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410A vs R22

Depends on how old the evap is? If it has any age at all you will need to replace the evap to match the new condensing unit, a little thing about SEER ratings and such. Some old evaps were dual rated, but if you install a new 13 Seer unit you will need to match the evap to the cond. to get the proper Seer rating and capacity that the new condensor is rated.

You can go to the ARI website and see how the units match up and what the Seer level and capacity are.

Don in Mo


  • ddenny
    ddenny Member Posts: 75
    410A vs R22

    hello Dr. silberstein
    is the evaporator for an R-22 system different from one in a 410A system.? how is it different? suppose I want to replace an old R-22 condinsing with a new 410A system. what would I have to do to the evaporator?
  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    R-410a Systems

    Greetings Dennis,

    Chances are that you would have to replace the evaporator as well. Putting the efficiency issue aside for a moment, let's take a look at the operating pressures.

    R-410a operates at pressures that are about 70% greater than those of R-22. So, to get your 40-degreee coil on an R-22 system, your low side pressure will be about 68.5 psig. On an R-410a system, however, the low side pressure will be about 118 psig. Although this may not seem to be a big deal, it is... Here's why.

    When equipment (coils, etc.) they are all pressure tested at the factory. evaporator coils for use on R-22 systems are factory pressure tested to 150 psig. If you chose to use your existing R-22 evaporator for R-410a, you will be operating very close to the test pressure for that coil.

    Evaporators (indoor coils) that are designed for heat pump use are pressure tested to 235 psig. This coil can be used in conjunction with R-410a.

    Here is a very easy solution to your situation. GO WITH R-407c!

    R-407c is a great option for R-22 retrofitting. R-407c is basically a mixture of R-410a and R-134a. The operating pressures for R-407c are very similar to those for R-22, so you don't have to worry about the pressure problems associated with R-410a. The main drawback woith R-407c is that, since it is an HFC refrigerant blend, the oil (ester-based) is not compatible with that used in R-22 systems. But, since you plan on replacing the condensing unit, this will not pose a problem.
  • Paul Fredricks_3
    Paul Fredricks_3 Member Posts: 1,549

    Not familiar with 407c. Does this stay blended, in other words, if you get a leak do you have to remove the rest of the refrigerant and then recharge? Are any manufacturers using it in their new equipment?
  • Brad White_9
    Brad White_9 Member Posts: 2,440
    Good question

    We have been having the same debate in our office regarding using azeotropic and zeotropic blends, exactly for the reasons you state.

    If one does have a leak with a zeotropic blend (a blend that separates at different temperatures and pressures essentially), does one have to dump the charge and re-charge from scratch? The 400 series falls into this (407c for example). If one does have to recharge, is it practical to 'crack off' each component and recover them or can one assess the remaining mixture? Or does it have to be disposed of?

    With azeotropic blends (blends that boil and condense at the same temperature and pressure), am I correct in assuming that a leak can be topped off and not upset the blend percentages?

    Your question just raised that again.
  • Paul Fredricks_3
    Paul Fredricks_3 Member Posts: 1,549

    We asked this question at at 410a class we took last year. We were told that the refrigerants used in the blend that is 410a are so close to each other that they basically don't separate. There is no need to recover in order to charge after a leak is repaired. Curious if 407c is the same. Though it doesn't really matter if no one is putting it in a new system.
  • jwade55_5
    jwade55_5 Member Posts: 14
    Temperature glide.

    a zeotropic (blended) refrigerant has a characteristic that refers to the range of temperatures at which components boil or condense at a given pressure. With a system using a zeotropic blend with a high temperature glide, the more volatile components will escape first if there is a leak while the system is off, this is fractionation. While the system is running the refrigerant stays blended, and a leak is less likely to result in fractionation. This complicates the charging process of a blended system.
  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    Temperature Glide

    Temperature glide ranges from 0.2 degrees to 16 degrees. R-410a has a temperature glide of 0.3 degrees, so we tend to ignore it. R-407c on the other hand, has a temperature glode of 10 degrees, mainly because of the R-134a component in it. So, if there is a leak, the charge should be recovered and replaced with fresh, virgin, R-407c. Depending on the specific circumstances, it may be beneficial to go this route, especially if replacing the air handler is going to be a logistical nightmare.
  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380

    Azeotropic refrigerant blends are classified as the 500 series refrigerants, such as R-500 and R-502.

    The 400 series refrigerants are classified as near-azeotropes or azeotropic blends as they have a temperature glide. As mentioned, the temperature glide of R-410a is practically non-existent at 0.3 degrees, so we tend to treat if as a single compound refrigerant.
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