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  1. #1
    Join Date
    Jul 2001
    Location
    SW Oklahoma
    Posts
    142
    copeland condensing unit M#FJAL-B200-CFV-001

    Russell Evap coil M#AE26-75B

    Gas is 404a.

    Suction= 32#'s

    Head= 295#'s

    Superheat= 60

    Subcool= 19

    Box temp is 31 degrees, with a 102 degree ambient.


    Expansion valve is new Sporlan BFSE-A-Z

    I have cleaned both coils, pulled the charge and blew everything out with nitrogen, evacuated and recharged. Still can't nail this one. Any ideas??



    Tranetech


  2. #2
    Join Date
    Apr 2004
    Posts
    161
    Had a couple of questions

    Is the entire evap coil active/frosting fairly evenly?

    Is that superheat at evap outlet or total, and is there an heat excahnger on suction line?

    That sporlan expansion valve, is that one of those Bohnamiser valves?

    Can the compressor pull down to 15-20"hg when pumped down?

    Is there a headmaster on system?


    http://www.icecoldcomputing.com/index.php


  3. #3
    Join Date
    Jul 2001
    Location
    SW Oklahoma
    Posts
    142
    The top third of evap is frosting.

    That is superheat at evap outlet.

    Don't know about being a Bohnameiser, don't think so.

    Compressor will pump down.

    No headmaster.

  4. #4
    Join Date
    Jan 2004
    Location
    Earth
    Posts
    4,879
    Is this a new install?

    Is your distributor frosting evenly? If not check to see if a orifice was installed.

    I have even seen russell coils come with distributors clogged with silver.

    Do you have a fan delay on the evap?

    Any P drop from evap to comp?

    Line size?






    [Edited by frozensolid on 06-17-2004 at 06:56 PM]
    A Diamond is just a piece of coal, that made good under pressure!

  5. #5
    Join Date
    Apr 2004
    Posts
    161
    I assuming the freezer did work correctly at one time.

    From what Im hearing, my first thought that new expansion valve is the issue. Sure seems like its starving, w/60deg evap super heat and top 1/3 evap frosting.


    I say this because it looks like #32 psi r404 is boiling at approx 0deg plus normal superheat, i would of expected the evap to start frosting up evenly and suction line starting to frost up too w/box at 31 deg.

    Head press looks low w/that 102 ambient.


    Ive been seeing exp valve kits coming with different refrigerant orifaces, The new Bohn evaps w/Bohnamiser exp valves sometimes come w/3 or 4 different orafaces to be installed before distributor.

    Or, was the exp changed because this freezer was not working with same symtoms?

    I would hope a defrost heater is not on for some reason.

    Well, thats my only guess.

    Im curious what you eventually find out, will you post what it took to correct?

  6. #6
    19 degrees subcooling is means its overcharged. should not be more than 8 or 10. its freezing because expansion valve is pinched off because of the overcharge.

  7. #7
    Join Date
    Nov 2003
    Posts
    501
    I'm thinking about the 60* superheat that Tranetech said that it has at the outlet of the evap. Sounds like the TXV is either sized wrong, or needs adjustment.

  8. #8
    Join Date
    Jul 2000
    Location
    Guayaquil EC
    Posts
    10,460
    You're not going to have a Bohnimiser setup with a standard Copeland CU and a Russell coil.

    The TXV "Z" designation indicates that it's not a MOP pressure limiting valve and there is no mention of a CPR valve on this system. It should have one or the other for proper operation.

    The fact that the coil is not fully frosted would lead me to go with frozensolid and look for crap in the distributor or something along those lines.

    An "overcharge" will not cause the TXV to close off on a system like this, especially with 60 Deg SH.

  9. #9
    i must have missed the 60 degree superheat.
    so high subcooling high superheat = restriction. txv,drier etc..,

  10. #10
    Join Date
    Jul 2001
    Location
    SW Oklahoma
    Posts
    142
    I did change the txv due to these conditions I described, it did lower my superheat a coupla degrees. But the screen was pretty dirty on the original.

    when i pulled it apart, i blew the evap out with nitrogen. Actually, I blew linesets out too.

    I pulled the LL valve, and checked for sticking.

    Installed new LL dryer.

    I've got the new txv wide open, still starving evap. I pulled sensing bulb away from line to see if it would feed more, nadda.

    I've checked and double checked the txv size, I bleieve it is correct.


    The distributor tubes seem to be feeding evenly, so I don't think they are the culprit, but I am beginning to think you guys are right about an orifice problem after the txv.


    This system was installed a bout a month ago, I don't know by who. I am told it has never been right.

    Typical **** sandwich with mayo.................

    THanks guys, it helps to get another persective. I been looking at it too long today, was getting tunnel vision.
    I'll post what I find tomorow.

    And thanks again...

    Tranetech

  11. #11
    Join Date
    Sep 2001
    Location
    East Stroudsburg, PA
    Posts
    13,215

    Hmm

    Capacity issue.

  12. #12
    Join Date
    Jan 2004
    Location
    Earth
    Posts
    4,879
    You probably will think I am crazy, and you may be right.

    You said the valve is wide open. Close it all the way and count how many turns it was from open to close. Reopen the valve forty percent. This does not need to be exact and perfect, just a little less than half.

    Wait an hour and see what happens. Check you superheat, and see what effect this had. I have seen wide open valves do some unusual things.
    A Diamond is just a piece of coal, that made good under pressure!

  13. #13
    Join Date
    Jul 2000
    Location
    Guayaquil EC
    Posts
    10,460

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