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  1. #40
    Join Date
    Sep 2008
    Location
    Western PA
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    25,870
    Quote Originally Posted by cy View Post
    nope... I was asking ... so if I'm reading correctly. it's not possible for a wrong charge alone to contaminate oils?
    I don't see a way that it can happen.

    POE oil is ALMOST universally compatible with the exception of R12 which is really a non-issue today.

    Even if you added an HFC to mineral oil system, it won't damage the oil, there are just miscibility issues with HFCs and mineral oil.

    Refrigerants, to my knowledge, do not chemically alter oils.

  2. #41
    Join Date
    Oct 2010
    Location
    Baton Rouge, LA
    Posts
    1,114
    Hey, I noticed you have a flat tire on your car. We are gonna throw this doughnut tire on it. No, you don't have to worry. You can still do 80 miles an hour on the highway. You don't need to replace it with a full spare, ever.

    That's why you don't mix refrigerants, not because of what you can do, because of what could be.
    If you're too "open" minded, your brains will fall out.
    Artificial intelligence is no match for natural stupidity.

  3. #42
    Join Date
    Apr 2007
    Location
    Kaufman county, Texas
    Posts
    10,433
    Quote Originally Posted by OldSchoolMech View Post
    I have read this from the start and think that making a "Cocktail" Is dumb and unneeded. I can see the just a little bit when in a pinch. But to do it and Brag about it EPA anyone????
    I don't think anyone here condones mixing refrigerants. Just goofy situations we get in to.

    Neither do I think the EPA is policing our activities. They are collecting a fee and leaving us alone. For now.
    "You boys are really making this thing harder than it has to be". Me

    "Who ARE you people? And WHAT are you doing in my SWAMP!?" Shrek

    Service calls submitted after 3PM will be posted the next business day.

    I give free estimates [Wild Ass Guesses] over the phone.

    "I am sorry for interrupting, please continue with your quarreling" Some chick on TV

  4. #43
    Join Date
    Oct 2008
    Location
    Massachusetts
    Posts
    43

    Blood Bank Freezer w/2 Refrigerants By Design

    I've got a customer (a Hospital) with a small blood freezer which takes both 404 and 134 per the manufacturer. we were all scratching our heads at this one.

    It's made by Thermo Scientific. I've got to change out the compressor which failed after 7 years.

    Uses a Copeland compressor.

  5. #44
    Join Date
    Aug 2010
    Posts
    3,509
    Quote Originally Posted by jtel View Post
    I've got a customer (a Hospital) with a small blood freezer which takes both 404 and 134 per the manufacturer. we were all scratching our heads at this one.

    It's made by Thermo Scientific. I've got to change out the compressor which failed after 7 years.

    Uses a Copeland compressor.
    Are you sure its not a dual system? I'm guessing it takes 134a for one section and 404 for another.

    If it's a cascade system I'm guessing 134a for high side loop and 404 for low stage, so that it doesn't have to go from -40 (or whatever it is) to 100F ambient in one step.

  6. #45
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,870

  7. #46
    Join Date
    Oct 2008
    Location
    Massachusetts
    Posts
    43
    I am absolutely sure that this is a single system. At one point I went out to double check that and since then I've been on the phone with the manufacturer several times.

    This is not much bigger than your average size college dorm refer and new it costs $7k.

  8. #47
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,870

  9. #48
    Join Date
    Jan 2010
    Posts
    6,615
    Quote Originally Posted by jtel View Post
    I am absolutely sure that this is a single system. At one point I went out to double check that and since then I've been on the phone with the manufacturer several times.

    This is not much bigger than your average size college dorm refer and new it costs $7k.

    So what P/T chart do you use ?

  10. #49
    Join Date
    Jun 2003
    Location
    Chicago, IL
    Posts
    4,538
    Quote Originally Posted by VTP99 View Post

    So what P/T chart do you use ?
    I would assume you would use the p/t chart that applies to the refrigerant that is at a saturated condition in the portion of the system you are diagnosing.

    In reality I don't think you would use a P/T chart on an autocascade. I think if you suspect a refrigerant problem, you would pull the charge and weigh in virgin charge of each of the components

  11. #50
    Join Date
    Jul 2012
    Location
    Baton Rouge Louisiana
    Posts
    179
    I had somebody try to tell me yesterday that they put R22 in a 410a system and it worked better than ever. I questioned the pt chart. How could you possibly ever get superheat or subcool? Are there any other problems that come with mixing r22 and 410a?


    Sent from my iPhone using Tapatalk

  12. #51
    Join Date
    Apr 2007
    Location
    Kaufman county, Texas
    Posts
    10,433
    Quote Originally Posted by Bmvbrfd View Post
    I had somebody try to tell me yesterday that they put R22 in a 410a system and it worked better than ever. I questioned the pt chart. How could you possibly ever get superheat or subcool? Are there any other problems that come with mixing r22 and 410a?


    Sent from my iPhone using Tapatalk
    Mixing refrigerants obsoletes any P/T chart.
    "You boys are really making this thing harder than it has to be". Me

    "Who ARE you people? And WHAT are you doing in my SWAMP!?" Shrek

    Service calls submitted after 3PM will be posted the next business day.

    I give free estimates [Wild Ass Guesses] over the phone.

    "I am sorry for interrupting, please continue with your quarreling" Some chick on TV

  13. #52
    Join Date
    Oct 2008
    Location
    Massachusetts
    Posts
    43
    I've never worked on this before and we are still waiting for the compressor.

    I asked ThermoScientific if there was a preference for which gas is weighed in first and they said 404a first then 134a although that may not mean anything.

    Quote Originally Posted by VTP99 View Post
    So what P/T chart do you use ?

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