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10 SEER evap and 13 seer condenser?

I've been told so many different things by so many different people regarding compatability of 10 and 13 SEER equipment that my head is spinning. Reps, Distributors, salesmen etc., all seem to have a different take on utilizing an existing 10 SEER evap coil with a new 13 SEER condenser. So what's the real story on this. Should the coil be changed out along with the condenser?


  • Empire_2
    Empire_2 Member Posts: 2,343
    Sorry to inturupt S Ebels

    I would if it were me. But as you know, sometimes the new 13 SEER coil is larger. I does give more actual surface area and with using the TXV which all 13 seer use it would be to your advantage....But, if that puppy aint gonna fit I see no problem with using A TXV on the 10 seer coil although you will give up some of the 13 SEER benifits..

    My 2 cents

    Mike T
  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    SEER and MPG

    How accurate is the EPA's rating on the mileage your car will actually get once you drive that new puppy off the showroom floor?

    By the EPA's own admission, the rated MPG number will be more accurate if you simply divide the rating number by 2. When calculating the sticker MPG rating, the car is in its stripped down state with all non-essential accessories removed such as spare tire, jack, hub caps, backseat, air conditioning system, etc. In addition, the car is driving downhill, with a tailwind, and attached to the back of a tow truck. Of course I'm exaggerating, but you get the idea.

    When the SEER rating of a piece of air conditioning equipment is determined, there are a number of assumptions being made. A couple of them include:

    1 - That the system capacity exactly matches the heat gain on the structure. By doing so, the system, at least theoretically, will NEVER cycle off. If the system does not cycle off, the compressor will never, with the exception of the initial startup, draw locked rotor amperage.

    2 - That the condensing unit and the air handler are located in close proximity to each other. This limits the amount of superheat added to the system in the suction line, which keeps the heat of compression (HOC in btu/lb) low. The HOC is a major contributing factor to the SEER, as is the net refrigeration effect.

    3 - That the system is perfectly charged. Anything other than a perfect system charge will affect the SEER calculations.

    4 - The air distribution system is designed perfectly. By this I mean that the proper friction rate has been used for the specific duct system and that all duct sections, transitions and fittings have been PROPERLY accounted for and taken into account when the system calculations have been made.

    So, even installing a brand new air handler and condensing unit does not guarantee that the system will operate at the rated SEER if the existing, poorly designed duct system is being reused. In addition, if the line set is long, your SEER rating will be reduced.

    To make a long story a little longer. Of course it would be better to have a matched air handler/condensing unit set, but if that is not possible, go ahead and replace the condensing unit by itself. You should though, as Mike mentioned, install a TXV on the air handler. This will help ensure that any potential overfeeding of the evaporator coil (and subsequent floodback to the compressor) will be avoided.

    Side Note:

    The difference between the EER rating and the SEER rating is that the SEER rating is intended to evaluate the system performance over the entire conditioning season, while the EER is, in essence, a snapshot of what the system is doing. The EER is directly related the the system's coefficient of performance (COP) which is found by dividing the system's net refrigeration effect (NRE in btu/lb) by the heat of compression (HOC). Multiplying the COP by 3.413 (the conversion factor between btu and watts) will provide you with the EER for the system.

    Those who will be attending the Atlanta Pressure Enthalpy Without Tears seminar on April 10th will be dealing with this concept and a whole lot more!

    Hope this helps.
  • Empire_2
    Empire_2 Member Posts: 2,343
    Which reminds me, Eugene

    Does the offer on the course of those who could not attend still stand? I think it was 60.00 or 70.00 for your literature. If not that's OK.

    Mike T
  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    Yeppers Mike.

    The PRESSURE ENTHALPY WITHOUT TEARS book, floppy disc and reference card are $60.00 flat rate. I'll take care of the shipping, etc. at this end.
  • Empire_2
    Empire_2 Member Posts: 2,343
    Thanks Gene.......................;-)

  • marco_5
    marco_5 Member Posts: 17


    > disc and reference card are $60.00 flat rate.

    > I'll take care of the shipping, etc. at this end.

  • marco_5
    marco_5 Member Posts: 17

    Is this deal through this site? I must have missed it..
  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380

    This is the book that you get asa part of the PRESSURE ENTHALPY WITHOUT TEARS seminar. If you wish to get the book, you can drop an e-mail to me at [email protected]

    It's as easy as that!
  • S Ebels
    S Ebels Member Posts: 2,322
    So Eugene, what you're saying is.............

    It depends :)

    It depends on the duct system, line set length, perfect charge, correct air flow and all that other good stuff. Right?

    There are many cases on a retrofit that will present less than ideal conditions. Probably 3/4 of them in fact. Heck, on most new houses I get into, the duct system is marginal, the condenser is parked in the next lot and the charge is anyone's guess. So what's a guy that actually cares about his work and customer to do at that point. Be honest and tell them central AC for their house is a marginal proposition?

    A basic rule of thumb on a retrofit would be to install a TXV on the evap and get the charge right on the button?
  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    It Depends!

    For a guy that cares, the important thing to do is make certain that the system is performing as well as it possibly can under the given conditions.

    By this I mean maximize the net refrigeration effect of the system and minimze the heat of compression. The heat of compression takes into account what is going on in the compressor as well as the heat that is added to the refrigerant in the suction line. By ensuring that the suction line is well insulated, you are doing the customer a great service. Next to moving the condensing unit closer to the air handler, a well insulated suction line will help increase the system's efficiency.

    As far as what the compressor is doing, the technician can do little more than ensure that the condenser coil is completely clean and that the airflow through the air distribution system is unimpeded.

    Improper airflow will cause the suction pressure to drop, which will cause the compression ratio to increase. A higher compression ration will lead to more heat being added to the refrigerant during the compression process. This causes the heat of work and the heat of compression to rise. As a result, the coefficient of performance drops and the EER and SEER follow suit.

    If you must deal with the exisxting air distribution system, it is a good idea to evaluate its layout, calaculate the TEL and ASP and see if all is withing acceptable ranges. You may very well find that by simple replacing one poorly designed elbow, you can substantially increase the efficiency of the system.

    Hope this helps!
  • don_163
    don_163 Member Posts: 67
    Well said

    Bravo..once again bravo.

    In realty nothing change.Even tho it higher seer equipment the laws remain the same.

    I find variable speed blowers helps just enough on a marginal distribution system.
    Not a cure but,will help in a pinch.
  • thp_8
    thp_8 Member Posts: 122
    Steve you know the answer.

    If you don't figure you'll use the warranty getter done. If you think you might need it, good luck with the warranty process. Look lots pipe no pumps. Well maybe a different kind. Try and propress that.
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