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  1. #53
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,428
    Quote Originally Posted by Zomby View Post

    I have decided to go with the 2 ton unit. I am basing this on what the contractors said on their initial visits as they all suggested 2.5 or less, but also on what information I have gathered from this post as well as digging through the archives here.

    Once the decision is made, I am stuck with it either way!
    How many automobiles do you review when you are about to buy a car?
    There must be 200 models now with 20+ options providing for 10,000's of options.

    Apparently, it may take years for one to decide whether a 4 or 6 cylinder is optimum for the next 15 years.
    After all, one only needs a 4 cylinder if there is a driver and 2 passengers are riding.
    However, it's not going to work optimally when there are a total of four people riding in the mountains.
    Of course, out of 200,000 miles one might drive in ~15 years,
    the extreme case of an engine being 'maxxed out' may only apply for 3,000 miles / < 2% of the time.

    I guess going 59 MPH instead of 66 MPH for a total of 50 hours in 15 years is going to be an interesting dilemna to face
    when one tries to determine which of 10,000's various auto characteristics permutations one might foresee
    in selecting that efficient, favorite brand, optimum vehicle.

    I'd buy that comfort machine that's going to satisfy me > 96% of the time/ a.k.a. 2,880 hours out of 3,000 "summer time hours"
    and be prepared to enjoy the temperature over 79'F inside for ~120 hours a year when it might be > 99'F outside.
    Of course, I'll probably be working, visiting, shopping, in the pool, at the beach or at the movies half that time,
    so I won't even notice the 80'F inside for 60 hours of the total.
    And if my $30 fan doesn't satisfy me with a little more cooling,
    I can always go to the bar and talk about my dilemna.
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  2. #54
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
    Posts
    4,503
    Don't forget Man J also includes certain internal gains. Those appliances can be switched off for a few hours during the 2% of the summer.

  3. #55
    Join Date
    Jul 2008
    Location
    Rochester NY
    Posts
    4,763
    Lol

    Dan funny Dam.

    Hey, don't forget the 240 light load hours that your smaller unit actually makes your home MORE comfortable than the oversized unit would. and all that dough in your pocket from equipment and energy savings!
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

  4. #56
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,376
    Dan is correct. The only time a "right sized" or slightly undersized system might deliver a lack of complete comfort is during the worst days of the year, which in comparison to the entire year cooling requirement is a small amount of time.

    Even those "worst day" events could be narrowed a bit by paying attention to the house building envelope, such as insulation levels, radiant barrier or "cool roof" options, air sealing, etc.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  5. #57
    Join Date
    Jul 2008
    Location
    Rochester NY
    Posts
    4,763
    Quote Originally Posted by Shophound View Post
    Dan is correct. The only time a "right sized" or slightly undersized system might deliver a lack of complete comfort is during the worst days of the year, which in comparison to the entire year cooling requirement is a small amount of time.

    Even those "worst day" events could be narrowed a bit by paying attention to the house building envelope, such as insulation levels, radiant barrier or "cool roof" options, air sealing, etc.
    They could be further narrowed by dropping the tstat setting a few degrees in advance of the weather events - kind of like gaining speed before going over a hill.

    On Monday when you see it's going to be 101f on Friday, move the thermostat from 75 to 72 and pull some BTU out of the house's mass.
    Which makes more sense to you?
    CONSERVATION - turning your thermostat back and being uncomfortable. Maybe saving 5-10%
    ENERGY EFFICIENCY - leaving your thermostat where everyone is comfortable. Saving 30-70%

    DO THE NUMBERS! Step on a HOMESCALE.
    What is comfort? Well, it AIN'T just TEMPERATURE!

    Energy Obese? An audit is the next step - go to BPI.org, or RESNET, and find an auditor near you.

  6. #58
    Join Date
    Nov 2009
    Location
    Kansas City
    Posts
    124
    Quote Originally Posted by Zomby View Post
    First, thanks to everyone who has helped me get to this point. Your knowledge and assistance has been extremely helpful!

    I have narrowed it down to Trane or Bryant and would appreciate your thoughts on the 2 systems.

    My hose is as follows:

    1,500 s/f single-story ranch over a crawlspace.
    Mid Missouri
    3 ton condenser - 9 SEER
    75,000 btu gas furnace

    Trane contractor suggested the following:

    XR15 2-ton single stage condenser - 16 SEER
    XV95 2-stage, variable speed gas furnace
    "matching coil"
    TCONT thermostat

    Bryant contractor suggested the following:

    127A 3-ton two stage condenser - 16.5 SEER
    96T 2-stage, variable speed gas furnace
    CNPV*3717A** indoor coil
    T6 Thermostat


    As you can see the biggest difference I see if the condenser unit. Trane being 2 ton single stage and Bryant being 3 ton two stage. The Bryant contractor said a 3 ton two stage would serve me much better than a 2 ton single stage.....

    As far as I know, they both did pretty much the same load calculations.

    Any thoughts would be more than appreciated!
    You should have gone with the 3ton two stage. If you have 1500 square feet that two ton will have trouble keeping you cool if the temps in the summer get too extreme. You can never predict what the summer temps will bring. However you can have the equipment that will be able to handle what mother nature brings. If you are already spending the money you should spend money that is going to make you comfortable. Most home owners dont like to spend their money on HVAC equipment but have no problem buying a 3000 flat screen TV. Your money well spent would have been the bigger unit. Saving a little bit of money now isnt going to matter when it is 95 degrees outside for a month straight.

  7. #59
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,376
    Quote Originally Posted by tedkidd View Post
    They could be further narrowed by dropping the tstat setting a few degrees in advance of the weather events - kind of like gaining speed before going over a hill.

    On Monday when you see it's going to be 101f on Friday, move the thermostat from 75 to 72 and pull some BTU out of the house's mass.
    That is somewhat of a change from your more "steady state" thinking regarding tstat settings. To me, lowering the interior air temperature ahead of a 101 degree high temp day will only accelerate the rate of heat gain through the envelope, even before the daily high is reached. You may be "pulling BTUs out of the house mass", but you are also accelerating the rate at which those extracted BTUs are replenished to the envelope from outdoors. The greater delta that may exist between two states, the more force will be present seeking equilibrium.

    I am of increasing persuasion that the real mastery of "passive house" thermal envelope strategy is what I might deem "modulation of the thermal flywheel effect". IOW, in summer, for example, the house interior is not being blasted with heat gain even before peak solar loading occurs. Furthermore, by the time peak inward heat migration does occur, exterior conditions ate already setting up to slow or reverse the flow of heat through the envelope, such as night sky radiant cooling, etc.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  8. #60
    Join Date
    Jun 2012
    Location
    nampa idaho
    Posts
    66
    i like bryant myself but thats a ford chevy conversation in my opinion, they both do the job

  9. #61
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,428
    Quote Originally Posted by tedkidd View Post
    Lol

    Dan funny Dam.

    Hey, don't forget the ,,, ...
    with that said, I guess I won't be retiring after all .. Just changing careers ...
    Next opportunity ...
    bartending at MY Newly To_Be_opening chain of bars ..

    " SPORTS _ H V AC Talk? _ Open BAR "

    _ _ Come On In _ _
    ___________ Ventilation and Cooling provided 1 way or the other.
    ___________ at least the h_V_ac ... Venting will be very Well Practiced.

    ___________ _100% GUARANTEED_ TO BE REFRESHED!.!!
    ______+____ _ FREE BEER TOMORROW _
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

  10. #62
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,921

  11. #63
    Join Date
    Sep 2009
    Location
    Arnold mo
    Posts
    3,978
    Just inspected a home very similar to the OP's home, with the exception that the HVAC equipment & ducts are in a conditioned basement. He has a 3 &1/2 ton a/c that kept the home cool to t-stat set point of 75 even through this years heat wave. The home has excessive air leakage and is under-insulated.
    After air sealing, improving the insulation, and getting some shade on the west facing windows, I'm liking the 2 ton, 2 stage recommendation, but local HVAC contractor is recommending another 3.5 ton a/c. It's a shame that the biggest impediment to my helping homeowners make sound hvac choices is HVAC contractors.
    An answer without a question is meaningless.
    Information without understanding is useless.
    You can lead a horse to water............
    http://www.mohomeenergyaudits.com

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