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  1. #1
    I am shopping for a new electric heat pump rooftop package in Phoenix. I have consulted three reputable HVAC contractors. Two of them are suggesting R-22 units, and one is suggesting R410. All three contractors have both R-22 and R410 units to offer.

    The two contractors suggesting the R-22 units say R410 units run higher head pressures and need more subcooling. These R410 characteristics combined with very high ambient temperatures (especially for rooftop packages sitting on brown roofs) have led to greatly reduced cooling capacities and higher failure rates for R410 units on very hot days.

    I e-mailed a few manufacturers asking if R410 was appropriate for the Phoenix area. In all cases the answer was "ask your dealer".

    I have read other threads in this forum regarding the R410/R-22 debate, but could not find any information regarding R410's suitability for areas like Phoenix.

    If it makes any difference, I am looking for a 4 ton unit with a 13 SEER

    Any comments would be appreciated.

    Thank you.

  2. #2
    Well, the 'higher subcooling' for the 410 is pure BS.

    Both refrigerants require subcooling, it's just that 410 operates at a higher pressure.

    The 410 has it's dis-advantages, but is a more efficient refrigerant of the two listed. 410 will be the next common 'everyday' refrigerant of the HVAC industry.

    All that said, I'd go for the R22 unit with a scroll compressor!

  3. #3
    Join Date
    Jun 2004
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    146
    This research paper suggests R410A loses both capacity and efficiency faster than R22 at higher temperatures. Assuming all else is equal, R22 seems to be the better choice for hot weather climates like Phoenix.

    http://www.bfrl.nist.gov/863/HVAC/pu...nt%20tests.pdf

  4. #4
    Interesting article...

    That sure contradicts the info given at every tech seminar (on 410) that I have attended!

  5. #5
    Join Date
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    Holy crap! I usually dismiss both the 410-A naysayers and the R-22 detractors. They both typically have a lot of unprovable predictions and hot air. But this is something VERY different. If this study has come up here before I'd sure like to see the thread.

  6. #6
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    Interesting indeed but I dont think it should be overread. In a nutshell, it pointed out that at 95 there was a 4% lower efficiency and at 120 about 15%. However, at lower temps the R-410A was more efficient. You also have to consider the indoor WB temps used in the tests which indicate a latent load. at 105 outside with an indoor temp of 80 and 45% rh you would use a 65 wb versus a 67 in the tests. This is significant. I understand the test criteria but short of Houston, where would we see the occasional 105+ day where the humidity was an issue. Cetaily not Phoenix which is in question here.

    Taking that into account. In Phoenix, a 30 year trend shows an average high temperature of May- 93.6, June-103.5, July 105.9, Aug 103.7, Sept 98.3. The average Lows for these months are May-63.9, June-73.9, July-81.0, Aug-79.2, Spet 72.8. (obviously these are the warmest months).

    Now, my point is when we thin Phoenix we think Hot. And it is. In fact there are a few days each year where 115 degrees is possible for a few hours. But over the life of the cooling season it isnt always that hot. At night it is generally cooler than mid-day but is it still not cooling conditions? Is the cooling season not from Mid March to November?

    Again, yes there are extremes but extremes are not the norm. What if I took all those numbers from the cooling season, average temps, average highs, average lows recoed highs, record lows and came to a median temperature. Would it then be an issue? I think not.

    The question should be is there a sizing issue from one to the other based on capcity. When I look at the charts, I see J-8 uses 107 or 108 as the design temp. If this is the case, then it may seem that the system at full design would need to be roughly 8% larger. In other words a 30,000 btuh load would reqire a machine with an output of 33,000. If on the other hand, I consider the low coincident wet bulb temps, I can then assume a low humidity. In fact, very low humidity. Simple increase in CFM to 450 or even 500 CFM per ton increases my sensible capacity maybe enough to absorb the difference. Maybe not.

    Again, its good to see testing like this being performaed and documented but I think the argument would be a poor consideration for real world application. One should never apply variable data to only extremes. This is what HP naysayers do regularly whith no actual understanding.

    Why apply this argument to 3 or 5% of the season ignoring the remaining 95 or 97% of the season?



    [Edited by docholiday on 07-07-2005 at 11:13 AM]

  7. #7
    Join Date
    Aug 2002
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    Doc,

    Nice job,but those looking for reasons/excuses not to move to Puron/R410a,will see it the way they want to.

  8. #8
    Join Date
    Jun 2004
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    146
    Originally posted by docholiday
    Interesting indeed but I dont think it should be overread. In a nutshell, it pointed out that at 95 there was a 4% lower efficiency and at 120 about 15%. However, at lower temps the R-410A was more efficient. You also have to consider the indoor WB temps used in the tests which indicate a latent load. at 105 outside with an indoor temp of 80 and 45% rh you would use a 65 wb versus a 67 in the tests. This is significant. I understand the test criteria but short of Houston, where would we see the occasional 105+ day where the humidity was an issue. Cetaily not Phoenix which is in question here.

    Taking that into account. In Phoenix, a 30 year trend shows an average high temperature of May- 93.6, June-103.5, July 105.9, Aug 103.7, Sept 98.3. The average Lows for these months are May-63.9, June-73.9, July-81.0, Aug-79.2, Spet 72.8. (obviously these are the warmest months).

    Now, my point is when we thin Phoenix we think Hot. And it is. In fact there are a few days each year where 115 degrees is possible for a few hours. But over the life of the cooling season it isnt always that hot. At night it is generally cooler than mid-day but is it still not cooling conditions? Is the cooling season not from Mid March to November?

    Again, yes there are extremes but extremes are not the norm. What if I took all those numbers from the cooling season, average temps, average highs, average lows recoed highs, record lows and came to a median temperature. Would it then be an issue? I think not.

    The question should be is there a sizing issue from one to the other based on capcity. When I look at the charts, I see J-8 uses 107 or 108 as the design temp. If this is the case, then it may seem that the system at full design would need to be roughly 8% larger. In other words a 30,000 btuh load would reqire a machine with an output of 33,000. If on the other hand, I consider the low coincident wet bulb temps, I can then assume a low humidity. In fact, very low humidity. Simple increase in CFM to 450 or even 500 CFM per ton increases my sensible capacity maybe enough to absorb the difference. Maybe not.

    Again, its good to see testing like this being performaed and documented but I think the argument would be a poor consideration for real world application. One should never apply variable data to only extremes. This is what HP naysayers do regularly whith no actual understanding.

    Why apply this argument to 3 or 5% of the season ignoring the remaining 95 or 97% of the season?
    I'm not related to the HVAC industry so I've no reason to prefer one over the other. I just read this stuff for amusement. And in my area the average summer high temperature is 76F where R410A is probably better.

    In regards to your comment about latent load, while humidity could have affected the results, there's no indication about which way the results would have been affected. Removing the latent load may have increased, decreased, or not affected the degradation of R410A versus R22 at higher temperatures.

    Looking at the graph in the study, R410A was about as efficient as R22 at about 90F. But it's worth noting that the R410A equipment was a 13 SEER while the R22 was 12.5 SEER. So the R410A equipment should have been about 4% more efficient. If you adjust for the SEER rating difference, the R410A was less efficient than the R22 down to almost 80F.

    And comparing what percentage of the cooling season is above or below that temperature isn't useful. It's what percentage of the AC run-time is above/below that temperature that matters. R410A may be more efficient at lower temperatures, but the AC doesn't run much at lower temperatures. While at higher temperatures, it may be running non-stop.

  9. #9
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    It's worth noting that manufactures have yet to design coils ,based on R410a,when they do I think you'll see different(closer maybe not the same),results.

  10. #10
    Join Date
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    Originally posted by dash
    Nice job,but those looking for reasons/excuses not to move to Puron/R410a,will see it the way they want to.
    Sometimes, Dash, I wonder why you are so stuck on R410a in that is the only replacement refrigerant way to go. I still believe there might be a nearly to exact drop-in cost effective replacement showing up in the futrure.

    But your statement can be used equally opposite for those that neeed or want to justify R410a with "but those looking for reasons/excuses to move to Puron/R410a,will see it the way they want to."

    I found the article extremely interestiing only on a technical basis. I'll go either way, as I have said before on R410a. And once the market proves itself out in the years to come, I will simply accept and move into that market of replacement refrigerant.

    And, by they way, I now have R410a on my truck for the extremely few systems I have now. If I get more fine, if not, also fine.

    From the article I can see a resoning for me to be concerned with customers that have or might get roof top package or split systems containing R410a. Even in my mild climate, a roof top full of package/split units located on a shopping mall roof can get temperatures in excess of 130 degrees with the reflection of the sun and combined heat loads from placement and other systems loads.

    I think any intelligent person will read the technicallities of this well done and precise article and make up their own mind as to how it applies to them.
    "The American Republic will endure until the day Congress discovers it can bribe the public with the public's own money.
    - Alexis de Toqueville, 1835

  11. #11
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    I've heard the opinions of mfrs,both equipment and compressors,I'm convinced R410a is it,and it's very unlikely that there will be a cost effective,acceptable drop in for R22.

    This of course, doesn't mean it's so,nor does it mean it's not so.


  12. #12
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    I'm not sure who you're referrig to Dash. But if ever there were a water carrier it has to be you. You're technical qualifications are not in doubt. But reading your posts one would think that you must always pick Carrier, always choose 410-A and always put in high end filtration. I'm sure you'd disagree with that assessment and that's OK.

    My personal philosophy on all of those topics is summed up with the word "whatever". Whatever the customer wants I'll give them so long as it isn't a scam. Brand and refrigerant types have little meaning to me because you simply can't prove one is better than the other. The day that you can will be the day I change my mind. Perhaps this study is a step in that direction. But in the mean time I remain open minded about any brand and any refrigerant. That doesn't seem to be the case with you, which is the very thing you seem to be criticizing of others.

  13. #13
    Join Date
    Nov 2004
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    Originally posted by DeltaT
    [BI think any intelligent person will read the technicallities of this well done and precise article and make up their own mind as to how it applies to them. [/B]
    What does it mean to me?
    Uhh...
    I got me some super heavy-duty gauges out of the deal!

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