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  1. #1
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    Not working in the field

    Majority of systems I work on are on dairy farms. Seldom do these units have an actual receiver and accumulator most have what is called a accumulator/heat exchanger. Recently though I have encountered three different units using receiver and accumulator that were leaking. Weeks beforehand they were topped off until I could fix. Did normal recovery and weighed amounts and were good so I really didn't lose anything during those weeks. Now hears the question, after recharge using subcooling method all my numbers, temperature etc. Looked great except subcooling. I mean I recharged system per manu spec then started her up and let it come to within 5° of set point subcooling was 0? Added 1 more pound because sg was a little snowy and SC was 0. Sg cleared after this pound but SC still 0? I added 2 more pounds then quit because SC wouldn't come up and all my other number were great. I had 10°sh which is plenty of motor protection, evap running at 25, only pulling 20 amps, hp had 30° cond split, TD was 10°. I checked SC on both sides of receiver and same results? Why wouldn't SC increase? All my other systems without liquid receiver SC increases as liquid is added which it should. Maybe I'm being gun shy and should have added more but being 90 plus degrees outside I already had enough refrigerant at this temp plus a smidgen extra.

  2. #2
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    Welcome to refrigeration. Do a search here for subcooling and you will learn quickly that with a receiver, subcooling is what it is. Yes, a single component in the refrigeration circuit throws everything you think you know into chaos. Read, learn, understand. Once you understand what subcooling is and how it is achieved and why it is is necessary, you will see the answers to your questions.
    You have to fight through some bad days to earn the best days of your life.
    You can learn something from EVERYONE.

  3. Likes GoCougs liked this post
  4. #3
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    Yep, reciever makes SC pretty much worthless. You're going to be dealing with superheat, and and a clear sightglass, unless you're using a 400 series refrigerant. Little tip on recievers, run a mapp torch up and down the shell of the reciever, run your hand over the shell from the bottom to the top. Where the shell temp gets hot is your liquid level.

  5. #4
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    Quote Originally Posted by duckman373 View Post
    Yep, reciever makes SC pretty much worthless. You're going to be dealing with superheat, and and a clear sightglass, unless you're using a 400 series refrigerant. Little tip on recievers, run a mapp torch up and down the shell of the reciever, run your hand over the shell from the bottom to the top. Where the shell temp gets hot is your liquid level.
    Thanks duck that's a very good idea it would be just one more way to verify what all the other measurement are telling you. I'm glad I was able to retain my basics and didn't push my systems over. Sound advice thanks.

  6. #5
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    Very rarely have i found leaking receivers.

    See if this helps
    Attached Images Attached Images

  7. #6
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    Relief ports can leak on receivers.

  8. #7
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    Thread Starter
    Quote Originally Posted by duckman373 View Post
    Yep, reciever makes SC pretty much worthless. You're going to be dealing with superheat, and and a clear sightglass, unless you're using a 400 series refrigerant. Little tip on recievers, run a mapp torch up and down the shell of the reciever, run your hand over the shell from the bottom to the top. Where the shell temp gets hot is your liquid level.
    Done some brush up on recievers and read that they should hold 80% of the entire charge. After reading this I thought to myself what if you remove manu receiver and install a larger one and holds the entire charge. Wouldn't this drop head pressure because now cond is empty?

  9. #8
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    Good question. I think the only thing you would accomplish would be increasing the charge.

  10. #9
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    I was thinking that if the volume the receiver could hold increased but charge volume was the same then less refrigerant would stack up in cond which would bring down head pressure because SC with receiver can't be manipulated anyways, just watch SG and SH. I'm just thinking out loud. I have come across some parts and thinking of crafting them together. Kind of like back yard engineering if you understand what I mean. I just completed a solar pool heater using a used 1 hp delaval milk transfer pump. Man can this thing push the water. There's a 2 hp pump there as well that I might install but wife thinks I'll push her around in circles while she's floating on raft. Lol.

  11. #10
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  12. #11
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    If you really want a firm foundation on this topic of refrigeration, get the second edition of this book. It has color illustrations and a CD. As you can see, the Third Edition is most recent, and more expensive. This link shows you the Third Edition Amazon page.

    https://www.amazon.com/Commercial-Re...AEX1PAYDZ4V81Z
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist
    Member, IAEI

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  13. #12
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    Quote Originally Posted by farm tech View Post
    Done some brush up on recievers and read that they should hold 80% of the entire charge. After reading this I thought to myself what if you remove manu receiver and install a larger one and holds the entire charge. Wouldn't this drop head pressure because now cond is empty?
    Are you sure that's correct? I thought it was that, under normal operating conditions, the receiver should be 80% full, which will hold enough refrigerant to flood the condenser and allow the system to operate normally under low ambient conditions.

  14. #13
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    Quote Originally Posted by 71CHOPS View Post
    Are you sure that's correct? I thought it was that, under normal operating conditions, the receiver should be 80% full, which will hold enough refrigerant to flood the condenser and allow the system to operate normally under low ambient conditions.
    Your more than likely correct. Sometimes I read through to quickly and after rereading I find things aren't as exact as I remember.

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