indeed, all blends MUST be added as a liquid. for the very reason you stated.
Hi all,
I have been getting some mixed signals lately from the mechanics in my shop on charging a system with 404A. Please feel free to correct me if I'm wrong but when you go to weigh in your charge on a 404 system are you supposed to charge liquid or vapor? I have asked a few people in my shop but I'm getting mixed answers from them which makes me wonder if some people know what there doing? My understanding is that 404A is a blended refrigerant and needs to be charged as a liquid due to the glide factor of one refrigerant compared to another. If you charge as a vapor will you not fractionate the refrigerant? Please feel free to drop any tips on what the best practices are when working with this refrigerant.
FYI-the type of coolers I'm working on are holding between 50-80 oz of refrigerant and holding temps of 34-40 F
indeed, all blends MUST be added as a liquid. for the very reason you stated.
All 400 series refrigerants are blends. That means they are made of of different refrigerants and they will have different boiling points. When you vapor charge you are boiling the refrigerant off inside the drum because of the different boiling points they will boil off disproportionately. This is called fractionation.
What that means is....yes you should liquid charge only with all 400 series blends except R-410. 410 has such a close glide the fractionation is negligible.
That is the fastest response i have ever got regarding a question. I wish the mechanics in my shop where that quick. THANK YOU! You guys rock!
I agree with all the above.
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So then let me pick your brains for a minute to see if my practices are right.
I find a system low on gas, i recover, pressure test, find and repair the leak, pull the vacuum to 500 mic (if possible), then when the system is under vacuum i charge it by using the vacuum. what ever doesn't make it into the system i then run it and start adding the "liquid refrigerant" to the suction side being careful not the allow it to spill in too quickly, all the time watching the sight glass on my gauges to make sure the refrigerant is bubbling/ vaporizing in the manifold since i could freeze the valves if i dump it in too quickly. the whole time i am watching my scale making sure the appropriate charge is applied.
Please feel free to give me any suggestions.
I think you got it.
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u got it.. ill just add one thing cause i no someone else will.. Watch the amperage of ur compressor as ur charging also
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Not to sound like to much like an apprentice but am I watching the amperage for an increase or decrease. I'm guessing an increase due to the fact that the compressor will work harder once it is fully charged or if I'm letting in the liquid refrigerant too quickly? Please do elaborate.
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One more thing PAPMG get your post count up and apply for pro membership
lot's of good stuff here and more soon to come.
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Thank you so much for all of the information you guys. It can be really frustrating out there sometimes and there are some days you just want to pull your hair out while on a job because you just can't understand what's going on.I got into the trade a little later in life and i think it helped me understand what doing this work really means. One thing that I do realize, is that in this line of work there is no substitute for experience and you only get the experience by putting in the time. i was fortunate when i first started off that i made friends with some much more experienced mechanics who took me in underneath their wings and taught me the basics from the ground up like how to properly hold a ladder and so on. I've since moved on but still keep in touch with them and have learned so much on my own but do wish i had that mechanic there sometimes to ask that question. The shop i work in is alright place because they let you get your feet wet in just about everything but the downside is your always left to fend for yourself. I guess it's not all bad. how else do you learn.
Again thanks for all the info and the help. i will definitely get my posts up and apply for the pro membership. Hope to be talking with you guys again soon. "Much Respect to you guys" PAPMG
Where did this guy come from? If you ever move to Phoenix, and need a job, give me a ring. An apprentice with a brain, a dying breed.
LOL. Your right.
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404a has to be charged as a liquid no exception.
Had the oppurtunity lately to work on 2 identical upright True freezers, both needed refrig. work and recharge.
Out of curiousity.. What I'll call system A was charged liquid 404a only.
System B was charged gas only from vacuum to full weighed in charge.
Both units were charged simultaniously side by side then started at the same time after fully charged,allowed to equalize and at the same internal temp.
"A" took exactly 1.5minutes less to reach temp. and shut off (both t stats set at #4) and pressures were only 2 to 3 psi lower onsuction and about 4 psi lower on discharge.
Now could the cycle time be attributed to variances between the mechanical thermostats???
As far as pressures... you be the judge.
I charge by liquid from vacuum till it takes no more then start unit and gas till fully charged on self contained units less than 1 lbs and liquid all the way on walkins. I guess I'm afraid of damaging the compressor.
Yes I know not a good practice but I never did lead by example anyway
I've never had any problems with this practice yet, but for new tech.s I do agree with liquid charging only. Develop good practices right from the start and use the scale to charge factory weight (when available).
I mostly charge by feel, and have tested my "feel charging" by recovering and weighing my charge and comparing to factory and am seldom more than 1/2 oz. off.
I guess it's because I was taught "old school" on alot of remoted cap. tube systems.
Ok go ahead chastize me
I have a question as a new member. i have worked on the premise as an old school tech ( R 11, 12 ,22, ) who has been out of the loop for several years that you could charge a system by adding 30 to 35 degrees to you ambient around the condenser and that would be close to an accurate charge. will that work with blends ?
I had the same problem when I started out and thought every refrigerant should have a general operating range. Truth is there are a lot of variables and it would be better to work on using the correct principal's. Sub cooling and super heat are your best friends. I would take more stock in the temperature of the refrigerant than the pressures, but becarefull not to totally disregard pressures.
it says right on the dagone box it comes in ..... charge as liquid