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Thread: walk in freezer

  1. #1
    Join Date
    Jul 2004
    Location
    Texas
    Posts
    6

    Confused

    O.K. Guys, need some help. I inherited a walk in freezer. At one time in mild weather condition I seen this compressor (Copeland AHA2466AXD) completely iced over with the execption of a small ring around the discharge of the compressor. I did add a fan cycling switch in an attempt to get the pressure up and to clear the icing. OK today in the texas heat of 95+,I was running 19# back/225# head. PT chart suggest for this temp the head on R 414 B (hot shot) could be about 177#. As you can see the head may be high on a clean condensor. Suction temp is 23 degrees with 19# being+8, or 15 degrees super heat. liquid line temp is 117 degrees, 225=132 degrees or 15 degrees sub cooling. Even tho the moisture is after the drier I didn't see a temp fall. It is a TEV system, pump down, 4 cycles a day at 30 minutes each, with a defrost termination switch

  2. #2
    Join Date
    May 2004
    Posts
    11,855

    Post lgp

    O.K. Guys, need some help. I inherited a walk in freezer. At one time in mild weather condition I seen this compressor (Copeland AHA2466AXD) completely iced over with the execption of a small ring around the discharge of the compressor. I did add a fan cycling switch in an attempt to get the pressure up and to clear the icing. OK today in the texas heat of 95+,I was running 19# back/225# head. PT chart suggest for this temp the head on R 414 B (hot shot) could be about 177#. As you can see the head may be high on a clean condensor. Suction temp is 23 degrees with 19# being+8, or 15 degrees super heat. liquid line temp is 117 degrees, 225=132 degrees or 15 degrees sub cooling. Even tho the moisture is after the drier I didn't see a temp fall. It is a TEV system, pump down, 4 cycles a day at 30 minutes each, with a defrost termination switch


    I don't understand what you mean by moisture is after the drier. Do you mean moisture indicator/sight glass?




    First of all your compressor is a Tecumseh. AHA2466AXD

    R-12, low temp -10*, 4660 BTU

    http://www.tpc-nacg.com/mdlnmbr1.htm

    Your suction pressure is too high. With your pressures and temp that you show, you are overcharged and/or you need to adjust your TXV. Simular situation from a previous post below.


    With HotShot you can forget about clearing your sight glass or you will have an overcharged condition. HotShot is 50% R-22, that is why you will run high head pressures. 180* to 225* are not that unusual depending on your condenser location ambient. HotShot needs good condenser air flow in a wide open area. You may want to consider converting to R-416 if you are in a closed air space.

    If your condenser coil is clean and you have correct fan blade/motor combination turning in the proper direction then there will not be a problem with your condenser coil.

    Here is what I would do assuming you are EPA certified and experienced with such things.


    Make sure the condenser coil is clean and check the blade direction.
    Check your subcooling at the liquid line out of the condenser coil. (around +10* + - a few)
    Check your superheat at the TXV bulb. (around 8* to 12* for medium temp and 5* to 8* for low temp)
    Adjust your charge for subcooling first then superheat when the box gets close to cycle temp.


    If you have added HotShot to your system to clear the sight glass, my bet it is overcharged. Check the above first, and then make your adjustments. I am sure you will find the box will run efficiently. If not please get back with us.


    Please read the following for more of an understanding of subcooling and superheat.
    http://hvac-talk.com/vbb/showthread.php?threadid=54493





  3. #3
    Join Date
    Jul 2001
    Location
    Gold Coast of Connecticut
    Posts
    4,543
    what was the condenser air entering temp, maybe have to sell a bigger condensing unit to the guy , this must be one small box?

  4. #4
    Join Date
    Jul 2004
    Location
    Texas
    Posts
    6

    Walk in freezer

    Yes I am epa certified, however most of my back ground is in A/C. and yes I meant it to be moisture indicator, (sorry) And I forgot to include that when I first seen this and the compr. was all frosted over the box temp. was running -10. Now about the best I can do is +10 to 12, not so good. The info I gave earlier was at +18. The air in was 95+ ,condensor Hotshot was not my choose, some refrigeration co changed compr and put it in

  5. #5
    Join Date
    May 2004
    Posts
    11,855

    lgp

    I understand what you are saying, thanks

    When you found the compressor frozen over or converted to "frosty-the-snowman" what you had at that time was flood back to the compressor. It can be caused by several things.

    • Thermostat bad or sticking closed or 100% run -(doubtful)

      Moist air infiltrating the box that caused coil icing which in turn could not transfer heat from the box

      A defrost problem in the coil such as bad heater, heater pulled away from the coil or even scorched contacts on your defrost time clock

      Bad or out of adjustment TXV

      Overcharged box, this is easy to do with HotShot as it is only 80% charge of R-12 and you don't clear your sight glass.

      And a few more things that you may want to look for but not right now.


    Here is something else you may want to think about. If this compressor has seen its share of flood back there could be valve damage. If this is the case you have lost capacity and you will never get this box down. You may want to pump this system down as far as you can. If it pulls a vacuum, great, if not, you may have bad valves. Let it sit for a while and see if your suction pressure rises and tries to equalize. If you have a good tight liquid solenoid valve and you shouldn’t equalize.

    My first post is still my bet. It is either overcharged or the TXV is out of adjustment with your temp and pressures where you say.

    Good luck and keep us updated





  6. #6
    Join Date
    Jul 2004
    Location
    Texas
    Posts
    6

    Walk in freezer

    Luster, thanks for some good info, yesterday I did do a capacity test on the compressor, by closing LL service and it did pump down and shut off, it rose to about 10# and held, don"t suspect a compressor problem do we. As I said earlier I am an old A/C guy . Refrigeration is a whole new world, Right. With you guys help I know we will get this thing arrested. With the compressor I mentioned, what TEV would I replace it with? All that I have on it is its R12, W a number like BFFEAZP, does that tell you any thing? Thanks from cowtown

  7. #7
    Join Date
    May 2004
    Posts
    11,855

    lgp

    You have a Sporlan BFFEAZP. This valve is Flare,R-12,External equalized and low temp. The valve is rated from 1/2 to 1 ton. I don't think you need to replace it just adjust it.

    http://www.sporlan.com/Prodinfo.shtm

    You can download chart #10-135 to help you with adjusting your valve.

    If you pulled a capacity test on the compressor and sure your valves are in good shape. Simply adjust the TXV to lower the superheat. Look for somewhere in the 5* to 8* range. Your 15* is way too high.


  8. #8
    Join Date
    Jul 2001
    Location
    Gold Coast of Connecticut
    Posts
    4,543
    Just because it pumps down does not mean it is a good compressor. It should pull 20hg if it is really good. Also one piston could be completely not working either a rod broken or a suction reed problem and it will still pull 20 hg.

  9. #9

    Screw this suction service valve test!

    I mean ... turn that screw all the way out and remove your gages and get off that system and go get yourself the compressor curve data and THEN you can test the compressor to see if it has a capacity problem.

    If hot shot is in the sealed system you probably want to change it out and put something else in there which is more appropriate.


    (screw in the valve .... yeh right)

    Ya know, I make my share of dumb moves.

    I have made MORE than my fair share of mistakes.
    But once someone introduces me to the better way of doing something .... I dont ever want to resort to my old ways again! Period.

    If nobody knows about compressor curves, visit copeland's site and join in.
    Aside from using the data from copeland, we would all be called hacks. And rightly so. ause we would be flying by the seat of our pants.


    I have nothing to be proud of. I have nothing to toot my own horn over.
    God made me smart enough to be able to see, watch what other people do and to listen to what's told me.
    And He gave me reason. Or common sence.

    Once, only once, I replaced a unit which didnt need changing. And I did so AFTER I screwed in that suction service valve! And ya know what?
    That particular compressor didnt pass the stupid test!!!
    Yea, that's right! I called it a stupid test!!! Cause that is what it is!

    Because of guys like me, they came out with curve charts! Because of guys like me, there are guys like me here on this forum telling people to NOT use that stupid test!
    To be ignorant is one thing. But to be ignoring knowledge is another.
    A smart man can be ignorant on certain information. But once he is informed, he is all the more smarter for it. Cause he listens and learns and applies what he has learned. He comes out a winner.

  10. #10
    Join Date
    May 2004
    Posts
    11,855

    enough said...

    Here is something else you may want to think about. If this compressor has seen its share of flood back there could be valve damage. If this is the case you have lost capacity and you will never get this box down. You may want to pump this system down as far as you can. If it pulls a vacuum, great, if not, you may have bad valves. Let it sit for a while and see if your suction pressure rises and tries to equalize. If you have a good tight liquid solenoid valve and you shouldn’t equalize.

    My first post is still my bet. It is either overcharged or the TXV is out of adjustment with your temp and pressures where you say

    If you pulled a capacity test on the compressor and sure your valves are in good shape. Simply adjust the TXV to lower the superheat. Look for somewhere in the 5* to 8* range. Your 15* is way too high.

    It doesn't take a PHD in DUHHH to figure out if this Tecumseh Compressor has valve damage. If lgp follows his subcooling and superheat readings and is not able to get it right with the info provided he will know if this 4660 BTU compressor is pumping properly or not.

    Thanks for your help guys.

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