and so, if the refrigerant coming into the compressor either is too hot. But temperatures too high of the refrigerant or if the mass flow rate of the refrigerant meaning the amount of it that's moving through the compressor, is too low. Then it can't cool the compressor but identified a couple things here. First compressors pump vapors, so we can't bring liquid into the compressor.

Secondly, we have to make sure to control the temperature and the mass flow rate the amount of refrigerant coming down that suction line entering the compressor in order to make sure that it stays cool. There's another thing that we talk about a lot with compressors: it's called compression ratio and compression ratio is just the absolute discharge pressure divided by the absolute suction. Basically, all that means is is how much is it needing to increase the pressure when that compressor has to increase the pressure to a higher degree, there's more waste, because there's more re expansion of the high-pressure gas coming out of it? That's all fancy talk to just say that when a compressor has more work to do, it has to increase that pressure for lower base pressure to a higher pressure. That differential is greater, then that compressor is going to do less work and it is going to run hotter, so higher temperature, and so those are all factors that we have to consider with the compressor you throw that compression ratio factor in there as well.

Oil control is really huge with compressors, because the compressor has oil inside that crankcase and at least in most cases it's going to have that oil. Inside that crank case. There is a compressor that actually use some magnetic bearings out there, which is pretty cool, but most compressors use typical bearings and they need to have oil lubrication, and so a small amount of oil is circulated through the system with the refrigerant. But the bulk of it should be in that compressor, shell, but there's a couple different factors that can that can cause problems with that oil.

One is if we do have liquid refrigerant coming down the suction line into that compressor. It costs foaming and loss of oil loss of viscosity of the oil. Another factor is: if the compressor overheats it can break down the oil. That's another another thing that we look for and another reason why we've got to make sure to control that compressor temperature.

But there's another factor which is what we call flooded starts and that's where liquid refrigerant migrates to that compressor during the off cycle, especially if the compressors in a cold environment, say it's a split system and it's located outside and that liquid refrigerant gathers in the oil And then, when that thing finally turns on it creates that little mini explosion in there and a lot of the oil is lost as that liquid refrigerant begins to boil. So that's another thing that we look for. We do want to make sure that we don't have flooded, starts and compressors and that's where we use things like solenoids and pump down solenoids and compressor crankcase heaters and hard shutoff TXV. Those are all strategies that are used by manufacturers in order to prevent flooded starts, but let's get down into the nitty-gritty of what the compressor does and how it fails.

We talked about how it pumps vapor, but it takes vapor from the suction line down that suction line. It enters the compressor and then it pumps it up and it goes in the discharge line and then from there it goes into the condenser. Let's think of how to think about this, because you'll notice that the suction line coming into the compressor is low-temperature and the discharge line, leaving the compressor is high-temperature. If you touch one and then the other you're going to notice, there's a big difference in temperature, I don't suggest that you go touching a discharge line because you can burn your hand, but there's going to be a big disparity in temperatures there, a typical air-conditioning equipment Running under nor conditions, you usually get to see something like a 50 degree, suction line temperature entering the compressor on that large line and then coming out of the discharge line.

You may something see something like 165 170, it's gon na be pretty typical, and so that means that you have a hundred and twenty degrees of increased temperature inside that compressor. One reason is: is that it's picking up a little heat as it cools the compressor itself and the motor and all those sorts of things. But another factor is and then the reason why we see the majority of that temperature increase is because, when you compress something when you take a mass and you compress it, those molecules bounce together more more fast, more quickly. So higher velocity temperature, by its very nature, is average molecular velocity or average kinetic energy within a substance, and so when you take a something that's in a higher volume and you compress it into a smaller volume.

Imagine it like a bunch of ping-pong balls or a bunch of and all those little super bouncy balls that you used to get from the from the coin. You know operated thing at the at the grocery store and you take all of them and they're bouncing around and you start to force them together. Well, what happens? Will they start to impart energy on each other as they're bouncing against each other and against the sides, and so because temperature, by its very nature, is average molecular velocity when we force things together, we see an increase in temperature now. Does that mean there's an increase in heat? Well, there is because you have the increase of heat inside the compressor from the motor, the motors electrical that has windings and so there's a little increase in heat, but but largely it's that it's not an increase in heat.

It's only an increase in temperature because all the heat that was absorbed was absorbed in that evaporator coil and then maybe a little bit in the suction line when it was coming back. But we still noticed that that suction line is say, 50 degrees. And now we force it together and all of a sudden, the temperature goes sky-high. Well, the temperature goes sky-high without a huge increase in the overall heat content, just by decreasing that volume, thereby increasing the pressure and the density.

Some one increase the pressure and density. Now we start to see an increase in temperature, and then it goes into the condenser, rejects that heat off and that's how we turn it into a liquid. A compressor cannot turn vapor refrigerant directly to a liquid because, as we compress the temperature increases, and so it won't allow it to condense, it has to go through that condenser allow the heat to be rejected before it can actually become a liquid. So a lot a lot of technicians have this false sense that the compressor presses it from a vapor to a liquid and that just isn't possible without having that heat rejection that the condenser provides.

So hopefully that was a good little introduction into compressors. There's a lot of different ways that they fail: we're not going to go into that right now, but we'll do that in a separate video ways that compressors fail on how to diagnose them. This is just an introduction. Hope you enjoyed we'll catch you in the next video.