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Thread: MP39 or 409a??

  1. #14
    Join Date
    May 2004
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    39
    For goodness shake gentlemen. You have been in the business long enough to know that head pressure alone is not the factor.

    So is MP39 run higher head pressure. Now a day A/C use 410A which runs at 389.6 PSIG (at 115 degrees saturate temp) is a bad thing?????

    It is all in the pressure and temperature relationship and the total amount of heat eject/absorb.

    MP39 will phase out in short future and 409A is not. Tha's the only advantage.

    Have fun

  2. #15
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    Jan 2005
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    Veterans Home Yaphank, NY
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    Frown Re : MP39 or 409A

    Stef, what did you just fall out of a tree ? High head pressure will cause extremely high compressor temperature. This will have a bearing on the oil, which will have an effect on compressor internals.
    HIGH DISCHARGE TEMPERATURE, This is the result of temperature in the compressor head and cylinders becomeing so hot that the oil loses its ability to lubricate properly. Also can cause blow by, leaking valves, and metal debris in the oil.
    You don't have to take my word, the above comes from Copeland's Electrical Handbook. I think they know a little about "Compressors". That is why Copeland is iffy about accepting 409A due to the fact that it runs higher head pressure. I back up every statement I make in this fourm,as a Teacher as well as Technician/Owner.

    [Edited by icehouse on 02-23-2005 at 04:54 PM]
    RAM Teaching Tomorrows Technicians Today.

  3. #16
    Join Date
    May 2004
    Posts
    39
    Dear Icehouse,
    Let's get back to the basic of the freon characteristics by looking at its Enthalpy (pressure-enthalpy) chart. Every freon has its own characteristic at different pressure.

    1) R12 at approximate 136 psig will lead to 110 degrees F
    2) R22 at approximate 230 psig will lead to 110 degrees F
    3) MP39 at approximate 165 psig will lead to 110 degrees F
    4) R502 at approximate 250 psig will lead to 110 degrees F

    let look closely at R12 and R502. Both has 110 degrees saturated temperature. But at 127 psig difference.

    If you plot the cycle of these two types of freon on its respective enthalpy chart assuming the following:

    a) Evaporative sateraturated temp at 0 degrees F
    b) 10 degrees F superheat
    c) 20 more degrees of heat gain when the freon pass through
    the motor
    d) Saturated condenser temp at 110 degrees
    e) assuming no subcooling for easy plotting

    You can see clearly that the discharge temperature of the R12 (which includes adiabetic heat of compression) is at appriximately 158 degrees F. The discharge temperature of the R502 is approximately at 142 degrees F.

    So please tell me if pressure has any to do with the temperatures.

    The factor that we need to closely look at is the characteristic of the freon type.

    If you look at freon R22 with the same above system, the discharge temperature is approximately 198 degrees F. Therefore R22 is not a very friendly when you use it in the low temp application because it is very hot discharge temperature.

    Thus, if you use R22 at low temp with evaportature of -40 degrees F and the same other factors, the discharge temp will be approximately 225 degrees F.

    The reason R502 was a good practice for low temp application was that it has much low temperature characteristic.

    If you look at the enthalpy chart of freon 409A you will see why it is not as good as R502 for low temp application.

    Have fun

  4. #17
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    Jan 2005
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    Veterans Home Yaphank, NY
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    Frown Re : MP39 or 409A

    Stef, very nice but we are talking MP39 or 409A not R22 or R 502. Also if you check further into your technical information you will find that R22 is indeed used on "low-temp" applications, that is why Copeland has "Demand Cooling". So instead of trying to impress everyone get your facts straight!
    RAM Teaching Tomorrows Technicians Today.

  5. #18
    Join Date
    May 2004
    Posts
    39
    Dear Icehouse,

    Indeed R22 is used in low temp application and I and no one else deny that. All I said is that R22 is not a friendly type of freon to use on low temp comparable to othe brand such as R502. The main topic is that "MP39 or R410A runs at higher pressure so that it hurts the compressor". I just want to prove that pressure is not the ONLY factor as we always look and NOT looking at the temperature and characteristic of the freon.
    As for the R409A with the same application as I gave earlier, the discharge temp is approximately 180 degrees F.
    As for MP39 the discharge temp is 178 degrees F.

    I hope that you look at the characteristic of the freon more and teach your students. Otherwise, they will be lost.

    If you go into the "refrigerant dupont" and get the characteristic of the freons and analyze with your students.

    Have fun

  6. #19
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    Jan 2005
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    Veterans Home Yaphank, NY
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    RE : MP39 or 409A

    Yes I have gone through all technical publishings on the various refrigerants (freon is the trade name for DuPont). I also have in house experiance with 409A. When it first came on the market they came to the Steamfitters Training School and I as an instructor was very impressed, however after 3 years of use we found consistant compressor failure. When we sent the compressors to Copeland the diagnosis came back as break down do to excessive temperatures caused by excessive pressures. When the breakdown of refrigerants was compared, Copeland perferred MP39 over 409A.
    Many times what looks good on paper, in actualality does not hold water.R406A was supposed to be the greatest thing since sliced bread. All the paper work made it seem like it would be the replacement of R12. However it was proved in field tests to have many problems including the high Isobutane content, used to insure oil return.
    We are now testing R420, which has pressures and temperatures close to R12, without Isobutane.
    This from ASHRE " MP39 has a slightly higher discharge temperature than R12, 409A has a significantly higher discharge temperature then R12 so caution must be used!

    [Edited by icehouse on 02-24-2005 at 04:14 PM]
    RAM Teaching Tomorrows Technicians Today.

  7. #20
    Join Date
    Jan 2003
    Posts
    539
    I nevered heard of a Lt. General running service before.
    What do I know? I was just a sergent.

  8. #21
    Join Date
    Jul 2002
    Location
    Chandler, Arizona
    Posts
    231

    Talking

    Ha Ha Comfortmaster1, I am not the General, I was a Cpl serving under him In Task Force Ripper during Desert Storm. He was my Battalion Comander 1/7 Then a LtCol. He was recently in the news back in early Feb and fired up all the liberal crybabies.

    http://apnews.myway.com/article/20050204/D881N4400.html

    Back to the subject, Stef, I get the jist of what you are saying but I have to agree with Icehouse about High Pressures having to be considered when making retrofits on old r-12 equipment.

    Jay. Semper Fi!




  9. #22
    Join Date
    Jun 2001
    Location
    Michigan
    Posts
    12,077
    I would a swapped the TX, and sold a 404a condensing unit. Done.

  10. #23
    Join Date
    Jul 2000
    Location
    Guayaquil EC
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    10,483
    That's the best long term choice, I agree wholeheartedly.

  11. #24
    Join Date
    Mar 2007
    Location
    Madison, Wisconsin
    Posts
    2,263
    I have converted literally a couple thousand Leer ice chests from either R12 or 134A to 401a. We had a lot of failed compressors and poor temps out of MP66 during the colder days of the great north. MP39 is great about keeping those cap tubes clear, and the only downside is that some old r12 tin cans can't handle the head, but if they are r12 tin cans, then it's about time to replace them any way.
    These days I try to only use the MP39 as r12 retrofit. R134A is so much cheaper that it doesn't pay to change it over for the most part, but that crap 134a plugs cap tubes at the first hint of an overheated compressor.

    I r the king of the world!...or at least I get to stand on the roof and look down on the rest of yall

  12. #25
    Join Date
    Mar 2007
    Location
    Madison, Wisconsin
    Posts
    2,263
    Quote Originally Posted by asproegypt1 View Post
    Hi
    I was searching for anything to re-charge my R-123a So I found Something Maybe It Will Be More Useful For Your Issue And

    otherwise it helps me too

    Here
    I r the king of the world!...or at least I get to stand on the roof and look down on the rest of yall

  13. #26
    Join Date
    Sep 2002
    Posts
    13,545

    Why not R-414? The Hot Shot stuff

    I like it better than R-409 and it is also a drop-in which works fine with any oil.
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

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