HVAC 109 Example, charging a low system

so the thick surface medium device inside my returning wet bulb was 70. outdoor dry bulb was 83 so it gives me a target superheat of 23. it's where i want to be at my superheat's actually at 38. i have too much superheated vapor that means there's not enough liquid in there that means i have a starved evaporator high superheat starved evaporator now look at my sub cooling with my same 83 degree outdoor temperature my secondary chart will add a link for some of these that shows that my outdoor temperature should be pretty close to about 10 degrees of sub cooling and i only have 5 degrees of sub cooling so my sub cooled liquid is too low i should be at 10 i'm at five so i have low sub cooling that means i have a starved condensing in it so i don't have enough refrigerant inside i don't have enough refrigerant outside so what we need to do we need to add refrigerant that is we're going to add our yellow hose a scale and a tank of refrigerant so for this we need a refrigerant scale we'll pull our scale out we'll set it as level of a ground as we possibly can turn my scale on and it's showing weight so i'm going to zero this out what do we do is put this over here out of the way next is measure my uh tank referred to me total weight on this tank is 31 pounds of five ounces so it's gonna make a starting point reference here so i'm gonna put somewhere on this tank i'm gonna write 31 pounds five ounces that was my starting point i'm gonna get my third hose ready i'm gonna put it over here where it says the ref refrigerant and since i have the valve this is gonna be a lot easier to do this but i'm gonna take this plug off of here the cap off make sure it has the rubber o-ring and i'm going to put it on my manifold gauge set from there i'm going to take and put this on top of my gauge and i'm going to leave this a little bit loose it's a little bit loose because what's in this hose right now is dirty nasty ugly polluted air and what's in my manifold is also dirty nasty polluted air i'm going to do is open my refrigeration valve that connects this hose to my very center then i'm going to open this i'm going to crack this and i'm going to purge this line the refrigerant from the unit the low pressure side is going to run across the manifold gauge set through the hose it's going to leak out here as it does it's going to push the air out so that's open we're going to open this hear it leaking out the minimus and all i do is just tighten that connection up now that connection's tight i'm going to leave my suction side open but i'm going to close off my refrigerant side and what i'm going to do is open this valve up so now my tank is connected to my center hose now this is a very important step because it's a 400 series refrigerant it is a blend now 410a is the near azeotrope so it's less likely to fractionate but we still want to charge it as a liquid so now this valve is open we're going to turn this tank upside down so now we're getting only liquid out by getting only liquid out we know that it's not going to fractionate now four today is highly unlikely to fractionate anyways but it's so much easier and faster charged with uh liquid regardless so now i'm showing a weight on my scale i'm going to be careful while i hold this because if i move my gauges it's going to move the showing in the tank i'm going to zero my scale out so there's zero weight on there so now i can measure how much refrigerant i'm putting in so now that it's zeroed out i see that my super heat is very high i know that my target superheat is going to be 23 so superheats more important than the fixed orifice so i'm going to add refrigerant until i get my super heat matching my target now because i'm putting liquid in it's going to go into my suction side my low pressure side the vapor gas side i'm putting liquid it'll make sure that that vapor flashes flashes into a gas before it gets to the compressor so we're going to put little shots of refrigerant in just little bitty burst refrigerant to allow that liquid refrigerant to boil to a vapor before it gets to my compressor so now it's coming out of the tank as a liquid and it's going into the line as a saturation and before it gets the compressor ideally it boils or changes state so it's going to give it a little shot as i give it a shot you're going to see these numbers jump up we're going to open this one give it a little shot it's a little shot of refrigerant so i put a little boost in and if you feel the suction line the temperature of the suction line drops because it's flashing changing state from a liquid vapor boiling absorbing heat that's latent heats you can feel the temperature drop so i gave it a little shot i'm going to give another little shot and i'll let the camera see it but right through here we can actually see the refrigerant boil from a liquid to a vapor let's give it a little shot of refrigerant see if we can see it in a sight glass so i'm unable to get it to where you can see the refrigerant to flow but here you can see that our superheat is still very high so we're going to give it another shot of refrigerant just going to open up this valve give a little shot of refrigerant you can see how the pressure changes the high the low side goes jumps up and then it starts to come back down just getting a little shot of refrigerant here can see how the numbers are changing as you can see our sub cooling is starting to climb and our superheat's just barely starting to drop so we can look and see how much we've put in we've already put in one pound five ounces of refrigerant you can see that our suction saturated temperature and here is our actual suction line temperature 78 suction saturated is 45.9 but this superheat that's the number we're really looking at so my sub cooling is now getting within range so we're going to slow down and let it let the refrigerant cycle through and see if it balances out so our superheats dropped to 25 and our sub cooling is still nine so we'll focus more on superior with a fixed surface so let's give it a little bit more refrigerant give it just little bitty shots to allow that liquid to turn into a vapor so we let the system run and at that last charge we have a 20 degree super heat our target was 23 so we've slightly overcharged evaporator coil we wanted a sub cooling of about 10 degrees of sub cooling we have 10 degrees of sub cooling so our sub cooling matches our superheat's pretty close i'm gonna call it close enough slightly overcharged very slightly so we are good i'm gonna call this system good next we got to do is take our gauges off of the system we put in one pound 14 15 ounces of refrigerant in this system so next we're going to take our gauges off right so i'm ready to take the gauges off i'm going to do is turn my tank right side up and i'm going to shut my valve off so with this valve shut completely off i have liquid refrigerant still in this hose i also have liquid refrigerant in this hose as well so what i'm going to do is go ahead and bleed off that last little bit of refrigerant that was in this hose make sure my suction side is still open just going to bleed that across now the refrigerant is out of this hose remember it's already purged now i'm going to take my high side off i'm going to shut my valve off manually two fingers quickly there's also liquid refrigerant in this hose so what i'm going to do is hold this hose up as well as my yellow hose will be up and i'm going to open the high side by opening the high side it's going to bleed the high pressure back to the suction side i'm doing it this way because i've already purged the system so there's no need to switch the hoses like we did before i already have purged the center set so i'm going to open my suction side it's already open this one's open i'm going to open my high side and you can see my high side pressure is dropping and it will only drop to it's only going to drop to what my suction side is so let's drop the other thing i'm gonna do is i'm gonna raise this hose up physically raise this hose up so any liquid refrigerant will drain down shut my high side off i'm going to close this valve take it off my tank i'm going to hold it up so it drains down and then just to make sure i'm also going to hold up my suction hose make sure that liquid goes back into the system now once that's done i'll take shut off my valve for the suction and take it loose and i'm going to go ahead and the minimus now i got the same pressure both i'm going to minimus release that last little bit so my suction is empty i'm going to minimus bleed out that last little bit of it's empty and i'm going to minimize bleed out the last little bit of vapor and it's empty so all three hoses are empty i take my cap i put my cap back on my tank to make sure that stays clean and pure and clear i take my cap from a high side it does not have an o-ring with this style we're going to take and put it on the units same thing with my suction side and so i can put it on the unit put my hoses back where they go i'd never want to let them hit the ground i want to make sure that i don't get any dirty or contaminants in there so screw it back on my gauge manifold set high side on the high side and low side on the low side take my clamps put them back here where they're protected and that's it charging a system with super sub cooling that easy last thing i want to do here i'm going to make a little note and add this to my refrigerant log book i just make my log on my tank i have a refrigerant log book i want to put these in later but for right now i'm going to put one pound lv pound 10 ounces and i'm gonna put the notation of where that was used at i'm going to re-zero my tank tank and the contents is 29 pounds eight ounces so i'm gonna write the new contents on here and i'm gonna add the date on that so that way if i forget to put up my log book i have it right here on the tank itself there's much more that goes to checking the charge this is our introductory basics so we had a system loan refrigerant started evaporator start condenser we added refrigerant until that charge was balanced and that's assuming airflow is good this system does have good airflow it was confirmed you

Channel: Love2HVAC with Ty Branaman

Views: 19,613

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Id: AFoaZEyWctk

Length: 11min 58sec (718 seconds)

Published: Thu Sep 23 2021