This episode that the HVAC school podcast is made possible by generous support by testo and carrier. You know, ii saw a bloke. He walks up to you in a bar she's, a little too close and then starts talking to you. You try to ignore.

They doesn't take the hint he starts in about total nonsense. Now you know why he's talking about stuff about enthalpy lines and mallya diagram? Well, that's brian or yes. Yes, yes, how all of it is true. I am brian, and this is the hvac school podcast part of the hvac, our school comm family of products for the service technician community, and today we have our regular contributor, jim Bergman.

I hope he remains a regular contributor and I think he should just so long as I'm able to hang on to that little piece of black mail that I have on him and Jim's going to talk about one of his favorite subjects, which is evacuation. This is going to be just one piece in a large conversation that we're going to continue to have about evacuation. So we don't hit everything, but we hit some of the high points, and this episode is long enough as it is. Another thing that I was able to get my hands on was a recording of Jim speaking to a technician.

Recently, I don't know who you are. I don't know what you want, but I wouldn't find you and by you to death about vacuum, gauges and colourable for tools all right, so we are recording we're going to talk about this time. This time we won't talk about evacuation. I think that's sort of an easy one for you sort of a softball.

I think yeah, that one sucks um you don't like it. No that vacua ssin suck! Oh, we whatever you want to talk about. Let's do evacuation, though, because I think evacuation. First of all, that's if I'm counting correctly, I think it's the most popular video you've ever done.

Is your video on the what was it fifty two seconds to three hundred microns or whatever? It was well. What was five hundred microns yeah, which is a video that I watched just to like put me to sleep at night, because it's a so compelling. I thought it was the wind noise in the video that made it so good. So it was.

The wind noise was good, the music there's, the only criticism that people seem to have was the music and the wooden toys. I like the music. I have to keep my role here as the consummate brown-noser of Jim Bergman. It was a great video because it demonstrated something that I think technicians do spend a lot of time on, which is evacuation and there's sort of this feeling.

I guess, among a lot of texts, that getting a really good vacuum, you know say getting a 300 micron vacuum is near impossible. I remember that was the case when I started rolling out micron gauges at the place that I worked before. I started my own business, which I guess I'll start by telling this story real, quick. The year would have been probably 2002 or 2003 probably 2002.

I was really hammering everybody to use micron gauges and we had an issue where we had lots and lots of wet systems at this company that I worked. It's a Norma's company and they did lots of new construction and I was in charge of hiring and training new technicians and a lot of what my new technicians were doing. The guys who worked for me we're doing startups on these new systems and we were running into all kinds of wet systems and what we found out was there was two reasons that they were wet and, of course, this was also when 410 a started really becoming The thing - and so we had all these issues with compressors blowing up and shooting black oil all over the place. When I say blowing up, I mean blowing a terminal, so it's pretty extreme and what we found out was one was that installers were pushing copper line.

Sets through chases PVC chases with nothing but the plastic caps on them, and the caps would of course fall off and then there'd be water laying down in the chase, and then they just jam this whole line set full of water. So that was one reason why we were running into lots of wet systems and then the other reason was part of the installation. Protocol was to cap and fill the drain lines to make sure that the drains didn't have any leaks, because we had a lot of second-story air handlers with the fairly long drain lines. And they wanted to make sure that the drains didn't have any leaks, which was good practice initially, when they would rough in the drain in the copper they would cap it and fill it with water.

That was how it was designed. Well, they had some installers who weren't the best with English and when they told them to cap and fill the lines with water, they thought that meant the copper lines. Oh No, so there was entire subdivisions where they were capping the copper pinching and sealing it off and then filling it with water. And I won't tell you what this company ended up doing about this, because it's not what should have happened, but we were running into a lot of wet systems.

That's what I came down to by the time we got there for start-up which is after trim. You know after the equipment had been set and we would show up just wired up and do the run test and commissioning, and so because of this I said, look we absolutely have to make sure that everybody has micron gauges because up to that point nobody, but Me and a couple senior Tech's Adam, and so we made it mandatory and provided a method for everybody to buy these vacuum gauges and they bought the. I think they were sub Co, Sopko or Robin Eyre, I'm not sure which, but they had the little LED lights. That would kind of go off as they went down the scale, and so it was a very it's sort of a loose approximation of what it is.

But it was just going to go off as they went down and we rolled them out the first week and the first week we didn't hear much and then the week after that, essentially every single person brought them back in and said they don't work anymore. And what we found out was based on how they were positioning them, and I learned a lot through this as well that they were. You know they were shutting their vacuum pumps off and without valving off properly and the vacuum pump. Oil was getting sucked into them and laying down in them and they were just getting all contaminated, and so through that.

I learned that. Not only do you need to use a vacuum gauge, but you need to follow a lot of other practices in order to make sure that you don't have a mess on your hands. So that was a really long story to introduce the sort of optimal way of evacuating and kind of why we evacuate in the first place and what other considerations we have when we're evacuating. So that was just me: teeing up the ball there, and so now you can hit it from there.

Well, thank you. That was quite painful for me. What what hearing the mess that we had in our hands? Yeah hearing about refrigerant lines being filled up with water? Just makes my skin curl the only acceptable repair for that would have been to take out the lights, the refrigerant lines right, yeah yeah, and that's not what happened but and I digress. Well, you know this kind of stuff happens more than we care to think.

Probably the best place to start with this is your evacuation rig. We honestly as an industry. I think there is nothing that we have forgotten more or never learned, I would say not even forgotten. I say never learned is the science of vacuum and evacuation.

It is a crazy science and it doesn't work like anything that you would anticipate. So there's got to be some things that, as we talked about we'll, try to explain them in a way that people can get this. But it's a very, very interesting science and it's one of those things in textbooks: they're, they're, so lacking it's ridiculous. If somebody wants just a good primer on this after we're done, there is a page I wrote years ago it's at true tech tools.

If you look up evacuation training or vacuum training on true tech tools, you'll find it it's a good primer to this I'd highly recommend. If you haven't gone to that it's it's there, I think Brian also put a link out on one of his Facebook pages. If you dig around, you might find it there too. At some point: let's start with a evacuation rig.

Probably the most important thing is: don't ever evacuate through quarter-inch hoses again all right. It is a absolute waste of time. I've got a book and I'm trying to find a title of it here, see if I haven't sitting on my desk here, but I think it's called review of vacuum for service engineers is written in 60s by a thermal engineering company. I don't have it sitting here.

So I hope I got the title right. They talked about conductance, speed of hoses and I'll I'll talk about that just a minute, but one of the things they talked about the conductance speed of a quarter-inch hose is so low that we're not even going to discuss it because it's not even worth talking about For evacuation processes, in other words, we're saying who would use a quarter inch hose for evacuation. Yet, as an industry, that's pretty much all we use. Okay.

In my past life, I've worked on some digital gauges and one of the things that people voice - that is oh yeah, I'd love to have a micron gauge built into my digital gauge set and the fact they got chastised for that, because when I built one of The sets I didn't have a micron gauge in there and it's like well, I didn't have a micron gauge built in it's like, because the marketing department doesn't run engineering. That's exactly why because number one, no quarter-inch hoses number two get rid of the manifold. Well, why? Don't we say these things? Well, let's start with this. Why do we have them to begin with? Well, why do we have them to begin with is because we use quarter-inch pressure test point on an air conditioning system, so we hook up that hose.

That quarter-inch line was meant to be a pressure test line, not an evacuation line. When you think about atmospheric pressure, the lowest vacuum you can pull is negative. Fourteen point: seven psi: g, twenty nine point: nine, nine, nine two inches of Mercury's many nines! You want to put on there, it just keeps going down and down and down and down in our industry. Actually, we don't even do deep vacuum.

We get into what they call is roughing vacuum, we're just simply trying to remove atmosphere, air and water out of the system. So when you get into semiconductor industries and vacuum tubes, and things like that, these guys hit vacuum levels that are completely unattainable by the equipment. We use they use things like turbo, molecular pumps and things that probably move ten times the amount of atmosphere that we're removing with the equipment that we use today. So I digress for a second, but if the deepest vacuum you can pull is negative.

Fourteen point: seven psi G right, that's the limitation! It's a physical limitation! You can't go deeper than that in vacuum, so I think some people are going to ask. Well. Why is that? The deepest you can go, and the reason is, is that that's the pressure of the atmosphere that exists around us around the eyes that keeps in the way that we often think of it like it's sucking. Our heads are kind of messed up about that in the first place, really we're reducing below pressure that exists.

Fourteen point, seven is the pressure that's exerted on all of the surfaces at sea level, and that does change depending on where you are. You know sea level and even barometric pressure can affect that based on my understanding, but we can only pull down to where you've that you've removed the atmospheric pressure down to zero. You can't go any below that. It goes back to this always talk about space.

Being a vacuum right and if you're out in space you know between here and the moon, that's as perfect of a vacuum being yet there's nothing in space, it's void of any oxygen, any atmosphere or anything. So how does our atmosphere work right? Well, we got this globe, you know the earth and it's got this atmosphere, that's around and got the suction of space pulling that atmosphere away from the earth. Well, what holds that atmosphere in is gravity right. We have gravity, that's pulling this atmosphere in and the closer it gets to the earth.

The stronger the gravitational pull is so at sea level. We have our highest atmospheric pressure and if we go up on, you know the top of Mount Everest. The atmospheric pressure drops because air has weight, air has mass and air being primarily oxygen and nitrogen. You know primarily nitrogen, that mass is what we're removing we're, taking the atmosphere out of the refrigeration system.

So the only thing in the refrigeration system left is refrigerant and oil. We want to remove all the atmosphere, all the moisture out of that system, so that just refrigerant and oil are circulating in the system, and so when we talk about again what is the highest atmospheric pressure? We can get it well, it's negative fourteen point, seven or 14.7. Psi G is our atmospheric pressure. We commonly consider that zero psi G or, if we're using an absolute gauge that gage, would say 14.7 PSI, and if we pulled a vacuum on a absolute gauge, it would go down to zero psi a if we're pulling a vacuum on a compound gage.

On a pressure gauge, it's psig, it's now negative fourteen point: seven psi G right or just in different units of measurement 29.92 inches of mercury. It's just a different scale that gives us a little bit higher resolution and then you can take another scale on the micron scale. There's seven hundred sixty thousand microns at atmospheric pressure and we're taking it down to you know a hundred microns two hundred microns when we're doing a proper evacuation. So these are just different scales but they're all the same thing.

So, let's go back to that hose for just a minute, and this is a question when I ask you Brian, just to put you on the spot, because you need to be on there once in a while, if the deepest pressure that we can pull is negative. Fourteen point: seven psi G: what is the only way that we can increase the flow? I don't even know if I understand the question properly, but I'm going to say is by increasing the volume you're on the right track there. But okay, if we're to blank off our vacuum pump, the pumps can achieve negative. Fourteen point: seven psi G right, just roughly that's what the pump can pull okay if we want to increase the flow, if the limiting factor is the pressure on a line, how can we increase the flow and turn the volume of gases going through that hose? You have a pick up sound effect at this point.

Sure yeah, oh, let me see now I don't have crickets. I have this, it's not working at this yeah. This is no just. I need anything to distract from the fact that I don't have the answer to this question all right.

Okay, so you have to increase the hose diameter. It's the only way to increase flow is to increase hose diameter if we have a quarter inch hose with 14.7 PSI behind it, and we have a half inch hose with 14.7 PSI behind it. A pressure right and we're squirting water, which hose is going to emit more water or more gallons per minute, if they're, both at the same pressure. Okay right, I get it so those are the larger house guy.

I understand because the pressure can't be changed. It's not like you can put a bigger pump on it and create you know more pressure differential, it's limited in that way. The only thing that you can do is change the diameter of the of the hose to a larger diameter. That is correct and you have just discovered the most fundamental important part of evacuation pump.

Size does not matter. It really is secondary to what you attach to the pump. You know when you have 10-foot 1/4 inch hose and you have a Schrader core in the line. You're pulling about 0.7 CFM through that pump, no matter how big the pump is, if you have a three CFM pump, a five CFM pump and a seven CFM pump, because the most pressure that pump can develop is negative.

Fourteen point: seven, the limiting factor becomes the evacuation rig that is attached to it. So if you're using quarter-inch, hoses and you're not pulling out Schrader course, you may as well have a 1 CFM pump, because if you put a 15 CFM pump on there, it's not going to happen any faster, we're bound by physics. And this is what everybody forgets. Manufacturers of pumps even forget this.

You know how many manufacturers, it's very interesting, I'm going to give a peon a little plug here, because they were the ones that really reintroduced the industry to oversized evacuation hoses right date, Boyd discovered this. The thermal engineering uh catalog thermal written it back in the fifties. Sixties. I think it was a book Dave's dad had and Dave really reintroduced the industry to this, and it was some things my father always knew this.

I think it goes back to my listen to one of your podcaster over with Dan Houlihan, who was the guy. He said. Why did you do this? He goes well, you know, because I I've always known it right and it's like that was sort of the way. My dad was my dad always used oversized evacuation hoses, but my dad did chillers, you know 700 tons and up and I'm like you know, I figured well.

You do big chillers. You just got to have big hoses, but he did that because it would take a year to evacuate a chiller through a quarter inch hose right because at 0.7 CFM you're not going to get the job done. But going back to this for just a minute. The evacuation rig is by far the most critical element of attaching your vacuum pump to the system.

So the first thing you want to do is number one eliminate the manifold completely. You do not want to have a manifold gauge system attached to the system when you're doing the evacuation, you need to first of all attached it with core tools. Core tools simply lie to remove the Schrader core. The Schrader core is a restriction.

We're going to take those core tools and we're going to take the cores out, set them aside, we're going to attach that vacuum pump with to either half-inch hoses or ideal. You could go with with three-eighths, but half-inch hoses are ideal. We're going to attach it with two half-inch hoses and you're going to attach that directly to your vacuum pump. We want to be able to use the core tools to isolate the evacuation rig the system.

You know from the refrigeration system when we do a decay test on our vacuum, which we'll talk about in just a second here now. Some people will ask you, you know they'll say well, wait a minute that quarter-inch fitting isn't that going to slow the flow down, and the answer is absolutely not that small quarter-inch fitting will not have near the effect as the friction of the hose. What we're talking about now is conductance speed of a hose and conductance speed simply is a measure of how fast we can move gas through a hose. The smaller the hose is the higher.

The friction is in that hose. It's the same thing. If we talk about undersized electrical conductors or undersized water pipes, if we're going to get the same flow out, it's either got to be at a higher pressure right or we got to use a bigger hose and we're talking about evacuation when we get down into the Below a thousand micron range we're talking about pressures that are point zero to, let's say psi: we're talking about tiny, tiny, tiny pressures. So, in order to get that gas to move through that hose, we have to have a hose that has a very very low resistance and that low resistance comes from having a larger interior diameter and allowing that gas to more easily flow out of the hose.

Do you have it up to there Brian so we're eliminating the manifold we're connecting with two large diameter hoses from our core tools straight back to our vacuum pump, because the limiting factor of your vacuum pump is the what diameter of the hoses diameter of the hoses Right and other restrictions that are in the system again, we talked about Schrader course. Those are also huge restrictions in there right, probably greater right, I mean Schrader cores are probably a greater restriction, even the hoses. Actually, that is incorrect. Okay, the quarter inch hose is.

I would have to look at the math. You might be right we'll do that as a video sometime I'll do with them without the Schrader course and we'll do quarter-inch and half inch hose to see which one's a bigger restriction. So it could be right, but I'm thinking actually the hoses play a bigger factor in this than the Schrader course do is what my gut tells me. So the trader cores are a greater restriction in the traditional sense, meaning it's a smaller orifice, obviously, but by the time you take into account the length the hose.

That's why it's the it's the length of diameter that plays the biggest factor in evacuation. Here's the next dirty secret and evacuation everything leaks, okay, hoses leak, even copper, leaks at a molecular level. It just it's such a low level. We don't really care about it.

I say for our purposes we would say: probably coppers leak-free. It says leak fliest, we're ever going to get for what we do, but everything leaks, especially hoses and especially evacuation, manifolds or manifolds. We need to isolate those from the system, that's what the core tools are for. So when you're, attaching your vacuum rig and you want to use a core removal tool to attach your micron gauge to the side port, not to the end port, but to the side port up to the core tool.

Okay and you're going to connect your vacuum gauge with a brass connector or a copper connector. You don't want to use a hose in this case, what we're trying to do when we close those two core tools off we're isolating the evacuation rig from the system, because that evacuation rig is made with rubber hoses and rubber gaskets and all kinds of things that Leak and luckily the vacuum pump can overcome the leak rate of the hoses and still pull down the system. Okay, but when we're doing a take a test which means we've closed those core tools off and isolated the vacuum. What we're doing now is we're seeing what is the ultimate level of vacuum that's been attained.

How deep is that vacuum? Is it maintaining that vacuum? You know once we've isolated and you know that's where you get into decay and decay is simply when we isolate the vacuum pump. You know, let's say it's down at 100 microns and we isolate it and it creeps up to 150 microns and then stabilizes. It's decayed 50 microns all right and that's okay. You know as long as we're below 500 microns it's ideal, but you can't over evacuate a system and again you want to use those core tools to isolate it.

When you get down there and literally, if you just pay attention to these couple, things large diameter hoses, remove the cores attached to your vacuum, pump directly you're going to cut your evacuation time down from hours to literally minutes and we're talking a factor of 16 times Faster, so you know, if you think about that 16 times faster. What's taking you an hour to do, takes me a matter of minutes right, that's a good thing! I'll! Tell you this at the end of the day. You know some guys are go! Oh well. You know I I don't need all that stuff.

I just go ahead and hook my vacuum gauge up and you know sweat. My copper first get, the line set set, do the coil and then you know it can run for an hour hour and a half two hours. I don't care. You know I got other things to do on the job.

Well, I'm waiting for that vacuum to pump to run well a couple of things on that number. One is why do you want to wear out your pump? What's the point and let the pump run all that long when you could be running that pump a much shorter time getting the job done a whole heck of a lot faster number two is how many times you've you ended the job at 3:30. You know and 3:30 you go out there, you're going to go, cut the charge and you figure out. You got something going on.

You got a leak in your system. You got moisture in a system, you got something going on there and all of a sudden. You realize crud now I got to wait around for another hour, two hours so think to evacuate, or now I got a blown nitrogen through Andry praise, the thing and go all through this process and get everything out we're we could have figured that out way way. Earlier in the process of the day right because at the end of the day we all know there's technicians, they're going to say you know what a thousand is good enough.

I'm cutting the gas in and I'm going and that systems not going to last as long there are advantages to being able to do stuff faster and the big advantages we don't have to waste time, especially when we don't want to waste time doing it well. Just doing these couple things you're going to find out very quickly, it's going to take a lot of the pain I think out of the process as we go, and one thing that I think Tech's miss because you know my brother and I have this consistent argument Where my brother is a great technician and he does things the right way, the bulk of the time, but he has his argument with me about going direct to the pump and using larger hoses and all this because he's about I've always done it this way, and It works okay, but I think the thing that you're missing are a lot of technicians are missing. Is that it's almost impossible to do a good decay test if you're doing it the traditional way. So let's say you even feel okay with how long it's taking well.

First of all, you're not going to be able to get to leak detection as quickly when I say leak, detection, making sure that you don't have leaks or you don't have a wet system, you're not going to get to that decay test as quickly and so you're. Going to find out later too late, you have an issue, but I think the reason why a lot of texts don't see the value in it is because they're not doing this test at all. So they're not doing the valve it off see how it does test. They're literally pulling down to five hundred microns another 5-hour micro and shut it off or at least the charge move on right or you know or charge.

The system move on, but you're missing a very important step because you can pull down to five hundred microns, say and still have a wet system, and this is something that I didn't realize. I don't think he up until the last few years. Would you quickly just go into that like what is wrong with the system where guys just pull down to five hundred microns shut up their gauges, release the charge all right? Well, first of all, let's talk about a couple things here, because I think people forget about some fundamental things all right. Let's just talk about a return in a room: okay, let's just do a better analogy here.

If I gave you a straw and I'd set up a birthday cake, two foot in front of you, you know even a foot in front of you. I gave you a straw until you blow out that candle with a straw pretty easily done right. You could blow that candle out, not a problem at all. Now, if I lit the candle again - and I tell you now - suck the candle out with a straw right it'd be impossible.

There's no way you could suck hard enough on the straw to suck the candle out. Well, why is that? Why can we blow a candle out, but we can't suck a candle out through the saw? Well it all comes down to this. Is that air in a vacuum pulls from a localized area, so you're not going to pull air across the room? You're not going to pull the air wave and using that straw you're not going to pull it from a foot away and suck that flame out off? That candle it's impossible because air is going to pull from a localized area now understanding this. This is again another fundamental thing: don't ever hook your vacuum gauge up at your vacuum pump you're, not measuring the pressure at the far end of the system, you're measuring the pressure at the vacuum pump again, it'd be like cooking.

Your vacuum gauge up to the straw. Is there a negative pressure on the straw? Absolutely then, why isn't the candle going out because there's no negative pressure at the candle right? It's the same thing: when we're pulling a vacuum, we have to be able to isolate the vacuum gauge from the bomp to test the decay, in other words, to see how deep the vacuum actually is, because the vacuum at the pump is not indicating how deep the Vacuum is at the system and especially at the far end of the system. Some guys will tell you you know. Well, you need to sweat in a pressure port if the external equalizer in your TXV or you need to have something inside to hook your vacuum gauge up inside yeah.

That's a good way of doing it. It'll tell you that your vacuum in the house is getting to a certain death, but that's exactly the same thing you're doing when you have cor tools and you can isolate it right when you shut those two core tool, valves or basically just ball valves, their vacuum. Rated ball valves when you close those ball valves off what you're doing is you're allowing the vacuum to stabilize. You may see the vacuum and go up a little.

You may see the vacuum go down. A little vacuum can do some crazy things, but it's stabilizing that vacuum in the system and as that vacuum stabilizes in the system. What you're going to see is what Brian was on, which is the decay, which is how much different is the vacuum now than it was before. I isolated the vacuum ring with my core tools and we want to make sure that when we isolated it stays below the 500 microns.

When you're reading 500 microns at the pump, you could be at a thousand microns or even 2000 microns. If you're using quarter inch hoses at the system, there is absolutely no guarantee that system is anywhere near dry enough when you're measuring vacuum at your pump. Why did they put that quarter? Inch tap on top of the pump, because marketing was running engineering right because some guys saying well, I can't hook up with my hoses. I have quarter inch hoses.

I need to be able to attach a quarter inch hose to my pump again get rid of the quarter inch hoses and cap that fitting off, because the only thing that fitting should be used for the only thing is testing the performance of your pump to see. When you valve it off, how deep can your pump pulling your pump should be able to pull down below 50 microns below 25 microns is ideal. It'll take a few minutes to get down there don't front about that either. Let it run for a few seconds, but that's about the only thing that fitting is actually used for so we isolate that vacuum from the system and it equals out that's what the decay is and that's where we want to see below 500 microns if you're cutting It off too early you're, making a huge, huge mistake.

That's going to lead to a short life of that system. Yeah because also is let's say you have moisture in the system. I mean you know. Neil Caporetto just did a video about how you can even create ice in some lab conditions, probably not a real practical thing in a normal system, but that can even occur where he was pulling down below 500 microns and he actually had ice inside his little mason Jar right there, you could see it.

There was moisture there and you could see on his gauge. It was said five hundred microns because as water is evaporating as its boiling inside the system, if you do have any moisture in the system that happens over time and all that moisture isn't right there at your port. It's not like it happens, instantaneously. It's a process, and so let's say you have some moisture, that's in your compressors in your evaporator coil or in your line set and a chaser or whatever and you're pulling a vacuum in the actual CFM at the pump itself has overcome that and pulled it down.

Unless you valve it off and watch that decay rate you're not going to know that you still have a wet system now when soon as you valve it off, if you do have a wet system, it's going to go up a little bit at first and then It's just going to keep rising, it's not going to stop rising until it gets up to the boiling point of water. At that particular temperature. You bring up another very important point, your absolute genius - and that is this. There are no significant flows in a vacuum or during the evacuation process, and I want you to think about this one for a minute.

A lot of guys think we're going to suck the water out of there does not happen if you were to take and put a drop of water at the far end of a coke bottle, all right and then suck on that coke bottle, no matter how hard You're sucking that coke bottle that drop of water is not going to move it's going to sit in that coke bottle right at the bottom. You can't suck that drop of water out, it's absolutely impossible. So how does the vacuum pump remove it? Well, the vacuum pump lowers the pressure and when it lowers the pressure, we lower the boiling point and the heat that's in the bottle and in that water starts to cause it to boil violently right and it changes state and as it's changing state, it absorbs heat From the bottle and absorbs heat from the water and that water actually gets colder and colder as it goes, and so what you're going to see if you were to actually measure the temperature of that drop of water is as soon as you vacuum on it. It starts to reduce the temperature because of changing state well as it reduces in temperature.

It also reduces the amount of evaporation of that water. It starts to evaporate slower and slower, because the lower and lower temperature. So as we pull a vacuum on a system - and we change the state of that water as it starts to boil away and absorbs heat, it's going to take longer and longer and longer to remove it because it's getting colder and colder and colder and colder. And it's not evaporating as fast now, eventually it gets so cold that it actually turns to ice and the freezing point of water is 32 degrees.

There's some science that says you know it changes slightly under vacuum but for all intents and purposes, at 32 that thing's freezing now the question becomes, is well once it hits 32. Does it continue to get colder well? Is it changing state still absolutely, but at this point we're changing from a solid directly to a gas because we're not evaporating anymore we're sublimating. At this point, the moisture has stopped boiling because it's frozen and now we're changing directly from a solid to a gas, and then it takes a huge amount of time to remove that ice at this point from the system. Now we stop and think about this.

For a minute, because this ice evaporate well, those of us that are old enough, I think Brian and I are - and probably some of the people listening will be cold enough to remember ice cube trays in refrigerators in ice cube trays, you'd, pull out, look like old Ice and it used to have that all the edges around it off and I sort of shrunk down and it's like it evaporated right. The ice actually evaporated. You got these ice cubes that are these little tiny round. Funky-Looking ice cubes that also don't taste too good, because they've sucked up flavor from the freezer, but those ice cubes are sublimated ice they've, actually evaporated away.

That's the same thing that happens in a vacuum and just like it took weeks or months for that ice to evaporate in refrigerator. It takes a huge amount of time, also in a vacuum, but once you pull your initial vacuum, in other words, once you move that initial bit of atmosphere up in seconds in literally seconds 90 % of the atmosphere is gone in a couple minutes: 99 % of The atmosphere is gone, and you know just think about this for just a minute, if you did the math, we got 760,000 microns at atmospheric pressure, we're pulling it down to five hundred microns you're talking about fractions of a percent of atmosphere, we're talking about removing that Has a huge impact on system performance we got to get that out of there, don't think, because we got most of it out of there. It's done at this point, but that last little bit of moisture that last a little bit of ice. It takes a lot of time to remove if you get it in there now.

The other thing Brian had mentioned was that we're not going to make ice except under the right conditions. Well, the right conditions are occurring all the time when a we evacuate a system in the winter or in the fall or through when we evacuate a refrigeration system that has a box that has multiple evaporators and is cold. Moisture will migrate to the coldest place in the system. So, if there's moisture in a system, it's going to migrate into that cold evaporator, it's going to sit there until we remove it with our vacuum pump and because we have this cold evaporator.

A good practice is eternal defrost heaters during the evacuation process to help worm that I've operated up to drive that moisture out of the evaporator melt any ice, that's in there. These are things that refrigeration guys deal with all the time. So we've got to make sure that our conditions right yeah they can be, and they can be right for air conditioning technicians. They can be right for refrigeration technicians to make ice in a vacuum and it absolutely absolutely does happen.

So here's what I was meaning to say - and I said that completely inaccurately. Thank you for pointing that out. What I meant to say was a lot of technicians now are using the creation of ice as a reason not to pool fast vacuums. Not to do your evacuation quickly, so they're using that as an argument to say: well, don't use large diameter hoses, don't do this stuff, because if you pull your vacuum too quickly, it's going to cause you to form ice and the cases in which pulling the vacuum Quickly versus not quickly will cause ice to build up that being the deciding factor are very rare, it being due to the fact of ambient conditions, being you know, below 32 degrees or near that temperature.

That's very it's common and all good argument. It's not even a good argument, because this is physics, this isn't magic, it's physics, and if we make ice, we can tell that with a vacuum gauge, especially, we use a high quality vacuum gauge like the akka tools, vacuum gauge. It has high resolution and high accuracy that we can definitively tell the difference between moisture and just general pressure in the system. All you need to do.

If you get moisture in a system is break the vacuum with nitrogen, let it set them in a torn back up and then pull it down again. The key is warming that moisture back up. You know we talked about this earlier once you start pulling the vacuum. The water starts changing state and getting colder once it gets colder.

It takes longer to remove it, doesn't matter whether this quarter-inch hoses half-inch choses, whatever once it turns ice, it even takes longer to remove. But if we break the vacuum with nitrogen, it's going to effectively do the same thing. It's going time to warm up and then gases remove extremely fast out of a system. So when you put nitrogen back in the system, not going to hurt a thing, it's going to come down very quickly when you have moisture in there, it's going to take time and there's nothing more important than keeping your line sets clean and dry.

When you're doing your installation absolutely nothing more important, so you need to make sure that if you're not going to install that condenser that those lines are capped off or soldered shut or braze shut, so that moisture cannot bond at a molecular level to that copper in There again moisture will condense on cool surfaces, so it will condense inside copper tubing and then it takes forever to get that system dried out and then there's one more thing: Brian and we're coming up on the time here. I want to make sure that I cover one more thing that is really important, that I think frustrates a lot of guys out there with vacuum gauges and that is residual refrigerant in the system. Little experiment: next time you get out your vacuum gauge, take a tank of gas and just take a tiny bit of refrigerant, just purge it into the tip of your micron gauge, okay and watch what happens? Exposing your vacuum gauge to refrigerant is going to make the vacuum gauge act radically. It's going to make that gage probably go down to 600 3,600.

Some kind of a micron range really low, you're going to be surprised when you hit that. But this is a tiny bit of refrigerant vapor. Well, why is that? Well, vacuum gauges, work off thermal conductivity and air or nitrogen is what those gauges are typically calibrated for refrigerant has different thermal properties than air and nitrogen does, and it's going to affect the way. The gauge reads and a heavily refrigerant Laden atmosphere.

The gauge is going to not read as accurately as it does once you get that refrigerant out now realize that if you're taking a system that you've just recently serviced like, let's say you change, not a TXV and you're pulling the vacuum back down again and there's Refrigerant oil are miscible and there's refrigerant boiling out of the way on the compressor or not of the condenser or not of the piping and all that stuff. As you draw that vacuum down, there's less and less refrigerant in the system, you're, basically degassing that system. It's going to be the same as if you had air in the system, in other words, well, the vacuum readings won't be the same at atmospheric pressure as they come down, they're going to get closer and closer together because, ultimately, we're removing the atmosphere out whether it's Oxygen atmosphere, nitrogen atmosphere or refrigerant atmosphere, nitrogen and oxygen together, please don't ever add oxygen to a refrigeration system or you'll kill yourself. Oil and oxygen is do not mix, but as we pull this system down as we pull this vacuum, they're getting closer and closer to the same.

So sometimes what you have to do is you have to if your vacuum gauge is seeming to stall, if you're getting Radek readings on your vacuum, gauge break the vacuum with nitrogen and then let it set for a minute and then start the evacuation again that nitrogen Will pull out some additional refrigerant with it and it'll make the gauge start acting normal again? Sometimes you just get a roll of refrigerant Laden atmosphere. The other thing you need to make sure of is that for sure I've seen this happen more times than one. Your core tool needs to be fully opened by your brass connector on your vacuum, gauge that sometimes that happens where the core depressor is not fully. That's not out far enough, where it's not opening up the court presser on the side port of the court tool.

So you can either a remove that thing out. If you want to remove it out because again vacuum gauges like the active tools one can handle up to 500 psi. So you're really not going to hurt anything or you can. You know just make sure that the depressor is actually physically to pressing it in far enough, but again a port note here: vacuum gauges are calibrated with either air or nitrogen and, if you're not in that atmosphere, you can affect the readings that your gauges and a Lot of guys, don't realize that simply breaking the vacuum with a little nitrogen will resolve that issue.

We need to start the evacuation again. You kind of answer. The question that I had is this is, to my shame, because I haven't looked this up myself, but you mentioned that the IQ tools, micron gauge - allows it to be pressurized. Are you aware of any micron gauges that have an issue if refrigerant pressure is applied, because that comes up a lot? My technicians have asked: well, I'm done with my vacuum and I need to release my charge a charge.

The unit am i safe to do that with the micron gauge, I'm still installed on the side port because, obviously, if they remove it from that straighter than you just lost your whole vacuum right there. Basically, whatever you do you're going to lose your vacuum. If you change that micron gauge configuration, it depends on the vacuum gauge and the manufacturer. You really have to look at your manufacturers, literature and see, first of all, a couple of interesting notes: they're, a good designed vacuum gauge only has one port on it.

A lot of them you'll see dual ports on there and they did that, because technicians wanted hook to quarter-inch hoses in line, so they could have the vacuum gauge in the line. Again, that goes back to marketing working for engineering, not a good idea. You want a man on those initials up goes. That was another thing they did.

Is they? Everybody was trying to pull through them and it was horrible. I mean it didn't work, absolutely will not work and then you're really going to contaminate your gauge especially put refrigerant oil or anything through there. It's a nightmare. So, even if you have a gauges, got dual ports on their cap, one of them off and connect the other one directly to the side port of your core tool.

That said, there's no flow into that thing right as soon as you release refrigerant. In there, the pressure is only going to go part way up the stem, and then it's going to sort of stop going into your vacuum gauge, because there's no outlet, if there's no place for the gas to get out it, really can't get in and contaminate that Sensor nurse don't worry about subjecting that to a little bit of pressure, it's not going to hurt anything, but you have to see how your manufacturer rates that vacuum gauge, because some of them will not handle pressure at all. You know like the old thermal engineering ones, they'd handle about 30 to 50 pounds of pressure on there and if you got anything higher than that, you're going to you know blow the back into the unit out because it's not a pressure rated device it realistically. When I'm doing an evacuation, what I do is, I usually connect the liquid side of the system and I very slowly crack open my suction service valve and pressurize the system very slowly and when it gets up to 1 or 2 psi I'll.

Take the gauge off because at that point, what I'm trying to do is just make sure that I've got enough pressure on a system that I can actually know it's above atmospheric pressure, I'll take my gauge off the system and then then go from there. It really depends on the manufacturer. You know here's one thing to close with think about this, for just a second, how many of you guys have had somebody out to service your refrigerator? I would care to say it's almost none of you right. If your refrigerator doesn't work, how many you guys would run out real, quick and get some piercing valves and throw them on there and check the charge.

My guess is none of you right well. Why does that refrigeration system run for 20 years? Why can it run for 20 years sitting in your garage chugging away keeping your beer cold? We can't make an air conditioner lasts for 1 or 2 years, sometimes without a breakdown, and it's because it was factory, evacuated and charged, and it was done in a way that was correct and if we do proper evacuation in charge. In my opinion, if you do it right once, you should never even check the charge again on that system. There's no reason to ever put gauges and on that system again, because the refrigerant should never leak out the only time we need to connect gauges when we have a leak and it's a whole other discussion, but think about this.

For just a minute units can run for 20 years air conditioning p-tech units window units, whatever all of us have worked on us stuff. How come that stuff can last forever, but our stuff doesn't - and it all comes down to because they did the job right and if we start to do the job right, we're going to see exactly the same things important things to think about as you move forward. Just attaching and removing gauges all the time is not a particularly good thing to be doing. You have the potential of adding in air and moisture every single time.

You do that. If you don't purge your hoses, you want to talk about a chute by the hip procedure. Purging hoses is probably the most. You know just haphazard thing that we do, which is kind of it's.

Okay, that's about right, and then you move on. It's not a great practice that we have, but it's what we have to rely on, but we're going to come to a day where all the sensors are going to be inside the unit or majority of them. And we can do it right the first time and then we can just monitor without having to connect and disconnect, which is a future that I, like, I think some guys might be scared wow. You know, I think again, that's craziness right because I haven't had a pressure transducer, my refrigerator since I've been a kid and I've never needed to know what the pressure isn't a refrigerator.

It just keeps working and it's that stuff we don't need to add. We don't need to know pressures, temperature, superheat, sub cool. What's the thing is charged and charged correctly, the biggest part of our job is removing dirt. Keep the evaporator clean.

Keep the condenser clean. Keep the compressor clean around that you know check electrical components. Do we need to know that information? No, we really don't it's not it once the charge is right, it pretty much stays right and we will always always always need field equipment to test stationary equipment. We've had stationary stuff forever in factories and then industry and all that stationary equipment has to go through periodic calibrations and tests to make sure that it's accurate and putting a pressure transducer in a system and expecting that the last 20 years is ridiculous.

It's under a huge amount of duty all the time, and while these things again they sound good and they sound like great solutions. Do we really need them? I say no so forget. I ever brought up the transducer thing: yeah! Well, just well, hey we're seeing equipment! Come out, I just saw some new, I want to say it was York, maybe came out with a new unit that gives you all that information, a carrier Infiniti has been giving us that for years I mean the one in my house. I just go.

Look at the thermostat - and it tells me most of this information doesn't give me sub cool strangely enough, but it gives super heat and pressures and yeah it's cool, it's cool for sure I mean it's cool stuff, but again it goes down to. If you don't know what it should be, what difference does it make what it is right, if we're going to we're going to make measurements without knowledge, what difference does it make what they are? It is what it is: it's a function of the load so having that at our fingertips is only as good as the other information we have at our fingertips to know what that reading should be all right. Well, why don't we get this one wrapped up Brian and look forward to talking in the next one? All right sounds good thanks, Jay all right! Well, thank you for listening all the way to the end. If you haven't subscribed to this podcast on a podcast app on your phone, then you're really missing out.

If you have an iPhone, you already have a podcast app right on your phone. You can subscribe there by just typing in HVAC. If you have an Android phone, you can download the stitcher app and search HVAC and do the same thing subscribe there. One thing that I wanted to mention here just because it's it's very pertinent to this conversation is a lot of people.

Think like I'm, a big proponent of digital gauges, and I am but I haven't always been, and actually I'm very much prefer analog gauges. I know this is sort of a like what is Brian talking about this for, but I wanted to just bring this up, because whenever we talk about evacuation, one thing that I think we can easily miss is the practices before evacuation, which is nitrogen, pressurization and then Also, breaking your vacuum with nitrogen, but specifically when you're first doing your pressure test, you want to make sure that you don't have any leaks before you go into vacuum and one thing that I found since we've started using digital specifically either the test of smart probe Test o 550 or test to 557. Those are the three that we use in the business. What we're finding is we're having many much fewer leaks, because when we pressurize up to say 300 psi we're doing our standing pressure test, we're able able to see very small changes on the digital gauge that we may have missed previously with the analog.

So that's one thing that I want to just sort of mention in general: is digital gauges. High-Resolution digital gauges can help you find leaks before you go into vacuum, which can help to save you a lot of time, because you don't really want to be finding now that you have leaks in vacuum, because then you're pulling moisture in you're pulling air in not A good thing, and so a good set of digital gauges can help you with that. Many of you know that I sort of partner with true tech tools. It really is just as simple as I met bill and I really believe in true tech.

I believe that they support the product really well I mean so. Bill gave us an offer code, which is get schooled all one word. So if you want to look at a good set of digital manifolds, I would suggest that you go to true tech tools. Com have a look: there you'll find that their prices are very competitive, but even more than that, they really really support their products and they're a company that really supports the industries with training and help, and just does a lot of good things.

So I would encourage you to look at that and then also, as always, hold a good vacuum and keep your system dry until next time on HVAC school.