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  1. #1
    Join Date
    Mar 2006
    Location
    louisville ky
    Posts
    5

    Hmm

    FHP model EMO048-3HZC serial DAO97215. Original call was continous blower fan, the cause was stat never would satisfy in heating mode. This is a water source heat pump. My loop temperature is 77 degrees F, clean strainer and 12 gpm flow. Charge was removed and weighed back in. Metering device is cap tube. 70 degree indoor temp, low load. Blower speed low. Cleaned evaporator and checked blower rotation. Cooling mode pressures 75/250, 0 superheat and 18 subcooling, 20 degree delta across evap. Heating mode pressures 36/175. Now here's the kicker 50 degrees superheat?? Reversing valve appears to be shifting properly. In heat mode refrigerant cap tubes frosting back to condenser loop? In order to bring heat on until I can resolve this problem I blocked about 2/3 of evaporator coil. Cap tubes are suspect but why the difference in superheat from heat to cool? Any help greatly appreciated.

  2. #2
    Join Date
    Dec 2005
    Posts
    1,923
    more than likely your evaporator coil is full of oil in its lower tube. Thus, when you run in heat mode, the oil cannot pass through the cap tube with such low delta pressure.

    Run the system in cool mode at highest blower speed (note that you have 0 degrees superheat in cool mode) and get some heat load on the system (flood light or something). Hoping that the oil gets back to the compressor, then run heat mode.

    Good luck

  3. #3
    Join Date
    Dec 2005
    Posts
    1,923
    The data you have there is not good either.

    Water cool system with water temp @ 77 degrees and you have 250 PSIG. Also your evaporator pressure at 75 psig, which mean 42 degrees coil. With such low load and you have 20 degrees delta

  4. #4
    Join Date
    Sep 2004
    Location
    Kansas City, Kansas, United States
    Posts
    13,833
    Hmmmmmmm low superheat high subcooling high head and high suction even for an average load. Is your amp draw too high? Discharge superheat high?
    maybe you should check your SCALE!
    LOL Frank


  5. #5
    Join Date
    Oct 2003
    Location
    tidewater, va
    Posts
    2,147
    blewbyou

    I think that the answer to your problem can be found with the answer to an important question. What is the temperature difference between the wate in and water out in both modes. You know you have the right charge. That is square one. Oil logging...very unlikely in a close coupled unit. Lets go back to basics and forget the exotic stuff for now. No knock on just opininion, but if you are scaled waterside and you can't get rid of heat in AC, you get a high head. I think your head is a little high. So, you have proven FLOW but how about transfer? A low temp rise in ac on the waterside with proven flow says scale. Now, in heat you look at a low back pressure. What I can't explain is high superheat and then 0 superheat. That being said, (A) verify measurements and (B) lets get temp splits on the waterside. Good luck.


    r404a

  6. #6
    Join Date
    Dec 2005
    Posts
    1,923
    If your water loop is scaled up, then you will not have high sub-cool. Don't you agree R404.

    Also his post states that the cap tube is frosting right after the condenser in heat mode. This tell us there is something ristricting. I don't think there is drier (unless someone add a drier). Thus, there is oil in that condenser coil since it runs such low superheat in cool mode for long time and the oil is migrated in the coil.

    It is just dicussion. So none taken there R404. We are only trying to educate ourselves.

  7. #7
    Join Date
    Oct 2003
    Location
    tidewater, va
    Posts
    2,147
    just opinion,

    you are right, high subcool probably wouldn't be seen on a scaled HX, but I have a hard time with flooding one way and starving the other way. Someting doesn't jive. That said, water splits HAVE to be taken on watersource so we get the full picture. Also, if he pulled the gas again, it wouldn't hurt to cut the air coil outlet and blow it ou. That would be to check for oil. I still think that would be a stretch, but, maybe if this thing had a few compressors in it, it is possible.


    r404a

  8. #8
    Join Date
    Oct 2006
    Posts
    34

    blewbyou

    just a stab, but did you change the drier? made sure to use a bi-flow? i just installed a drier backwards yesterday, but caught it before i added the gas good luck

  9. #9
    Join Date
    Jun 2004
    Location
    BR,LA
    Posts
    256

  10. #10
    Join Date
    Oct 2006
    Location
    Emerald Coast, FL 30.1N 85.8W
    Posts
    681
    On a cap tube, high superheats are normal if the evaporator is seeing high latent & sensible heat loads.

    Another reason causing high superheat is that your suction pressure and temp is lower than normal, which starves the evaporator -- this cries out low charge.

  11. #11
    Join Date
    Oct 2003
    Location
    tidewater, va
    Posts
    2,147
    The man said he pulled and weighed in the charge. This is a crucial step in proper operation and troubleshooting. I can't see how , if we have the same metering device being used in both modes, a cap tube, that we can have a restriction. I am really curious to learn what is found on this one.

    r404a

  12. #12
    Join Date
    Dec 2005
    Posts
    1,923
    emcoasthvacr,

    The system is not low on charge because it has 0 degree superheat on cool mode

  13. #13
    Join Date
    Jun 2004
    Location
    BR,LA
    Posts
    256
    ?1 77* loop is that temp the supply or return

    ?2 how did you verify 12 gpm

    ?3 what is the chances of the original charge having air in it. was the original charge put back in



    [Edited by joeywpittman on 11-06-2006 at 06:37 PM]

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