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Thread: Rtaa retrofit

  1. #14
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    Apr 2012
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    FYI 407c evaporator glide is generally said to be 8 degrees F.

    The bubble and dew are 11 degrees apart at a normal evaporator pressure. Flash loss will never allow the bubble temperature to be reached in an evaporator.

    Average evaporator temperature will be four degrees less than the dew.

    Im not sure how many orings are in the system but as mentioned in a post above, they will need to be changed.

    Also, I normally start with 90 percent r-22 nameplate charge and adjust as needed.

  2. #15
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    Since R22 is so expensive now, what does everyone think now about converting the RTAA?

  3. #16
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    This is an old thread, but is now more relevant than ever. At this point, I still haven't tried a retrofit, but I can see it in the near future. I still haven't heard of anyone else trying it either. Maybe someone will chime in with some experience.


    Have wrench-Will travel

  4. #17
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    RTAA EXV is controlled by the difference of the two temperature sensors mounted on EXV expansion side and suction. There´s no pressure reading, so it will be no problem controlling it with R407C. But one thing I tell you, you´ll have to get the next size of EXV, or try to open the orifice...

  5. #18
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    Quote Originally Posted by DigtalCracHead View Post
    Since R22 is so expensive now, what does everyone think now about converting the RTAA?
    i think the same as i did before. not a good idea. fix the leaks and leave it alone. in every case i found (theoretically), R407c costs you more in energy costs. R22 is a fixed, one time cost. the energy used is EVERY time the compressor runs. add in a small leak and with R407c you are most likely recovering and replacing all of the refrigerant (fractionation). with R22...top it off. that is cheaper, too.
    Someday, I hope to be just as brave as Harry Stamper.

  6. Likes stanbyyourword liked this post
  7. #19
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  8. #20
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    Dec 2013
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    1. Remove all the automation of Trane.
    2. Install the new controller, allowing screw compressor control in the continuously variable mode. It will be easier and cheaper than to invent a bicycle with square wheels.
    3. Set more powerful fans (condensers power decreases by 12% at the transition 407)
    4. Oil, sensors, all for a replacement.
    5. Wash all the old oil from the evaporator.
    6. Forget it and buy a beer.

  9. #21
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    Jul 2007
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    Trane doesn't have an official retrofit solution in the States and I've never tried it but there is a set point in the bottom of the configuration menu to select the refrigerant in the machine. The choices are R-22, R-134A, & R404A and the pressure- temperature relationship on the display corresponds with the refrigerant setting. This setting is in the UCP2 style controller factory installed on the 70-120 ton chiller. The larger RTAA's can be retrofitted with this controller also. I can't remember on the older style controller if there is a refrigerant setpoint.

  10. #22
    Join Date
    Sep 2008
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    A lot of discussion has been had about the energy costs and such, but there are some applications which this does not apply to. I have an industrial customer with an RTAA (used for air conditioning), and they are insisting that we convert it to a non ozone depleting refrigerant. The cost of R22, or of the retrofit for that matter, is not their concern. The request is driven by the company's "environmentally sound" culture. Also stems from their fear of the EPA (they tend to be extremely over-cautious in the refrigerant department). They wont even throw away a refrigerator without documentation of refrigerant recovery and disposal down to the ounce.

    With that said, could some of you seasoned guys who've done this give some tips? For me specifically, diminished cooling capacity is of no concern (this chiller is way oversized for the application). These screw compressors use oil31, which is a mineral oil. I am leaning toward one of the options where oil replacement is not required (MO99, for instance). I also read a case study from the UK of using R434A, which i dont think is that common in the US. Does anyone have any experience retrofitting an RTAA with either of these? I understand that some tweaking of setpoints may be involved, which is to be expected.

    If you were to drain and replace the oil with a POE on order to use another refrigerant, what oil would you go back with? Changing lubricants on one of these expensive screw compressors gives me an uneasy feeling. It seems like in the UK this is what they are doing, just cant find any information anywhere on it! Any help would be appreciated.

  11. #23
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    I would do my homework on the oil before I changed oil type in any screw


    Sent from my iPhone using Tapatalk

  12. #24
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    May 2012
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    California
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    Look up r434a rs-45 says drop in for r22 no changes dx or flooded systems

    Sent from my SM-G900V using Tapatalk

  13. #25
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    N
    Last edited by Dilp172; 08-17-2016 at 10:48 PM. Reason: Mistake

  14. #26
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    http://trane.ipublishpro.com/3311343...hure/index.php
    The above link is direct from Trane

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