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  1. #1
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    Why do household freezers use R12/134a rather than 404A/502?

    Looking at the PT chart, they're near or below atmospheric pressure with evaporator temperatures seen in freezers.

    R22 apparently has issues with high discharge temperature issues leading to refrigerant decomposition.

    It seems like almost all household freezers for many many years used R12 and R134a exclusively. Why not R502 or 404A?

  2. #2
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    I thought someone sharper than me would have answered by now, but-

    R-12 was around for a long time before 502. Maybe the manufacturers were comfortable with 12 in their testing and design. Then came the EPA-

    134-A has a GWP of 1430 and a ODP of 0.

    R-404A has a GWP of 3300 and an ODP of 0.

    So my guess is 134-A is more environmentally friendly according to the EPA.

    Ozone Depletion Potential (ODP) of a chemical compound is the relative amount of degradation it can cause to the ozone layer

    Global Warming Potential (GWP) is a measure of how much a given mass of a gas contributes to global warming. GWP is a relative scale which compares the greenhouse gas to Carbon Dioxide where GWP by definition is 1.


    Please don't shoot the messenger! Just putting out ideas. I have always used 404A on built-up sytems, medium and low temp- never 134-A.
    Experience is what you have an hour after you need it.

  3. #3
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    Interesting Question

    But te above is pretty much right. R12 was here, being used, why change? When the EPA decided to put their foot, fist and face down... manufactures had a choice. Use a refrigerant that requires very little system design change or spend the R&D money to re-design the whole thing.

    Something else interesting, that I thought about while writing this. I do not think I have ever seen r404 in a system with less than a pound of refrigerant in it. It's always 134.

    I can't fix it if it won't stay broke..

  4. #4
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    As the previous posted said, the manufacturers were comfortable with R12 and R134A, so why change?

    If you consider the track record of domestic refrigerator/freezers over all these years, their reliability has been extremely good. For whatever issues they may have, I'd say refrigerant related problems are very rare.

    I suspect the efficiency entered into their decision as well, what with the drive for better Energy Star ratings and such.

    I'm sure if an alternate refrigerant like R404A had offered any substantial benefit in production cost, reliability or efficiency they would have changed in a heartbeat, but apparently the benefits simply weren't there.

    I find it interesting to watch what's going on around the globe. R134A is rising fast on the hit list for many countries due to its global warming potential, so natural refrigerants like R290 (Propane) and CO2 are becoming more popular.

    R290 is actually a very good refrigerant, quite similar to R404A in its performance, but due to its flammability I doubt we'll ever see it here in the States. More likely, it's time for us to be prepared for CO2.

  5. #5
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    Quote Originally Posted by icemeister View Post
    R290 is actually a very good refrigerant, quite similar to R404A in its performance, but due to its flammability I doubt we'll ever see it here in the States. More likely, it's time for us to be prepared for CO2.
    When you just look at the PT chart, R22 actually looks like a good refrigerant for low-temperature due to fair evaporation pressure. It apparently has high compression heat to the point of refrigerant decomposition that leads to valve build-ups.

    How is the discharge temperature on R290?

  6. #6
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    That's funny you posted this since I was thinking about this the other day also. Ice- why is 134a not used on larger box setups? I see almost 404 exclusively. We have 2 boxes with 12 and 1 with 502 but none using 134??

  7. #7
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    Quote Originally Posted by icemeister View Post
    More likely, it's time for us to be prepared for CO2.
    The operating pressures are outrageously high with CO2 that it makes R410A looks like a child's play.

    There is an extensive PDF report somewhere about using CO2 in automotive A/C. It's apparently not as efficient as traditional medium pressure refrigerants and incurs greater GWP from increased tailpipe emissions than refrigerant leak induced GWP.

  8. #8
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    Quote Originally Posted by ICanHas View Post
    The operating pressures are outrageously high with CO2 that it makes R410A looks like a child's play.

    There is an extensive PDF report somewhere about using CO2 in automotive A/C. It's apparently not as efficient as traditional medium pressure refrigerants and incurs greater GWP from increased tailpipe emissions than refrigerant leak induced GWP.
    That may well be true, but we're more concerned about refrigeration.

    If you consider a typical fractional horsepower commercial cooler and compare apples to apples, I believe the R134A system will be more efficient than a transcritical CO2. However, if the CO2 system is souped up a bit...or "optimized"...it can be significantly more efficient than a standard R134A system.

    Here's a report of how a transcritical CO2 system in a Coke vending machine has 17% lower energy consumption than the standard R134A unit:

    http://www.epeeglobal.org/epeedocs/i...orEPEE_925.pdf

  9. #9
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    Quote Originally Posted by ryan1088 View Post
    That's funny you posted this since I was thinking about this the other day also. Ice- why is 134a not used on larger box setups? I see almost 404 exclusively. We have 2 boxes with 12 and 1 with 502 but none using 134??
    Personally, I opt for R404A on all new systems because it performs better in my opinion. Smaller line size requirement is a factor as well.

    Also, if you check out what's available for R134A hermetics, they tend to stop at 1 1/2 or 2 HP. To go any larger you'd need to go with semihermetics or a scroll...which would mean +++$$$. So if you're cost concious and your walk-in needs a 3, 4 or 5 HP unit, you choose an R404A hermetic.

  10. #10
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    Quote Originally Posted by icemeister View Post
    That may well be true, but we're more concerned about refrigeration.

    If you consider a typical fractional horsepower commercial cooler and compare apples to apples, I believe the R134A system will be more efficient than a transcritical CO2. However, if the CO2 system is souped up a bit...or "optimized"...it can be significantly more efficient than a standard R134A system.
    I believe "souping up" can be applied to any system including the use of optimized condensers and evaporators that may cost more as well the use of more advanced motors that offer superior efficiency.

    MVAC and refrigeration operate at different tempreatures, but the principle is the same.

    Here's a report of how a transcritical CO2 system in a Coke vending machine has 17% lower energy consumption than the standard R134A unit:

    http://www.epeeglobal.org/epeedocs/i...orEPEE_925.pdf
    There's a report on the use of R410A in place of R404A as well for refrigeration.
    http://www.ideals.illinois.edu/bitst...Rajan_Suri.pdf

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