HVAC Training What is HVAC Part 3

my issue with 20 degrees is it's the top end i'll ever let system be my personal opinion as to why somebody like copeland recommends that is one they've designed to that right so they factor that in scroll compressor for example when we really get down to the details isn't going to start truly overheating or having heat issues until you break 30 degrees but you're losing lot of efficiency out of that system now most people lot of technicians over the years at least don't understand these systems well enough to balance them in the way that we do many times and so where our target most of the time is 10 to 12 degrees maybe 15 on the top end on majority of our systems and if we don't see less than 15 lot of times we're not very happy and that comes down to purely efficiency and don't recommend on standard system going below eight never have target for eight but if i'm running 8.59 degrees i'm not going to fret about it either as long as know that system is maintaining now can tell you lot of the older semi-hermetic compressors you got you got above 20 degrees you would start having serious heat issues copeland yeah carlisle there we go carlyle 06es 06ds they did not like those superheats yeah you run 25 30 degrees on one of those you're gonna tear the valves up in it and you're gonna walk up to it and you're gonna see the heads all cooked and crusted because you're running too high superheat it needs that additional cooling as long as you're between 10 to 20 you're okay if i'm intentionally trying to tune or balance the system i'm going to target that 10 to 12 range if can hit that 10 and 12 am perfectly happy because what's interesting is we just did system it was was it 12 or 15. it's 15. they recommended 15 by the manufacturer but again you go back to copeland's scroll which is what these were recommendations they don't want you to go below 20. but the manufacturer told you to go to 15. so who's right who's wrong it's lot of safe zone to where if you set it up for that in the way that they intentionally designed their compressors it's not going to it's going to be lot harder to get low because that compressor will live whole lot longer running warm or hot then it's going to run running too cold and what mean by too cold is it trying to suck in liquid it ain't going to run very long that way so they have to create parameters and recommendations for lack of technician training and lack of your understanding good sub cool what about sub cool 8 to 12 under what conditions the most perfect answer is what is their comfort level are they comfortable at 70 with 50 humidity are they comfortable at 75 with 50 humidity so what is their comfort level the reason i'm taking it to that comes back to the load itself because again if you're trying to charge this system after it got warm or say you're walking up to it and it's it's been down for day or two it had it had contactor failure you replace the contactor you turn it on it's 80 degrees in the space but they want it to be 72. you crank it up and you're running you should be running 15 degree split on your condenser saturation but instead you're running 20 degrees and instead of having 12 degree sub cooling you push in 15 to 18 degrees of sub cooling well that starts raising questions or it should why am running this high do you know the answer you got heavy load that's all it is because you can make that system operate at the readings you want sub cool and saturation on the condenser if you were to set it up to run at 80 degree indoor so you have to be careful with those two numbers they're completely variable on the indoor load conditions and you have to think about that anytime you're looking at that charge the super heat should be consistent the this evaporator saturation will be fairly consistent you need to be within few degrees for the final readings but that sub cooling is going to completely depend on what that evaporator is doing because it could very easily look over under charged real fast depending on how far away from what they're asking it to do and most technicians never even think about this they fill it up slap it up run on so if they were charging the system at that high load it's going to look maybe slightly under charged by the time it gets down to their set point now don't know that it would go to that extreme but it's possible mean yeah if it's in that poor condition as whole it's possible it could freeze normally you just you're going to be if you had 10 degrees at that 80 you might only have four or five by the time you get down to 72 of sub cooling and so now you're creating scenario where the system has hard time maintaining on hot ambient day because they charged based off of high ambi or high indoor load so be careful using sub cooling it is 1 000 necessary and needed but be careful how you use it push pull recovery we actually had scenario today where this could have helped the on-site tech if we had to practice this and this is something that especially dealing with high pressure refrigerants for 10a prime example you even though you're not having to move lot of weight it gets so bright and hot on the roof this might help you in your recovery in this particular case we didn't have any water available we only had 12 pounds to move but in matter of hours because the tank would get so hot and it would build pressure we could only move barely seven or little over seven pounds in in an afternoon so we've got our condenser and we have our line set going out wherever it goes doesn't matter say this is your liquid line and suction line this obviously is split system it doesn't matter if this is rtu split whatever design setup it is when you do recovery like this you want to hook the suction port of your recovery machine to the liquid line so we're going to pull off of the liquid line come into our recovery coming this way then we're going to go oop nope damn it chris know you're watching recovery tank is what meant to say going into the recovery tank on the liquid port okay you're going to come out of the liquid line into the tank on the liquid port then on the vapor port you will come back out into your suction of the recovery machine yeah this is our rem recovery machine then we're going to go back out to the discharge port we're going to come right back over to the suction this is push-pull method what is happening here is we're drawing the vapor off the top of the recovery cylinder and don't trust the colors because the colors will fool you just had tank last week no it was the blue was liquid and it said it and the red was one the other day gas it was they were different colors and they both said what went on somebody had fun with that one anyway we're so the the goal is the where you're gonna generate the most heat is during the liquid phase of this recovery so what we're trying to accomplish is we want to draw all the liquid into this tank but not build pressure on it so we're pulling the vapor back off the top of the tank into this the recovery machine and pushing it back into the system and what that'll do is that helps push this vapor that has gone through this the recovery system will help push that liquid back to this liquid point and what you will do is you'll be able to draw all the liquid out which so say we had 10 pound system probably seven seven to eight pounds of the recharge in that system is liquid the other two to three pounds is the vapor if you practice this you won't generate the heat in your tank and it won't get hot and build so much pressure on you it'll maintain that neutral temperature or whatever ambient is around it if you've got the sun blasting it obviously that sun's going to heat the metal up but the point is if you can keep this in the shade you can keep this at ambient eventually once you get all the liquid out of it which you can tell by watching the scale so that scale once it's going to be rapidly inclining while the liquid phase of that recovery is happening when you get to the point where that scale begins to crawl or basically stop you're down to just pure vapor at that point because all you're doing is you're just moving vapor through you're not actually adding any more refrigerant directly to the can so when that scale just halts you're there and then you would set up like normal recovery and just pull the rest of the vapor instead of trying to pull all 10 pounds or push all 10 pounds into this can and generate all that heat of compression you moved seven pounds into this can and generated no heat of compression because there's no compression there and then your then you're able to just recover the little bit of vapor that's left it's great for 410a because it has so much pressure your g5 twin recoveries are going to trip out at 400 psi which for 14a doesn't take long to get there the initial complaint and then you need to ask for your readings and what you want ac is not cooling what do you need to know so you walk in you hear the the blower running you got air out the vent you walk outside and condenser fan motor is spinning compressor is running and the the liquid line is very warm to the touch so what else do you need to know keep in mind these are well on everybody what what do you need to know you're going to hook up gauges and all these scenarios by the way okay i'm going to pause there why do pressures matter they correlate because of what all right pt chart other than knowing what refrigerant it is should pressures matter anywhere beyond that what matters more the pressure or the temperature it represents the temperature my point is mean it wouldn't matter what refrigerant you were dealing with you walked up and it's hot you're under high pressure temperature is the temperature is the temperature the refrigerant r12 410a 22 134 don't mean anything the pressure is only tool to get you to the temperature so don't worry about the pressure focus on the temperature so in these scenarios i'm not going to give you refrigerant because it doesn't matter it works the same all right let's see we got so you wanted what what do you want what readings do you want temperatures what temperatures all right set temps all right so your condenser sat is 80 and your evap sat that's not what should have wrote there you go is 20 degrees what's our outdoor air outdoor air was 80. 18 80 degrees you should shouldn't you you're charged under pressure do you know or are you guessing well at this point just those numbers i'm guessing okay all right point your direction okay that's good you're not diagnosing you're trying to figure it out that's the point i'm making is we don't guess we need to know so what do you need next all right team guy at that point your liquid line is 80 sub cool zero suction line whatever we're doing seventy super heat is fifty you're on charge my immediate my immediate looking at that looks undercharged said did say that right didn't say that right technically said that backwards said that right super 850 20 degrees yeah what am saying anyway under charge why why is it under charge well you got low potential fat because we've got low pressures which aren't important you know but you have low condenser sac you have low evap side you have high sub or low sun pool high superior you know so cool as you mean as you add refrigerant to that system that cell pool is going to come up that superheat's going to come down to our desired range and as you add refrigerant you're going to bring that condenser side up it's just all about balancing numbers right everybody agree anybody see anything different anybody want to know anything more information is this trick question does everybody agree let's run through the scenarios how do you know what it's not this should be part of what you do mentally as part of your troubleshooting process so you believe it is low charge all right airflow how do you know it's not airflow because if you increase if you were to increase airflow you're just going to increase the superheat right so increase airflow increase superheat but if you decrease airflow that's right you decrease airflow you decrease saturation so you lower your superheat maybe sure but you also lower your saturation which is too low right okay we ruled out airflow not that how do you know it's not the metering device because again it's it's about how well this evaporator evaporator's picking up heat right so why couldn't it be the metering device because if the metering device was over feeding you would have higher evap sag right over feed higher sat and saturation increases and what else changes they're clean focus less on that what's going to happen to your superheat it's going to drop right you're going to do more than drop you're going to flood so we definitely don't have flooding condition is the point so we know it's not an over feeding valve what about under feeding valve how do we know it's not just not feeding enough what would you see different if it was under feeding txv wouldn't have any superheat wouldn't think because it's all going to be gas as it goes through well no you would have super juice because it's kind of cool there you go you're what would be different well if you were under feeding you're going to lose evaps right right so which is what we have evaps at dropped super heat's high why can't it be bad txv because your your condenser side would say it's too low feel like okay device is causing the restriction so what's going to bring up your sat temp on your condenser side yeah you're on point yes saturation while it may not run high it's going to be higher you're not going to run neutral saturation and typically your liquid line will run right at saturation i'm sorry ambient temperature because again we don't have lot of load on the evaporator so there's not much load but even without the load because we this this is our indicator of our of our load coming back we don't have much load but we have elevated condenser saturation and our liquid line is running lot of times neutral to ambient temperature so no you would have sub cool at that point the point is though you can rule out that those are not the readings you would get with an under-feeding valve because the condenser readings aren't where they should be we've traced that far enough the answer is you are correct this is undercharged system my point behind that exercise was why is it not the other things and we have to work through that process why is it not this stuff what time what's our time we can work through at least one more all right this complaint is air conditioner runs but it is it's not comfortable it's not keeping up it never shuts off never shuts off it's uncomfortable what do you need to know okay so we have thirty and one hundred you have 90 and what did say yeah yeah 10 don't know what i'm thinking there and 25. yeah didn't even we'll get into glide next class okay these are your readings outdoor outdoor what 90. so if you're not sure what it is start ruling out what it's not well it's not undercharged not undercharged why is it not undercharged so cool super he looked good well yeah evaps that's little lower than wanted my outdoor my condenser sets little lower than wanted to flow so condenser sets low evaps that's low you're happy with sub cool you're happy with super heat indoor temperature return air is 78 and supply error is 65. okay right no low ambient not under loaded so we've got we've got load where we need load good line okay so your metering let's device mean you said last time that and when you have an under feeding metering device that your outdoor air your liquid line are gonna pretty much flatten down so why is is it is it too much airflow we have too much air no no why is it no that's right evap saturation is low is it not enough air flow saturation's low so that's right low superheat so superheats high by our standards saturation is low so it's not high or low airflow it's something outside of that we've eliminated air flow wouldn't say it's under charge because if you charge it up more you're so cool it's gonna come up yep and your superheat's going to go down which we want the super each go down but we don't want whole lot more stealth yep so based off of the sub cool and the load we know that it's probably not charge issue it's very not not likely so what else okay it's metering device so what are we dealing with what's what's wrong with metering too device okay didn't include that 78 let's say we got 45 rh 45 rh good question by the way yeah sorry guys it wasn't fantastic in the chat it's all good overfeeding is going to give us yeah so so over feed yep evap sat goes up and what else superheat goes down that's right we have the opposite of that why well would say under feeding it's had temps low superheats high because it's pulling it's it's all vapors and we've eliminated airflow we've eliminated charge that leaves us with metering device we know it's not over feed it is an under feed valve it's not feeding properly it's not dramatic but it's not working right either all right let's see if you can figure this next one out this next one's this next one's going to be bit more challenging all right so we got 75 we've got 55 supply we've got see 140. 120 this would be 20 degrees ambience is 100 and we have 45 sat 55 liquid line in 10 degree superheat suction line sorry 10 degrees 55 suction line and 10 degree superheat all right now the complaint it's uncomfortable system runs for long period of time we hear funny noises outside okay because we have high condenser set we have high evaps hat we have high so cool and low superheat as you increase charge your sub cool comes up your superheat comes down generally evap chat's too high condenser sets too high we should be looking at like right about what 15 to 25 above outdoor air most systems today you're talking 15 degree on the condenser 15 is this is this standard maybe 20. yeah yeah not most of the systems that ran 30 plus aren't around anymore except for something yeah so you're thinking overcharge dig too far into it but i'm looking at high condenser set high evaps at high cell coolant low superheat the superheat's not really low the superheat is where we want it mean it's closed you got 20 degree split okay okay you're correct in the fact that this can very much look like an overcharge so what we'll do let's say you removed some charge or say you're completely recovered and we went back with factory charge all right or actually yeah you go back with factory charge in this particular case you get the same readings even after confirming factory charge that's what it would be sorry you'd take drop across the dryer dryer drop is one degree so not dryer and you're at factory charged fan speed because we our superheat would be high would be increasing load if we had too much fan speed right yes yes so yes we do have high set well is 45 high yeah would say 45 is acceptable i'm fine with 45. again most coils are actually designed to run at 45 this one is outside of the box it'd be it'd be 40 degrees across the condenser outside so it's 140 yeah be 40 degrees again this is standard system by today's standards so you're hero i'm sorry couldn't resist it this is standard system with 15 degree target condenser split you're under high load are you under high load 100 degrees outside you got 100 degrees 75 return that's decent load on both sides of the coil you've got load wouldn't call it high load but you have load definitely don't have too little but with high level the higher load you should expect little bit high condensers that little bit higher little bit higher i'm going to give one extra clue the there was another technician here last week worked on it and don't remember what he did but it was something with the outdoor unit and it's only kind of worked since then it's still not comfortable our set point our set point is seventy-three fan who said that of course no it is not it's spinning in the wrong direction so you're introducing heat to your coil somebody replaced the capacitor and mistakenly reversed the start and run reversed direction on the fan motor that's the thing when you're walking up to call this happens it may not be very often but it happens and sometimes it's easy to switch two legs because you're just in hurry you got five more calls to get to you you just you're trying to get through here and get gone right and then this callback comes through or maybe it was after pm and there was an apprentice who just didn't know any better he hadn't done that yet because all of us do it eventually and this these are the conditions you're going to see and you would think it'd be obvious the condenser fan's not spinning the right way but can tell you my personal self the first couple of times ran into this actually remember the first time ever saw it blew my freaking mind could not make sense it looked overcharged i'd pull charge out it wouldn't correct it was constantly high could not get the high side to stabilize and it would run run run and eventually trip out on high head and shut down and then reset and trip out and reset and you know it was going through this vicious cycle at the condenser and eventually just was standing there with my hand on it and it slaps you like freight train why don't feel air what mean the fan spinning why in the hell do not feel air well you get down looking you realize yeah it's spinning backwards or even if it's not capacitor maybe somebody maybe the last technician he didn't change the capacitor he changed the fan motor and he forgot to switch the rotation legs because he wasn't thinking about it again he's in hurry it's very easy mistake to make at any level don't care what your experience is and if you're not paying attention it'll it'll rock your day anyway good job online next month we're going to dive deeper we're going to go more of the advanced side of the refrigeration cycle and get more advanced with how we do controls and eevs and hot gas bypass and balancing and reheat coils and all of the advanced side of it this class here was intended to be entry-level refresher of just the fundamentals of what this industry does and what we do and why so just keep in mind that'll be next month and we'll go from there appreciate it everybody