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Thread: R409a vs R134a

  1. #1
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    R409a vs R134a

    Went to take a look at a reach in cooler. I believe it was a Randell made in 1985. The unit was cutting out on overload. The tech before me replaced the compressor. Any way the inside temperature was around 60 degrres. I hooked up my gauges and got pressures of 30/200. The unit was in a kitchen and the ambient was 103 degrees. I know with that low suction pressure and high SH, I had a restriction. I guessed that the refrigerant used was R409a because when I shut the unit off the pressure settled down to 150-155 on the liquid side. The suction did not get much higher than 50psi. I think that the subcooling was around 9-10 degrees. Anyway I was wondering if there is any reason they stuck with R409a when they replaced the compressor rather than go with R134a?
    Stuart
    Lack of airflow destroys compressors.

  2. #2
    I think R134a is much more common for refrigeration system and heat pumps.

  3. #3
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    it depends on the compressor, was it an r12 or r134a compressor. I would only use r134a for an r134a compressor. If it was r12 compressor than thats why they used r409a. R409a is a blend for r12. My preference is hot shot but it really depends on the tech and what they like to use.

  4. #4
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    Did you look at the expansion vlv to see what kind of gas or run the compressor numbers by the supply house to see what it is? R409a you can drop right in an R12 rated system with out major changes. I have also added R409a on top of R12 with no major issues.
    Not what it use to be

  5. #5
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    Why do you think 30psi suction pressure is too low for a r-12 type system? Also, just because r-134a is more common, it doesn't mean it is a better refrigerant. For a small system that started out with r-12, r134a would be my LAST choice as a replacement. This is because the POE oil that is required with r134a is a horrible lubricant when used in the real world. It breaks down and turns to crap that will plug your cap tube if it ever over heats or has any bit of moisture in it.

  6. #6
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    Quote Originally Posted by ammoniadog View Post
    Why do you think 30psi suction pressure is too low for a r-12 type system? Also, just because r-134a is more common, it doesn't mean it is a better refrigerant. For a small system that started out with r-12, r134a would be my LAST choice as a replacement. This is because the POE oil that is required with r134a is a horrible lubricant when used in the real world. It breaks down and turns to crap that will plug your cap tube if it ever over heats or has any bit of moisture in it.
    I thought it was too low based on the conditioned space of being 55-60 degrees. I know I have a restricition/ bad TXV valve based on the high subcooling/ high superheat.
    Stuart
    Lack of airflow destroys compressors.

  7. #7
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    Quote Originally Posted by mustangpaul View Post
    it depends on the compressor, was it an r12 or r134a compressor. I would only use r134a for an r134a compressor. If it was r12 compressor than thats why they used r409a. R409a is a blend for r12. My preference is hot shot but it really depends on the tech and what they like to use.
    The compressor was just replaced with a R134a compressor. I was guessing that R409a was inside because of the higher standing pressure when the unit was shut down was closer to the P/T chart of R409a than R134a. R409a was written on the nameplate too.
    Stuart
    Lack of airflow destroys compressors.

  8. #8
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    Quote Originally Posted by ammoniadog View Post
    Why do you think 30psi suction pressure is too low for a r-12 type system? Also, just because r-134a is more common, it doesn't mean it is a better refrigerant. For a small system that started out with r-12, r134a would be my LAST choice as a replacement. This is because the POE oil that is required with r134a is a horrible lubricant when used in the real world. It breaks down and turns to crap that will plug your cap tube if it ever over heats or has any bit of moisture in it.

    What he said.....if you can't keep the coil clen then forget about it. 134 does run a bit lower hp though. IMHO opinion use 414b. 409a is garbage. 401a is even better than 409
    Only Chuck Norris can slam a revolving door

  9. #9
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    Is this a captube?
    Only Chuck Norris can slam a revolving door

  10. #10
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    Quote Originally Posted by mr kev View Post
    Is this a captube?
    I am not sure. After I told the owner about the restriction, he decided he was going to purchased a new unit since he already sunk money for a compressor replacement and it did not fix the problem.
    Stuart
    Lack of airflow destroys compressors.

  11. #11
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    These reach-in units are designed for an ambient of 80f. At an ambient of 103 all the reach-ins are getting killed.

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