How to Evacuate an AC system, Full Vacuum Procedure

[Music] as I start talking about vacuum pumps I want to pause real quick and just let you know that I've teamed up with my buddy Paul over at the engineering mindset channel for a video where he's gonna run you through the inner workings of a vacuum pump and how it actually works as well as some animated models so you can visualize and build your understanding of the pump itself so please check that out down at the links below and subscribe to his channel engineering mindset hey thanks for watching this complete procedure video for evacuation or vacuum for air conditioning refrigeration systems first off why do we need to pull a vacuum well the goal is to get everything out of the system that's the copper lines evaporator condenser compressor all the components of that system everything that isn't refrigerant or oil needs to be out of there and air has some things in it that we really don't want in there namely water vapor and oxygen but even the primary constituent of air which is nitrogen we don't want it in the system because it's what we call a non condensable gas it's not it can't be condensed it doesn't change state and so it results in poor system performance and capacity but especially oxygen and water vapor can result in corrosion and reactions inside the system that can be both harmful to the system and ultimately even dangerous so first let's establish that there really isn't any such thing as vacuum vacuum is just the absence of molecules so when we have our atmospheric pressure at sea levels 14.7 PSI air or pounds per square inch absolute that is the pressure that our atmosphere exerts on us in all directions when we're near sea level if you go up into the mountains that pressure is a little bit less but either way we always have this pressure and that pressure is exerted by the stuff that makes up our atmosphere and namely our air which like I said it's primarily nitrogen but also contains some other components such as oxygen argon co2 and water vapor as its primary constituent parts which with a bunch of other stuff in there we do not want that inside the system so what we do is is we create a negative pressure so that way the molecules from inside the system move out and we use a vacuum pump in order to create that negative pressure causing those molecules to push their way out so while we think of a vacuum pump as sucking really what it's doing is creating low-pressure and then those molecules are actually forcing their way towards that lower pressure so very simply rather than thinking of it in terms of being sucked out think of it as they want to come out those molecules want to come out of the system when there's a lower pressure outside of the system and the lowest pressure that we can create is at the vacuum pump itself so our goal is is in everything that we connect to that system to make it as easy as possible for those molecules those air molecules to get out of that system out of that copper out of that tubing and into our vacuum pump now in vacuum we measure in very very small units of measure and those are called a micron and a micron just means one millionth of a meter of mercury column we're using mercury column as the measurement in this case and so a micron is literally a tiny tiny tiny measurement of pressure at atmospheric pressure is 760 mm microns equals atmospheric pressure so we have to go from 760 mm microns down to something much lower and industry-standard is typically about 500 microns so you can see we have to create a pretty significant pressure differential in order to get from atmospheric pressure 14.7 PSI a or 760 mm microns down to 500 microns or even lower and so we've got to have a properly functioning vacuum pump first off in order to do that now before we even get to the vacuum pump in order to pull a deep vacuum in order to get those molecules out we need to have a clean dry and tight system which means that before we even get to the stage of hooking up that vacuum pump hooking up our hoses we want to make sure that a we don't let unnecessary water get into the system we don't leave the lines open any more than we need to and we keep any solid contaminants out of the system because a vacuum pump is not going to remove solid contamination it can boil off liquid water but it's time-consuming and it's not something that you want your vacuum pump doing you primarily want your vacuum pump removing that air and water vapor so if you're working in rain if you're working in a situation where your copper is going to be open for a really long time you want to make sure that it stays completely sealed and that while you're working you are purging and then flowing dry nitrogen in order to make sure that you're not getting any unnecessary moisture or contaminants into the system so let's talk quickly about purge then flow and all that means is is that when you're working with copper tubing which is primarily what we work with it might be aluminum or some other material but generally we work in copper you want to first purge your lines with dry nitrogen to fill those lines with nitrogen and then you want a flow nitrogen wall your brazing and this is going to help prevent the build-up of cupric oxide or copper oxide inside your lines which are basically like little copper flakes that come off of the copper when heated in the presence of oxygen which brings us back to this whole subject of oxygen we really want to keep oxygen and water vapor out so while we're working and we can't quite have a vacuum yet because we're in the process of brazing or fitting our tubing together assembling our system we want the system to be full of nitrogen rather than air that contains that oxygen and water vapor so step one is make sure that the system is clean dry and tight step two is to make sure that the system is leak free before connecting the vacuum pump your vacuum pump in your vacuum are not there to help you find leaks now we do a process to make sure that you aren't leaking under vacuum but before you get to that stage you want to have purged nitrogen then flowed nitrogen while working and then you want to pressurize the system to ensure that you have no leaks so the best procedure there is to pressurize the system to whatever the system design test pressure is then do a bubble test on any filled joints that you've made to ensure that you have no leaks let that stand depending on the application anywhere from 20 minutes up to a couple days depending on how mission-critical it is to make sure that you have no leaks but the result is to ensure that you have no leaks so now we're pressure testing using the Java link probes from field piece and the measure click app to make sure that we're not dropping pressure even after visually inspecting all of the joints pressure testing to make sure that the system is completely leak free is critical before you attempt to pull a good vacuum because this is a system change out we're only pulling on the evaporator coil in the line set and so we're gonna pressurize to the low side test pressure which is 250 psi or there abouts so one thing you'll notice whenever you're pressurizing a residential system split system you'll notice that as you add in pressure to the high side eventually it will stop and the suction pressure the section set will stop going up and that's when you have a hard shut off txb so it'll often list as hso or non-belief and what occurs is because the external equalizer is the closing force for the TXV eventually that will overcome the opening force of the bulb and won't allow any more flow through so at this point we've set it right in at just under 250 psi and we're gonna monitor it to make sure that there are no leaks I do have to give a caveat here when we say leak free no system is leak free every system leaks tiny tiny tiny amounts even if it's just the at the molecular level so anytime you have any mechanical fittings threaded fittings things like flares where you have a press fitting between copper and brass there are going to be microscopically in those points and you're gonna find that when you get into deep vacuum and you start to do a decay test so we're not looking for perfection but we don't want to have any clear mistakes that lead to leaks such as a braze joint something like that you are gonna have those molecular leaks and that's something that we just have to kind of live with so now let's get together the tools required for a proper vacuum or evacuation you need a vacuum pump a good modern two-stage vacuum pump that can pull down to 50 microns or below when isolated with a micron gage you need a set of hoses now we recommend using large gauge hoses and preferably hoses that you only use for vacuum versus for refrigerant delivery because when you use hoses especially for things like recovery they tend to become contaminated with refrigerant refrigerant oil and it makes them more difficult to pull a deep vacuum with we say large gauge that means larger than quarter inch 3/8 half inch or 3/4 inch the bigger the better when it comes to hoses because we want to make it as easy as possible for those molecules to come out of the system and go into the vacuum pump we also are gonna need a core remover tool and the reason for that is is that many systems especially residential or smaller systems have Schrader valves in them and a Schrader valve has a very very small opening it's like a valve on your tire and so when you depress that Schrader it only opens a little little tiny port that doesn't allow much flow through and that's a huge restriction limiting the speed and the depth of your vacuum so you want to use a core remover tool to get those cores out which is gonna greatly increase the speed of vacuum then finally you need a vacuum gauge a good quality vacuum gauge that reads down into the micron scale it has to be a good modern vacuum gauge you cannot use something like a compound refrigerant gauge the blue gauge doesn't have near the accuracy that you need the example that Jim Bergman always gives trying to measure vacuum with a traditional gage is sort of like trying to measure inches on your odometer in your car while your odometer does measure distances it's designed for larger distances and so in the case of your refrigerant gauges they're designed to measure a PSI at a time not a micron at a time a micron is a tiny tiny measurement of pressure one millionth of a meter of mercury column like we discussed before so whenever measuring a vacuum you have to use a vacuum gauge often called a micron gauge so this is a quart remover tool corer remover in the inside and this grabs that Schrader core and these jaws holds it out using system pressure but also it kind of just grabs the head of the core and when you connect your vacuum you want to connect here when you're sealing off for isolation purposes either with refrigerant or when you're under vacuum doing your decay test that's when you shut off this valve but you can only do that with this or remover out when it's in it can be shut so the way you remove a core is as follows back out the plunger install it on to the service valve place it over the core make sure that this handle is all the way open as you do this all the way then you pull it out and there is our Schrader core in typical applications the Schrader core is depressed with a core depressor inside the hose a quarter inch hose and the internal volume is greatly restricted okay so now we're ready to do our evacuation the first thing that you want to do is you need to confirm that your vacuum pump is working properly and before you even connect it to power check that oil in the vacuum pump if you haven't changed it recently you need to change your oil in your vacuum pump which is very easy to do first thing you do is you warm it up you run the pump isolate it for just a little bit so it warms the oil up shut it off drain the oil as you're draining the oil you want to fill it with a little bit of clean oil while the dirty oil is coming out just to make sure that you get all of that dirty oil out and then fill it up into the proper fill level on the sight glass of your vacuum pump you always want to visually inspect your oil as well to make sure that it doesn't show any signs of cloudiness or contamination which can be an indication that that oil has moisture in it from a previous evacuation or from being left open you always want to store your vacuum pump sealed up so that way water vapor from the atmosphere can't make it into your vacuum pump once you know that it has nice clean oil in it then you want to connect your vacuum pump just to a micron gauge and you want to ensure that that vacuum pump pulls down to below 50 microns fully isolated now some manufacturers will say a hundred you can look at what the ultimate pulldown rating of your particular vacuum pump is but I like to use vacuum pumps that pull well below 50 microns in a matter of a few seconds if you connect it and it's only pulling down to five hundred microns or so then that shows you that you're not gonna pull be able to pull the system down that low if you think of vacuum like a hill those molecules have to fall into the pump from higher pressure to lower pressure so if your pump can't pull down to a very very low micron level by itself then you're not going to be able to get those molecules out of the system and you're gonna have a really tough time pulling a deep vacuum another feature of your vacuum pump that I want you to understand is your gas ballast a lot of manufacturers or technicians will advocate leaving the gas ballast open until you pull down into that deep vacuum stage and then closing it off in practice you can generally leave the gas ballast closed as long as the system that you that you're pulling on is known to be dry if you do have moisture in the system though it's best to pull down and remove that water vapor with the gas ballast open in order to keep from contaminating your oil also another tip if you know that you're pulling on a wet system you can actually leave the gas ballast open once the oil has become moisture and contaminated and that will help to dry that oil back out I've seen several cases where you have creamy contaminated oil and by running it with the gas ballast open it will actually dry its own oil out now keep in mind that a vacuum pump works to remove those molecules out but if you do have liquid water in the system which does occur in some cases that vacuum pump is pulling down to this deep vacuum which is then boiling the water off you're actually dropping the pressure to the point that water's gonna boil because now the boiling temperature of that water is below your atmospheric temperature so he's gonna enter the system and boil that water off now quick note if you have a system that's known to have water in it it's helpful to heat the system with a heat gun especially if you know where the moisture may be and that will help drive some of that out and speed up the process especially when you're working in low temperatures if you're in a low ambient condition just where you live is cold basically or if you're working on refrigeration equipment using a heat gun is a really nice tip to help speed up that boiling of that water out of the system so now you know your system is clean dry and tight you've done your pressure test you know that your vacuum pump is working properly as well as your micron gauge because now you put your micro engage directly on the pump confirm that it's working properly you've inspected your oil you understand how to use the gas ballast now it's time to go ahead and connect to the system step number one is going to be to make sure that there is no pressure on the system before you start to pull a vacuum you do not pull a vacuum on a pressurized system you use your core remover tools to remove the course from the system wherever you're gonna be drawing from now in this case we're going to primarily show a one hose setup and this is because for typical residential applications the one hose setup for a change out situation which is very common case where we need to pull a vacuum is one of the easiest and best ways to pull a vacuum for a standard air conditioning technician or installer you can also do a two hose setup and in that case you would have to remove course from both sides so if you look at typical service valves in an air conditioner you have your suction line which is the big line you have your liquid line which is the smaller line your suction line is going towards the compressor from the evaporator coil and your liquid line is going towards the metering device from the condenser coil so these are the two access points that you have if you're gonna be pulling on the entire system such as the compressor condenser coil and the evaporator are all at once then we suggest two hose setup if you're only going to be pulling on the evaporator coil and line set then the one host setup is generally going to be appropriate so you remove the core from whatever side you're pulling from with your core remover tool you remove the end and that's where you connect your hose going directly to your vacuum pump you'll notice here that we do not recommend using quarter inch hoses and we do not recommend using a manifold when pulling your vacuum the reason for this is that quarter-inch hoses and manifolds tend to be both leaky and restrictive and so we're looking to eliminate leak points that can cause problems with your vacuum and we're also looking to remove restrictions because we want to be able to get those molecules out the easiest way possible now quick note a lot of technicians will say that because the ports on the unit are quarter-inch it doesn't matter that the hoses are larger going to the pump and that's just not true the easiest way to think of this is in terms of a tollbooth on a highway toll booths are very very narrow but there are only a short distance and so while they do act as a restriction to the flow of vehicles you still have that entire highway is much wider and that results in more cars being able to be moved again our goal is to reduce the resistance of those molecules as they're traveling down the law bumping up against the walls and that sort of thing we want to get them out as easily as possible we do want to remove the straighter course and we do want to use large gauge hoses for the fastest possible evacuation and we've done test after test showing that both removing the cores and using large gauge hoses that are used specifically for evacuation or the fastest possible way to pull a good vacuum so now we're connecting straight back to the vacuum pump and we're using a micron gauge on the system itself now what we found to be the easiest way is just to leave the Schrader in on the liquid line this is if you're just pulling on the line set and the evaporator coil and use a brass adapter going to your micro engage with a corded press or on it and attach it to the liquid line and the reason why we do this is that now that's on the furthest point away from the system your micron gauge is now far far away from where you're pulling from which means that when we show 500 microns or less at that point it proves that you have that deep vacuum all the way through the system one of the biggest mistakes that we see technicians do and where they don't get great vacuum results as they connect their micro engage at the vacuum pump now remember your lowest pressures at the pump so you may see 500 microns at the vacuum pump and still have in the thousands of microns on the other side of the system which is why when you connect your micro engage you want to connect it the furthest possible away from the pump as you can in the system itself so if you're working on a large commercial system sometimes you can even find another port on the other side that's going to give you a better indication of whether or not the vacuum has reached that distance you also don't want to use pull through ports on your micron gauge that acts as another restriction it just increases the time of evacuation and this is a significant difference in speed I want to be clear here a lot of technicians may see this and think this is overkill but what we see is on clean dry and tight systems we're generally pulling our vacuums on change-outs in under 5 minutes or many other technicians who are using manifolds quarter inch hoses and installing their micro engages in the wrong place a they're not getting a proper vacuum in the first place because they're measuring it at the pump where it's at its lowest pressure and B in some cases is taking hours rather than minutes so it's a big time saver and you can ensure that you have a deep vacuum when that micron gauge is connected further away from the system and not pulling through the gauge for typical residential air conditioning equipment we want to pull down below 500 microns we want to then isolate by shutting off our core tool going to our pump and make sure that our system does not decay the term reuses decay which means rise in pressure remember a lower micron reading means lower pressure which is what we're looking for some carrier installation guides say pull to 500 microns isolate for 10 minutes and ensure that it doesn't rise above a thousand now our procedure is a little more thorough than that our procedure that we use at kalos is pooled to below 500 microns generally 250 or 300 microns and ensure that it doesn't rise above 500 microns in 10 minutes now the reason why you do this why it would rise at all is because like we said every system leaks a little bit even if it's just around the seals of your core remover tool at your flare fittings at any chat lift connections those sorts of things you're gonna have tiny molecular leaks that aren't gonna result in any significant refrigerant loss over the life of that system but do show up when you're using a micron gauge after you've pulled a deep vacuum because again remember a micron is a tiny tiny measurement of pressure so when you're doing this decay test you can be sure that you don't have significant leaks by watching that decay rate now if you do have a decay rate that continues to go up that means that you either have moisture contamination or leaks there's more thorough videos done by a QED tools and blue vac that will show you some of those procedures but just know that if you have a really quick rise where you are rising more than 500 microns in a 10 minute period of time that you need to address that further now we're gonna use our large aged hose we're gonna use a half inch connector to the pump dedicated vacuum hose with a very smooth bore low permeability surface on the inside which means that it doesn't have any refrigerant oil because it's never been used to transmit refrigerant and so therefore it's going to pool a quicker vacuum and now we're going to so we have the vacuum pump 1/2 inch connector to the large seal clamp that attaches it to the 3/4 inch hose tying into the suction line I'm going to put a cap on that just to make sure that we don't have any leakage whatsoever it's going to pull from the suction line out of the evaporator coil until it gets all the way back to this point then we're gonna read our deepest vacuum right here at this spot ready set initially you pull out a lot the air and nitrogen and then very quickly it's gonna strip you can see the rate at which it's coming down and remember this is the far side of the system so this is the deepest this is the furthest away you can see at the pump itself we're already making a much lower back and that's because the vacuum by scary nature has to be lower than the fruit of the side of the system so that way the molecules move from the farthest part of the system down to the lower pressure so you can see many technicians would think that there already even a vacuum a simple it says come we can see that the horse out of the system was still and see this is a three and a half ton carrier system what system you see here hundred and fifteen microns and that's correct but we're still taking a little while to get them all the cute little car set remember the lower the micron this is a lower vacuum level here which vacuum level is just a measurement really of how many molecules are there are present so there's still more molecules in the curve inside the system when there are all the way back here this is why you never want to connect your micron gauge at the pump or if you can help it even at the side that you're drawing you want to connect your micron gauge as far away from the pump and the hose connecting hoses as possible to show that you're pulling that deep vacuum all the way down on the other side of this alright so we just hit 500 microns on the far side of the system and you can see at the palm okay so now we're down to 377 microns on the far side we're to go ahead and valve off the core remover tool and so that way that separates the clump from the system and now we're gonna make sure that this does not rise and in fact initially it may actually go down just a little bit was really holding 397 rows a little bit of curse the decay rate as well within the allow now with a good quality micron gauge it's okay to actually open up the refrigerant circuit with the micron gauge still attached you have to check the pressure rating of your gauge it is good to leave a kitch upwards when you do this so that way oil doesn't have any chance to run down into it if you're worried about this what you can do instead of connecting it direct is actually do it on the side of a shutoff tool like a quarter press or something of that nature in order to prevent this from hitting the micron gauge what would be three bad gauges another thing to keep in mind when you're pulling on a system that previously had refrigerant in it so say for example you're replacing a compressor or you're placing a condenser coil or a reversing valve something a system that previously was operational and now you're gonna pull a vacuum on it keep in mind that a micron gauge is actually a thermal sensor and it's calibrated to air or nitrogen it is not calibrated to the thermal mass of refrigerant so when that sensor comes in contact with little bursts of refrigerant whether that refrigerant is in the system or entrained in the oil of the compressor it's going to cause your gauge to go crazy for a little bit so just keep in mind when you're pulling on a system that previously had a refrigerant in it and some of that refrigerant may be coming out of the oil initially you may see some jumping readings on your micron gauge and that's normal just continue pulling a deep vacuum until those numbers begin to stabilize there's a couple really big myths that technicians will think when they watch this video or whenever I talk about this one is that you'll freeze moisture in the system by pulling a vacuum too fast and the second is that you'll damage the oil by pulling too deep we'll start with the second one you're not gonna damage the oil by pulling too deep typical system oil like pol in fact requires a very very deep vacuum if you are gonna pull on the oil unless you are pulling below 1 micron which you're not you're not going to damage the oil that is not a concern the second thing that a lot of technicians will say is that you're gonna freeze moisture in the system if you pull too fast it is possible to freeze moisture in a vacuum there's many demonstrations that have been done on this but generally they're done in glass vessels where you don't have a lot of heat coming in to melt that ice as you're pulling down of course it is possible to freeze ice inside of a system when you are near freezing conditions so obviously if it's below 32 degrees outside and there's water in the system it's very easy to freeze ice because of course water freezes at 32 degrees keep in mind that air conditioning and refrigeration equipment is to bring heat and reject heat in and out of the system so whenever you are pulling down yes it is possible for that water temperature to drop but because these systems are made of copper and aluminum they're going to conduct heat in very quickly which is going to help melt that ice even if you have ice in the system you can still remove that ice via sublimation through deep vacuum it can be time-consuming but the best bet there is if you know that you have liquid water in the system use a heat gun in conjunction with a deep vacuum in order to get the best result I do not suggest trying to pool your vacuum slower because again time is money and deep vacuum is the best way to ensure that you do not have those extra molecules in the system resulting in system contamination so deep vacuum is the way to go if you're really concerned you can break the vacuum with nitrogen periodically that's often called a triple evacuation a lot of people misunderstand and think that the nitrogen somehow carries the water it can carry a little bit of moisture through entrainment but in general what you're doing when you see a really good result after breaking with nitrogen is that it's recalibrating the sensor on your micron gauge because the micro engaged sensor was being affected by refrigerant so in a lot of cases where technicians are seeing issues and then they break with nitrogen and then it works properly is more so about the sensor and the micron gauge now working properly and less about actual liquid moisture being the issue I want to finish up by showing the two hose process so if you are gonna pull those two hoses now what we recommend is still connecting the micron gauge at this point you connect it on the side port of the core remover tool either on the liquid line or the suction line whichever you prefer and now you just have to recognize that when you do your isolation test it's almost certainly gonna jump up a little bit as it equalizes because when you're pulling from the same side that the micron gauge is attached to it's being affected by that lower pressure at the pump so once you isolate off those those micron numbers will jump up a little bit which means that when you're using the two hose setup and you're connecting with that micron gauge closer to the pump now you're just gonna have to pull it down a little bit deeper and recognize that as soon as you shut off those ball valves on your core remover tools that pressure is going to jump up just a little bit initially so that is the complete procedure for pulling a proper vacuum recognize that vacuum is good for removing moisture from the system and air from the system the goal is to get all those molecules out so that way the only thing you have in the system is refrigerant in oil which is what the manufacturer ones it's going to result in a much longer life of the system you're gonna have lower fail rates on things like expansion valves and compressors when you follow this procedure to ensure that your system is clean dry and tight thanks again for watching this as I mentioned before go over to the engineering mindset YouTube channel and check out Paul's video specifically about the internal workings of the vacuum pump my video focuses more on the application in the field and his focus is more on specifically how a vacuum pump works so do check that out the links are down below hey thanks for watching [Music]

Channel: HVAC School

Views: 976,018

Keywords: how to evacuate, vacuum pump, refrigeration, evacuation, vrf, air conditioning, hvac, hvac technician, hvacr, hvac school, engineering mindset, hvac training videos, hvac basics, hvac training, technician, rotary compressor, havc, heat pump, hvacr videos, chiller, hvac system, fundamentals, online hvac training, hvac hacks, hvac troubleshooting, hvac tools, compressor, hvac podcast, maintenance, repair, heat exchanger, apprenticeship, hvac design, troubleshooting, rtu, fcu, engineering, Ac

Id: JsnQeUSuUMU

Length: 27min 35sec (1655 seconds)

Published: Tue Oct 01 2019