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Thread: I need HELP!

  1. #1

    Confused I need HELP!

    I live in the Dallas, Texas area. My AC unit just went out and am contemplating getting a new system. I have read about SEER, etc and have rudimentary understanding of what I am dealing with but still consider myself dumb enough to be buffaloed by contractors.

    I have heard/read good things about Trane, Lennox, Carrier, Tappan
    systems to the point I am totally confused. Such as how a Trane xl19i can be rated as energy efficient but consume more electricity because of the dual compressors(?). How come Tappan (fantstic new technology) does not show up as a top rated or most popular system?

    Can anyone point me to a good system for use in this area (ie, do I really need a 20 SEER unit in this geographic area?)

    Any help would be appreciated.

  2. #2
    Join Date
    Jul 2008
    Location
    TX
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    32
    I was recently in the same situation. My AC went out on me and needed to be replaced. I'm clueless about anything related to AC systems.

    Based on my experience with my new AC install and from the expert advice here, you might be better off asking for recommendations for a good contractor rather than equipment.

    If it's feasible, you might want to snag a window unit to at least cool the bedroom for a few days so you can take your time to find the right guy to do the job.

    Just a suggestion from a fellow uneducated consumer...

  3. #3
    Join Date
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    The technology that the Tappan uses, is relatively new to the split system market.
    Only been out about a year.

    Don't know why any one told you the 19i uses more electric. Only one compressor runs at a time. May be that the contractor that told you that doesn't know how they work, or it was his attempt at scamming you into using him.

    2 stage systems provide greater comfort then single stage systems. So if your interested in 2 stage systems for great money savings on operating cost. Your looking at them for the wrong reason.

    Find a good contractor. He won't bash brands. He won't promise you the system can do more then it really can. And you'll be happier that you didn't just buy a brand name.
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  4. #4
    Join Date
    Jun 2005
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    SW Wisconsin
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    For Dallas, TX summer design 100-F dry bulb, 75-F wet bulb, that is a low Relative Humidity.

    A good install & setup with optimized ductwork & airflow, is far more important than mere SEER Rating or equipment brand!

    With high SEER units' the compressor BTUH is lower than the condensing unit rating.(Just food for thought..)

    With that low a humidity, I personally would want at least a 450-CFM airflow through a wet evaporator coil. My preference is to get an optimal heatload through the coil to optimize the nominal BTUH operating performance.

    Regarding SEER rating, I don't know what the price spread is in your area, but the higher you go with SEER & EER the more difficult it is to achieve it. If you size correctly cycling should not be a big efficiency factor with a lot of high temperature hours.

    In more moderate climates, 80 to 88°F I would select smaller BTUH units per load especially where humidity is low - to reduce cycling that gobbles up efficiency.

    The SEER of a system is determined by multiplying the steady state energy efficiency ratio (EER) measured at conditions of 82°F outdoor temperature, 80°F dB/ 67°F wb 50% RH indoor entering air temperature by the “Part Load Factor” (PLF) of the system. (Laboratory conditions.)

    The PLF is a measure of the cyclic performance (CD) of a system and is calculated as follows: CD is Cyclical Data
    PLF = 1.00 - (CD X's 0.5)

    "The cyclic performance (CD) value in the above equation has been determined by the government to be 0.25." The government contends that the PLF should equal:
    [1.00 - (.25 x .5)] = .125
    1.00 - .125 = 0.875, which yields: PLF of 0.875
    A 3-ton system would be 36000 X's PLF .875 = 31500-btu/hr, or closer to 2.5-ton 30000-btu/hr system.
    A 4-ton system 48000-btuh X's .875 = 42000-btuh or a 3.5-ton PLF operating system. - udarrell

  5. #5
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    Udarrel.
    Do you think the system SEER selection should be based on the 1500 plus hours Dallas has between 80 and 90(not to mention the 940 plus hours between 75 and 80), or the 800 hours above 90.

    Talking SEER only, no other factors.
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  6. #6
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    A SEER Rated system with components to cover all three categories

    Quote Originally Posted by beenthere View Post
    Udarrell.
    Do you think the system SEER selection should be based on the 1500 plus hours Dallas has between 80 and 90(not to mention the 940 plus hours between 75 and 80), or the 800 hours above 90.
    Talking SEER only, no other factors.
    You did an important & good job researching the weather history of the Dallas area, that is very important when selecting SEER as well as sizing considerations & other component options.

    I would want a SEER Rated system with components that would efficiently & effectively cover all three categories.

    In that low humidity climate it does appear that a higher SEER might work okay especially if it were variable capacity. If it is going to be a high SEER, I would only want it as a variable capacity system.

    However, a variable capacity system in 14 to 16-SEER with a little lower EER & therefore lower evaporator Suction pres/temps per the load level, would still be my personal preference.

    It would need a variable speed AH blower.
    I suppose I might have to go to 16-SEER to get the variable cooling capacity.

    Room T-stat would need to be adjustable for cycles per hour, or preferably an adjustable setpoint temperature differential for the moderate temperatures.

    CA research indicates that in a variety of climate conditions the higher SEER units seldom meet their SEER Ratings.

    California Research Report on EER SEER
    http://www.energystar.gov/ia/partner...ndices_A_B.pdf

    Excellent post as usual - beenthere, revealing very important data toward better decision making options.

    Since I have been retired for quite some time, I would tend to defer to your evaluation of this particular Dallas situation. - udarrell

  7. #7
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    We all tend to think places that have long cooling seasons like Dallas, are always above 95, when often they are not.
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  8. #8
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    2 stage can be beneficial in his area, as it gets to the 95 plus temps, it will jimp to second stage fairly quick. Then when its in teh 80 to 90's, he get teh saving of being 2 stage again.

    Thermostat selection can be as important as coil match up.
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  9. #9
    Join Date
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    The most important part is a great contractor that will do a quality install after a load calc. and stand behind their work...and definitely buy the PM agreement.
    The man who smiles when things go wrong has thought of someone to blame it on. - Robert Bloch

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