Good morning, everybody again we're going to talk about pump down and recovery and specifically focusing on how to use the new calculator on the app, because this comes up a lot. Whenever folks are about to do recovery, they always forget how much refrigerant you can put in a tank, and then it causes you to just sort of do the old uh. I think i can fit a little more in there and that's not really the right way to do that so um. To start with, i wanted to talk a little bit about pump down, because pump down is something that we used to do all the time that now we can't do all the time.

So, let's start there does anybody know the two circumstances that you can no longer do pump down effectively for the two reasons why pump down is difficult? Now: ronnie, okay, it's difficult when the compressor's not working. So that's always been true max micro channel condensers and scroll compressors, those that is the correct answer. We got ourselves a regular ken jennings up in here, literally literally ken jennings, max same person, hey, hey, bert, how you doing! How are you i'm really good? I'm glad you could make it. I was on time, okay, um, so microchannel condensers.

You don't want to pump down because you can explode them. They are not designed to hold the entire refrigerant charge, whereas traditionally, traditionally a condenser is designed to be a maximum of 80 percent full, even when it has its entire system charge. So a brand new condenser, that's not micro channel. You pull it out of the box that condenser coil is only going to be 80 full now.

One of the challenges that we also face is scroll compressors. Now it's not so much that it's a problem to pump down scroll compressors. It is a problem to pump them down into a vacuum which has always been this uh. This tv is really this tv's going to start playing a preview.

That's good! Thank you. Thank you, tv! Very instructive. Yeah! That's that's! Nice! That's! That's! Really! That's really! Nice! I um, if there's a way to keep this from going off. Probably not.

I just have to touch it every once in a while there you go i'll, just touch it every once in a while um. So it isn't so much that the issue is pumping down a scroll compressor in the sense that um it's it's not something you should avoid doing, but you just have to recognize that once you pump them down to a certain point, they're going to stop pumping down They're likely going to go into some form of bypass and then you're going to lose some of your progress and that's the problem. So does anybody have because i don't have a rule of thumb for this? Does anybody have a rule of thumb of how deep to pump down a modern scroll compressor before they start going out on bypass? If we read the copeland bulletins, it would probably tell us, but you know reading, am i right anyone no 10 psi. 20 psi.

Josh is has heard 10 psi, probably from me, because i was probably making it up, because i always tell people not to go below 10 psi. But i don't really know why why i made that okay. So here's the thing to be careful of when we say don't go below 10 psi. What we're not saying is that it's okay to vent.

What's left, that's right! Absolutely! That's not what we're saying we're just saying that you can't pump down lower than that. So that means that in some cases, you're going to have to pull a recovery tank off of your truck afterwards, when you're done with that. So if you're going to do that anyway, then it doesn't necessarily matter if you pump it down to 20 psi or 30 psi or 10 psi or whatever the case may be right. We are wanting to prevent that scroll compressor from hitting its safety, where it uh, where it's going to go in a bypass and start to equalize right.

So that's what we're trying to prevent! I don't really care what rule of thumb you come up with now. Let's think of some common examples here, let's say you're going to replace an evaporator coil. That would be a really common case where you would pump down a system or you're going to swap out a line dryer, something like that and it's a scroll compressor or it's a micro channel. I would suggest going ahead and pumping it down, but not worrying about pumping it down nearly so far 50 even 60 psi and then go ahead and finish it off with your recovery, tank and machine.

Now, when you do that recognize that um, i forgot what i was going to say: well, okay, this is what i was going to say that required an edit. No, whether this is going to require an edit here. No, it's that when you're down to that point, where you're in the vapor only phase the vapor only phase is a tiny amount of the overall refrigerant. As soon as you get into vapor only phase, it's not going to make up a significant portion of your system's charge.

That's what i was that's what i was planning on saying before my mind went blank. I was just looking at your face and it was so blank that the blankness just rubbed off on me so um. So, while we're editing, i've never had a skull compressor going to bypass unless something was wrong with the compressor. What's this you're talking about or if it doesn't have an accumulator, if it doesn't have a cumulative pressure, is so high? No, no! No! No! No! No! No! No! No! No! No! No, if you pump a scroll compressor down, says, maybe because you're always only pumping it under 10 psi.

But if you pump a scroll compressor down many of them, and this isn't true of all of them. If you pump a scroll compressor down approaching atmospheric approaching atmospheric um eventually, i know it's. Okay, though it's fine, okay, jesse says that most times, they'll pump down all the way i mean i've had it happen. I've had it happen to me on several occasions or the high pressure is so extreme.

Why does it being a heat pump matter? Why does that matter? Yeah, but okay, so i guess i can see what you're saying is that potentially you could have a lower pressure at the well, but it's not a matter okay. So the reason why it does that the reason why the scroll compressors do that, where they stop pumping at some point, is because they have a no that's, not why it's, because they have a point where it creates a separation in the scroll plates. When the compression ratio gets too high, so it's a compression ratio thing, it's not a head pressure thing i mean there is there can be a head pressure thing too uh like a head pressure, venting um, where it vents back into the uh. There's a word that i'm looking for here, that's not coming to me it's the morning: okay um, but anyway bypass sure a valve.

It's a valve right, a relief, a relief, that's what i'm looking for a pressure relief that goes back into the compressor crankcase, but but there's also a a safety nowadays that they're putting in a lot of the scrolls that prevents your compression ratio from getting too high. So, as your suction pressure drops, your compression ratio continues to go up and at some point it can go into bypass the point being that if you can pump it down pump it down, don't pump any compressor into a vacuum. That's not a good practice so pump. It down to one psi, two psi whatever you know just just right above atmospheric, make sense great.

So don't try to do that on micro channel. If you're working on a scroll then just keep in mind that that can happen. If you pump it all the way down now i wanted to talk about recovery tanks because we're going to be doing more recovery than we ever have before. Because of these reasons that we've talked about in the past heck in the past.

You know there was a time where we would just you know, pump down the the unit before we would change it and just send it back and you know make the scrappers deal with it. You know that was that was the super old-school way. Well, that's not how we do it anymore, so we're doing a lot more recovery and it's really important that we don't overfill tanks and that we understand tank fill okay. We've talked about this a lot, but i want to make it really simple: it's why we've built this new tool.

So if you update the hvac school app and you scroll down to the bottom, we have a recovery tank, fill calculator. There's a couple things on here: it doesn't have every single refrigerant in the world. We just pick some of the most common ones, so we're gon na go and select r410a, and then it has a maximum temperature. Now, the reason why that even has that there is because the tank itself is rated at 77 degrees fahrenheit.

So when it says wc, which is water capacity, which we're going to talk about in a second it's rating, it at 77 degrees. And so, if you follow the ahri guidelines, it's called hri schedule k. They talk about everything being based on 77 degrees, 410a, r22, water everything's, based on 77 degrees. The problem is, is that that's not a realistic temperature that you can potentially see in the back of a van, so a lot of us use 130 degrees as sort of a reasonable maximum, and that comes from sort of the the reasonable maximum that you see from The manufacturers of the refrigerants they uh, i forget the exact term that they use, but that's that's where that 130 degrees comes from, it's sort of like worst case scenario, and so that's what i would generally suggest that you use.

So all you have to do pick your refrigerant leave your max temperature, where it is and then you enter two things and i just want to be clear where you find these so right here it says: tw 26.1, so tw is tear weight 26.1 and then you Have water capacity which is wc? So, let's see here, water capacity is 47.7, 47.7. Okay, so our total tank weight maximum is 59.54. Our total internal weight, the amount we can put into this tank maximum is 33.44 pounds of r410a that takes into account the 80 maximum and it takes into account the density of r410a at 130 degrees. It's math.

That would be hard for you to do, because what a lot of folks will do is they'll say well. I just take the wc and i multiply that times. Point eight and that gives me eighty percent fill well. Yes, that's eighty percent fill if you were putting water in it and i certainly hope you were not - and you said full weight - told away, meaning you're weighing your refrigerant and the tank right.

So when i say total weight that is, tear weight plus fill weight, which is what it says right there. So tw is tear weight. That's the empty weight of the tank. Wc is water capacity, how much water to fill the entire tank, but we don't want to fill the entire tank.

We want to fill it 80 percent, so it's 80 full even at 130 degrees. Fahrenheit, i'm sorry, six pounds! Where are you getting six pounds from seven pounds? What is he, what is he looking at? Does anybody know, i think, he's trying to do the difference between the oh you're trying to take a difference? No, this is how much refrigerant you can put in that's how much refrigerant you can put in 33.44 pounds of 410a. The top is what the total thing's gon na weigh when it's all said and done from over here rob grant's rubbing off of them, the gray. The color is hard to read.

Yes, it is, it is hard to read yeah yeah yeah it is it is. It is actually kind of well it's not. It's actually not hard to read on the phone but uh, but it's a little. It's a little washed out right here now, so let's go back so this is.

This is important if our trainer can't figure this out. We need to make sure that i that i made this in simple enough terms. So maybe we should add tw here right. So you enter that that's the weight of the tank empty and you get it off the rim and it's also confusing because when it says tank water, it's also tw, okay, that is true.

That is true, but on your tank it says wc right, so you should do water capacity, parentheses, wc, uh, yeah yeah, but i think either way. You're gon na have to get it. It's not tar weight. That's another thing, bert likes to say all the time on videos that he makes about it.

It's not there's no tar in this tank. No, it's not water column either. That's the other thing, it's water capacity. So when we enter this water capacity, 47.7 pounds is how much water we would have to put in to fill the tank 100.

Okay. That makes sense. So if we wanted to figure out 80 of its water capacity, we would take this and multiply that times 0.8, but the problem is we're not filling it with water, which is the whole reason why we need this chart if we were filling it with water, we Wouldn't need this chart now we still might need the chart because again, the tank water capacity is based of water density, liquid water density at 77 degrees, and i want it at 130 degrees, so it kind of makes it confusing. So there's a lot of math.

That's going on in behind this in order to give you this result, but the point is: is that when you um, in fact, you know if we wanted to get real crazy, you could write the r410a. These numbers right on the tank because it would always remain the same if it was r410a. If it's a different refrigerant, then you'll get a different result. So if we change this to r22 now you can put more in it.

Yeah significant because r22 is more like water in terms of its liquid density more similar to water anyway, any questions about that pretty simple: okay, nowhere on the tank! Nowhere on this tank. Does it tell you what this tank will weigh when it's completely full? That's the point nowhere on here. Neither of these numbers include that one tells you how much stuff can go in the tank if that stuff is water and if it's 77 degrees 100 full, which we also don't want. The other number tells you how much the tank weighs when it's empty.

So it's easy to know how much you got in the tank. Look at the tear weight. Look at how much the tank weighs whatever the difference is. That's how much you got in the tank.

That's really simple, but what's difficult is to know how much can we put in the tank make sense cool. So we've talked about this uh quite a lot lately, but i always want you using a scale when you're recovering and when you're charging and in terms of anytime you're making a major repair. I want you to weigh out the refrigerant charge in your tank, and so that means even things like if you're going to use an ice bucket, which we do a lot, especially with the smaller tanks, in order to try to keep the tank cool. Obviously, you can't weigh the ice bucket and the tank at the same time, so you have to make sure you're not going to overfill the tank while you're doing that, which means you're going to have to pull it out of the ice bucket periodically and re-weigh it.

Just to see where you stand, and that's also where this comes in handy, because that way, if you forget, like oh shoot, i forgot what i wrote down or i forgot where you stand, you can always tell how much is in the tank. All you had to remember now is what it weighed before you started, so if anything write that down somewhere any questions about that quick tour of the other things, because some of you may not know about this app, there's a couple tools here. That will be handy to you. Some of them are pretty nerdy, but the under load capacitor test - if you ever want to do that, we've made that a lot easier to use and it even shows yeah.

It shows where you connect um, but all you have to do is measure your voltage across the capacitor, the amperage of the motor start winding, which would be you know in a lot of cases, going to be your blue wire coming off your herm terminal. If it's a carrier, of course that varies and then the capacitor rated microfarad, but another thing that we did to make it a little less likely that folks are going to mess this up. So we added a message that warns you that if it's out of specification too high, that's not a sign that the capacitor is bad. That's a sign of a mismeasurement of some sort, so we're looking for capacitors, don't fail too strong.

They don't fail too high of a rating that doesn't happen and whenever i say this, people like to point out these super weird exotic things that could happen in reality in the field. That does not happen if you're measuring a capacitor that is reading a higher microfarad value than what's printed on the capacitor. It means that your measurement is wrong, and i so that's what i don't. I don't want folks, because before this this calculator, if you would miss measure in some way, it would tell you.

Oh it's it's out of range, you need to replace it, so we change that now. It only tells you to replace it if the measurement is too low. So if you look here at the at the measurements, it tells you that i have a 20 i'm i have a 20 microfarad capacitor, but my calculated microfarads are 57.36 and then superheat and delta t can come in handy, sometimes as well specifically when you're working on A piston system trying to find what your super heat should be now keep in mind that whenever you're using a superheat calculator, you have to get your return. Air wet bulb temperature, which means you're going to have to have a psychrometer in your return air.

You can't do it if you don't have that, because it can vary wildly in terms of superheat, especially in our market. Relative humidities and the returns can change a lot and it will change your superheat a lot. So you just enter those numbers and it'll give you a reading um. No, you cannot so uh at some point.

We may do that. It just makes the math a little bit more complicated. I haven't done that yet so yeah um again we're not going to use that we're not going to use that that much it's a high demand thing voltage imbalance for anybody who ever works on three phase. This is actually really handy if you're ever a normal test.

In three phase should be to check your voltage across all three legs on the load side of your contactor, to make sure that you don't have undo voltage imbalance, and this will tell you what your imbalance is where it's, where it lands, because, if you're over one Percent it says you should try to decrease the imbalance to get to one percent. It shows you what your motor temperature increases, as well as what your average voltage is based on your entry. So again, you're not going to do that not going to do that too often, nitrogen pressure. Oh, this is one that i get a question about a lot just because it's not something we do a lot.

But let's say that you are pressurizing a unit when it's cold and then it warms up so say: you're working on a ductless system or something and you get the thing pressurized up and you leave it and you're doing something else. For a couple hours and the temperature goes up by 10 degrees after you pressurized it. So if my pressure actually will do the opposite, we'll say you you pressurize it in the afternoon, then it gets cold in the evening. That would be more likely.

So let's say you put 350 psi in and the temperature, when you added it, was 85 degrees and then the temperature after you cool down to 70 degrees. This is going to show you what your adjusted pressure will be so before it was 350. After that temperature drop it's going to be 339., there's no leak, that's normal! That's what's supposed to happen right, and so the point is that temperature variation makes a big difference now. Part of the problem with this is is that it doesn't just matter what the outside temperature is.

So it matters the temperature of the lines running through the attic. It matters the temperature of the coil, so that all kind of averages out. So it's not quite that clear, but it does give you at least an indication that my pressure dropped. Well could have that.

Could that be because there was a significant temperature drop or maybe my temperature went up and my pressure held or my pressure even went up a little bit, but maybe i still have a leak right. So it's just something to be aware of. You have yeah okay, yep, i was leaking. My pressure was going up, yeah cool, any questions about any of that again main message today is understanding tank fill recognizing that you can't always pump down and what to do when that's the case, and how much does this app cost? This app is for you today.

It is free with purchase with purchase of sponsors products there's actually not even any ads on it. Wow wow, that's a good deal. We do we do that's what i've been thinking. We need some ads all right, thanks guys, 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.

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