Hey thanks for watching this is the next in our series of using the quick cheat whatever you want to call it cheat sheet, quick, cheat whatever you can find it by going to HVAC our school.com, don't forget the are in their HVAC. Our school comm forward. Slash quick dash sheet, that's forward slash, quick dash sheet and you can find this chart that we're looking at again quick disclaimer. This is a overview, there's a lot of different ways that you could write this chart honestly for different pieces of equipment, but this is sort of general conditions, general operation, mostly for single stage equipment, but it gives you an idea of the relationships between these key factors.

Another two articles that I recommend you read if you're unfamiliar with some of the terms that I use first, I would go to HVAC our school comm 4/5 pillars and slash terms. The terms article talks about some of the terms that maybe are used in different segments of the industry, such as refrigeration or air conditioning. It really depends on what segment of the industry you're in or even geography, what terms are most popular and then the five pillars are the five most common measurements that I suggest that technicians be familiar with you're, not always gon na take them on every single piece Of equipment, depending on the type of equipment that it is ductless systems as an example, but that is suction pressure, head pressure, superheat, sub cooling and delta T. Those are the five pillars and I want you to be really comfortable doing those first before we go on to some of the others like static pressure or compression ratio or discharge temperature.

Things like that that are also very useful, but are not included in this chart. Now one that is included in this chart is compressor. Amperage compressor amperage is a tough one, because we know when it's too high based on the data plate, but that's when it's a lot too high, and so even knowing what the exact compressor amperage should be at a given condition. You can use something like the Copeland mobile app, which is a great app to have for Copeland compressors.

But if it's not a Copeland compressor you'll have to look at at the different manufacturers. Some of them have apps. Some of them have literature, and sometimes you can put in the measurements like in Copeland mobile, and you can check a compressor that way or you can see what the amperage should be under a given set of conditions which can be helpful on that amperage part. But anyway, let's jump in today's which is over charged, so overcharge is one of the most common mistakes made by newer technicians, and it often happens because they are only looking at one thing, as their primary charging indicator remember, charging an air-conditioner is not like putting air Into a tire or filling up oil in an engine, there's not just one factor that you look at.

You have to look at multiple factors, so the case of overcharge we're going to do the same thing. We did last time where we have two different versions. We have fixed metering device with a clear overcharge and then we have a TXV system with a slight overcharge and again I do this where it's slightly on the TXV and it's kind of full-bore up top and again some of you don't say well how much is Too much it's one of those, you know when you see it sort of situations, because it really depends on the piece of equipment, but we're just kind of giving you some things that you might see out in the field so that you can catch it. When you see it and you will notice the white stars, the white stars are our key indicators.

So, let's start up top at fixed metering device. That would be a piston or capillary tube type system. Again, we're talking about air conditioning here so more often you're going to see Pistons as being the most common type of fixed orifice, but there are some others out there and our two primary indicators are our superheat and our sub cooling. Those are our two primary indicators that tell us when we have an overcharge now, some of you may say well what about suction and head pressure, and that is true.

You can use some common rules of thumb to know what your suction and head pressure should be. Suction pressure is generally pretty easy and air conditioning. In most cases, your suction pressure is going to be about thirty five degrees lower than your endure return. Air temperature.

When I say suction pressure, I specifically mean your evaporator temperature or your suction saturation. We talked about that and the last one we talked about an undercharge system for charging a system you may want to kind of brush up on that, but very basically, every time we are looking at a gage pressure that equates to a saturation temperature, which means the Temperature, the refrigerant will be when it's in a mixed state, so in the vapor and liquid are present at the same place. At the same time, that's what we call saturation and so when it's at saturation, that's the temperature will be in the case of the evaporator coil. That saturation is what we call evaporating temperature or evaporator temperature boiling temperature really honestly inside that evaporator coil.

And so, if your temperature inside is 75 degrees, that's going to equate to a 40 degree, evaporator temperature and so on a fixed metering device system. We can see well if our pressures are higher than that. So let's say that my saturation pressure is representing a 45 or a 50 degree, evaporator temperature, even when it's 75 degrees inside we would say our suction pressure is high. Also, head pressure same sort of thing: you can calculate your CTO, a your CTO, a target which is condensing temperature / ambient.

That's a long one will said again, condensing temperature / ambient, and what that is is that is your condensing temperature, which is sort of the other side of the system. It's also a saturation temperature, but it's the temperature that the refrigerant will be when it's changing state from a vapor to a liquid. So when you have that mixed state inside your condenser inside your condenser, you've got three different things going on D, superheating, condensing and sub cooling. But while it's in that condensing zone that condensing temperature is going to be somewhere between 15 and 30 degrees.

Above your outdoor ambient, that's that condensing temperature / ambient now that changes depending on the seer rating and again really it has more to do with the size of your condenser. So a larger condenser is gon na have a lower CTO, a a smaller condenser physical size, physical surface area is going to have a higher CTO a so older pieces of equipment tended to run that you know we used to say 30 degrees over ambient. That's what I learned in school 30 degrees over a me and that's how you charge it that was kind of an old-school way of knowing what your head pressure should be. Nowadays, we see more in that 15 range being more common with larger condenser coils, but regardless, if you see a condensing temperature, that's higher than that based on the type of equipment you're working on, then that's an indicator, one indicator of overcharge.

But those are the more simple ones. Those are the more basic ones again and when we start to talk more about what your targets are, you either have to look at something like the five pillars, article which goes through all of the targets, but again using measure quick, helps you define what those targets Are meaning what zone you should hit, and so, whenever you're looking at measure click those green zones show where you're supposed to hit so long as you put the right data in again, it's like anything, that's garbage in garbage out. You have to put the right indoor return temperature. You have to put the right outdoor temperature in there and the right information on the type of system, and then it will tell you what your targets are.

But again, indicators are of overcharged, massive overcharge with a fixed metering device. You're gon na have high pressure. You're gon na have high head pressure. Your super heat is going to be low, and super heat is an indication of how far we're feeding boiling refrigerant through the evaporator coil.

We've talked about this many times, but superheat indicates to us that all of the refrigerant has been boiled off fully change state. Whenever we have a positive number, whenever that suction line temperature coming out of the evaporator coil is higher than the evaporating temperature means that refrigerants completely boiled off when that number is low, it means that boiling refrigerant has traveled very far through the evaporator coil, and when That number is high. It means that boiling refrigerant stopped boiling very early in the evaporator coil. So when you think of superheat, think of it almost like a fill value when superheat is low, that means that the evaporator coil is filled far when the superheat is high.

That means that the evaporator coil is not filled so far and when you're thinking about overcharged, specifically with a fixed metering device system - and this is a key indicator for fixed metering device, low superheat - is a good indicator of overcharge when you also have these other factors. Like high suction pressure, high head pressure and high sub cooling, those are really good indicators. I could just have easily had put white stars by you know the first four here, because they're all of these, in fact, errs, are actually quite important with defining overcharge. But when you hook up to that piece of equipment - and you check your superheat and you see it to be very low or heaven forbid, even zero, which means you have liquid still in the suction line.

Coming down towards that compressor, you see that you have a high sub cooled number, which is again that sub cooled number when it's higher. It means that you're stacking more refrigerant in that condenser when it's lower, it means you're stacking, less refrigerant in the condenser. Again, when I say stacking and they're in the condenser, remember the condenser feeds into the liquid line that then goes to that metering device. So as we back more refrigerant up, we stack more in it and it allows it to cool more and that's what sub cooling really is again we're talking about the relationship between your condensing temperature and the actual liquid line temperature measured with a temperature clamp.

That's what sub cooling is then, with overcharge. You are going to tend to see higher compressor amps on a fixed metering device system, and that's because not only are is a compressor working against higher head pressure, but you also have greater load because you have more dense. Vapor coming in to the inlet of the compressor, because again that compressor is pumping vapor, it's moving. The and some people say: well, it's not a pump technically, it is.

If you get into the definitions of what a pump is generally, when we say pump, we mean something that pumps liquids. A compressor is a compressor because it's it's literally compressing because it's moving a vapor, but it's still moving it and when we have higher suction pressure. There's more of it that it's moving and when we have our head pressure, it's moving it against a greater back pressure, and so that compressor is going to draw higher amperage. It is a pretty good indication of overcharge you're gon na pretty consistently see high compressor amps when you have overcharged now.

Does that mean that it's going to over amp based on the rated load amps of that compressor? Well, the answer is often no because again those rated load amps have a pretty good buffer built into them. So you may not be over amping on from that standpoint, but from the basis of how it would normally operate. So if you took a benchmark of that equipment when it was charged properly and then you've checked it later, you would see that they compress your amps go up you're, also going to see with, depending on how extremely overcharged it is again on a fixed metering device System you're going to see that you have normal to low delta T and that's because, as you keep packing refrigerant into that of a protocol, eventually you're going to start raising that evaporator temperature and when you raise the evaporator temperature. Well, what happens you remove less heat from the air flowing over the evaporator coil, so you can overcharge a fix metering device system to the extent that you actually see decreased capacity on that system, slight overcharge in some cases, you'll actually see your delta T increase a Little bit, but then you've run the risk of still having that low superheat, which can damage the compressor, maintaining super heat entering the compressor.

So that way, you have that target number so that way, you're in the safe zone to ensure you're, not flooding back with liquid refrigerant, that's huge for compressor, operation and again keeping it. So it's not too low, not too high, both of them matter for our compressor. But overcharge is a really big compressor killer, as well as ultimately a capacity killer. Your compressor is going to draw a higher amperage.

So that's going to impact your current draw as well negatively. Now, let's go down to a TXV system, and this is a more slight overcharge, but a lot of these rules also apply if it's pretty pretty heavily overcharged on a TXV system, and the big difference with the TXV system is that the TX v maintains a constant Super heat: that's its job, to maintain a constant superheat. Now my friend Jamie kitchen, at Danfoss, he takes umbrage of that and says at exp, doesn't really maintain a constant superheat. It does have some variation in the superheat, and that is true.

If you have higher pressure, differential or lower pressure differential, you are gon na see some float and the superheat that even that TXV maintains, but it's maintaining a much more constant superheat than a fixed metering device. Would that is what the TX V does and THD does it very simply? It has a bulb on the suction line. It has an external equalizer that takes the pressure on the suction line, so it's basically measuring superheat. Some people think the external equalizer has something to do with equalizing in the off cycle, and it doesn't it to some degree.

Of course everything has something to do with everything, but purpose of the external equalizer is to equalize. The valve is to be a balance of forces against that bulb pressure, the bulb pressure being the opening force of the bow and the external equalizer being a closing force on the valve. So if the bulb gets warmer, the valve opens in order to maintain superheat and if the pressure at the outlet of the evaporator coil goes higher, then that balances that force and forces it closed. So it's a balance between the pressure at the outlet of that evaporator coil and the suction line and the temperature of that suction line.

That's impacting the pressure inside of that bulb. It's a concept, that's harder for new technicians to get what it really means is you can overcharge athe system by a lot and you're, not gon na see your suction pressure come up at least not significantly and you're. Not gon na see your superheat change much at least not significantly, and so what happens to a lot of people is they'll start adding charge because they're looking at that suction pressure indicator because they say I've been told. I need to get to this pressure.

Maybe it's a 40 degree of a protocol, or maybe somebody told them on an hour 22 system. You need to get to 75 psi suction or whatever, and they just keep adding refrigerant and the head pressure starts going up, but that suction pressure doesn't go up and the superheat doesn't change. So it may change a little bit when they're, adding the refrigerant, especially if they're dumping it in liquid and so they'll see it they'll, see it change and then they'll see it go right back where it was before and that's why, when you're charging a TXV system, Your number one indicator is sub cooling, sub cooling is your indicator and on ITX V system, they're generally gon na print it right outside on that condenser label. Now you will notice that when you overcharge a lot or even slightly, you will start to see your compressor amperage come up and that's just because you're increasing the back pressure that the compressor needs to work against suction pressure.

Staying pretty much the same suction superheat. Staying pretty much the same so long as the valve expansion valve is working properly, but it will increase your compressor amp, so you are hurting the efficiency of that piece of equipment. Another thing you're gon na notice, is on a txt system, even with overcharge your Delta T's gon na stay, pretty consistent and so at exp actually does a pretty good job of protecting the compressor against an overcharge by throttling down. As that super heat starts to drop that TXV throttles down, and it prevents that superheat from diving on you preventing that flood back.

So let's look at the measure quick, app and see what symptoms it's gon na show, because it has a really nice built in diagnosis. Example of an overcharge system. So again, if you want to load in some test, data just hit the gear at the top right scroll down and then select one of these sets of tests of demo data here, we're gon na go to an AC, overcharge, TXV system. So we click that, and now you're gon na see right off the bat that up here on the top.

We are way over our target on our head pressure, so our head pressure is definitely high, but you'll notice that our suction pressure is still in the target zone and that's just what we talked about. Let's see our super heat is in the Green Zone, a little on a little low on the Green Zone, but still in the acceptable range, but our sub cooling is really high. Generally speaking, for most typical equipment that we work on at 10, degrees of subcooling is sort of the general sub cooling target. But again, look at the manufacturer specifications to know what it should be, but it doesn't take a rocket scientist to know that 23 is high and so the combination - I really don't have to look any further on this.

I can see that most everything is in its target zone here. Other than sub cooling is high. Head pressure is high. I know that I've got an overcharge system, so I'm gon na go ahead and pull out my recovery tank, I'm going to hook my Center hose up to or use a probe and hook it up from the liquid line to my recovery tank and I'm gon na Slowly, bleed some liquid refrigerant off into my recovery tank with a scale under the tank very important until that sub cooling starts to come down, and do it a little bit at a time few ounces at a time until you get it to that proper zone, let It run let it stabilize and then, when it's all said and done, we will clear these flags up in the top right of measure quick.

You can see here. It's got three factors that the system may be overcharged. To that say, it may be a dirty condenser and again there are some things here that seem like a dirty condenser, like maybe the high head pressure here, you may even in some cases, get a higher sub cooling, but you're not gon na typically get sub cooling. This high with just a dirty condenser, this is going to be lower in in the correct zone or maybe even a little low in some cases, and our head pressure is gon na be our indicator.

If it were dirty condenser coil, we don't want to jump to conclusions. We don't want to charge based on suction pressure. We don't want to charge based on head pressure. We have to look at all of these factors and again there's six on screen.

Here we get added more, we could add in discharge temperature, we could add in static pressure, there's a lot of other things that you also want to know how to do is not a comprehensive list, but we try to put enough on here that a newer technician Is going to be able to say okay, I can tell based on the measurements that I'm taking high suction pressure high head pressure, low superheat, high sub cool high compressor, amps normal to low delta T the community device system. I've got myself an overcharge don t, -- xv system even easier. I've got high sub cool and I've got high head pressure. Let's go ahead and get this where it should be now, along with that, because if you're looking at measure quick, you see that red flag, it says: we've got some indication, it may be a dirty condenser go ahead and either wash the condenser or at least visually Inspect it because that's an easy thing to do right: this is where real-life diagnosis can really help.

If you got a condenser that looks dirty we'll go ahead and do that first before you start pulling refrigerant out, because that could potentially impact some of your measurements anyway. And it's easy enough to do so. Go to the customer and say it looks like we're overcharged with refrigerant, but step one would be to wash the condenser coil. Here's the quote for that and then here's the quote to recover some refrigerant properly.

Let the customer decide from there, but that would be sort of a a progression I would take. If that condenser shows any signs of being dirty and a lot of times they do again. That shows you the value of metric quick, because it not only gives you what is really the problem, which is going to generally be the top one, but also some other things to look at, because in real life we often do have more than one thing wrong. We have the main thing, but then we also often have some other things that could be going on with the system, but what I don't want you to do is jump to replacing expansion valves and adding more refrigerant.

Those are the two things that I see. New technicians do most often because they're primarily looking at suction pressure or maybe superheat, but you have to know what type of equipment you're working on does it have a TX v doesn't have a fixed metering device and also make sure you know what your target zones Are depending on your indoor and outdoor conditions and again you can follow up on that by reading the five pillars or you can start using measure quick and, as you go through measure quick, it has targets built within that software now sit. Those are the symptoms of overcharge the next one that we're going to do is low end or airflow or low return. Air temperature, so low, evaporator load, we'll see you on the next one.