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  1. #14
    Join Date
    Feb 2010
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    In a boiler room
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    Quote Originally Posted by amd View Post
    A 2 story house can be cooled properly without zoning, provided that the duct system is well designed and a 2-3F difference is tolerable.
    Cooled yes. Or heated yes. A system can be designed to heat OR (not and) cool a 2 story house.

    A given house needs a lot more cooling on the 2nd floor in summer than it needs heating in the winter due to the fact that hot air rises.

    For best comfort you should always zone floors separately.

  2. #15
    Join Date
    Jun 2009
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    Albuquerque NM
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    About now I think the OP is probably wishing he hadn't asked the original question.

  3. #16
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    Sep 2002
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    Cooled yes. Or heated yes. A system can be designed to heat OR (not and) cool a 2 story house.
    The ductwork can be over-designed on the second floor and dampered down during the heating season. Seasonal balancing is a must.
    General public's attitude towards our energy predicament: "I reject the reality of finite resource depletion and substitute it with my own; energy is infinite, we just need an alternative storage medium to run the cars on. The economy can grow indefinitely - we just need to "green" everything! Technology is energy! Peak what?"

  4. #17
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    Feb 2010
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    In a boiler room
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    Quote Originally Posted by amd View Post
    The ductwork can be over-designed on the second floor and dampered down during the heating season. Seasonal balancing is a must.
    True.

  5. #18
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    Jun 2009
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    Albuquerque NM
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    Quote Originally Posted by amd View Post
    The ductwork can be over-designed on the second floor and dampered down during the heating season. Seasonal balancing is a must.
    Seasonal balancing could get a little tricky in the Denver area. They have large temperature swings from day to night like we do here, and it's even possible to require heating at night and cooling in the day. This is one reason I'd recommend a dual-fuel system for that area. For heating, the lower heat pump discharge temperatures and longer run times can give you a nice low, continuous heat and better circulation.

  6. #19
    Join Date
    Jun 2001
    Location
    Moore, Oklahoma, United States
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    4,434
    Some climates use a heat pump for upstairs and gas furnace downstairs.

  7. #20
    Join Date
    Sep 2002
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    ^That's probably to avoid dealing with gas in the attic.

    The best option is to not put equipment in the attic though.
    General public's attitude towards our energy predicament: "I reject the reality of finite resource depletion and substitute it with my own; energy is infinite, we just need an alternative storage medium to run the cars on. The economy can grow indefinitely - we just need to "green" everything! Technology is energy! Peak what?"

  8. #21
    Join Date
    Jul 2008
    Location
    Rochester NY
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    4,756
    Quote Originally Posted by amd View Post
    A 2 story house can be cooled properly without zoning, provided that the duct system is well designed and a 2-3F difference is tolerable.
    Properly sized multi stage equipment running near continuously in a tight, well built home will make all floors comfortable all the time. High and low returns in upstairs rooms will help insure this, make sure you have them. You may also need to close bedroom doors during extreme temperatures.

    Elegant design makes brute force approach unnecessary. If it were my home the one additional thing I'd do is size ductwork 1/2 to 1 ton larger than your 2 ton heat pump.
    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.

  9. #22
    Join Date
    Jul 2002
    Location
    Yuma, AZ
    Posts
    2,361
    • Two ton is probably all the home needs. Undersizing is RARE.
    • Comfort will always be compromised in a 2 story home unless you zone.
    • Two unit zoning is not the best solution. Forget the arguement that if one unit fails, you have another. If that ever happens, a hotel is a better, more economically wise solution.
    • Ducted Zoning on a single system is the way to go. The ductwork should be 25% larger than standard design.
    • Most contractors prefer 2 unit zoning because they do better financially and they don't really understand how to make more complex duct systems work.
    • As usual, the results depend on the contractor, not the manufacturers.
    "I have never let my schooling interfere with my education."
    Mark Twain
    More at: http://www.quotationspage.com/subjects/education/

  10. #23
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    6,379
    EXCELLENT Advice throughout this thread.

    My house would be two 1.5 ton heat pumps.

    SIMPLE and most Reliable.

    How much, if any, would Denver [ mile high city ] "light" air impact selection and performance?
    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

  11. #24
    Join Date
    Apr 2007
    Location
    Saint Augustine, Florida, United States
    Posts
    1,163
    Around here, production builders are not using anyone other then production installation co.'s that just want to throw that system in. Usually about impossible to get them to do a great duct job. Bypass dampers in backward. Long flex runs with little distribution boxes, almost never ductboard plenumns or any metal duct. Difficult to get changes made to the plans, because all the bidding is done through Prod Builder. The zone systems I see regularly would be ripped apart if I posted pics here.

  12. #25
    Join Date
    Jul 2002
    Location
    Yuma, AZ
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    2,361
    Quote Originally Posted by JWB View Post
    Around here, production builders are not using anyone other then production installation co.'s that just want to throw that system in. Usually about impossible to get them to do a great duct job. Bypass dampers in backward. Long flex runs with little distribution boxes, almost never ductboard plenumns or any metal duct. Difficult to get changes made to the plans, because all the bidding is done through Prod Builder. The zone systems I see regularly would be ripped apart if I posted pics here.
    SO TRUE. About the only thing that you can count on is that the unit will not be undersized. Production installation companies rely on oversizing to cover thier own sins. Production homes leave comfort out of the equation. The duct system is really the comfort system in the home as the duct design and construction determines the distribution of the cooling and heating air. Show me a real estate contract that defines and guarantees any level of comfort. Maybe, "somewhere over the rainbow"....
    "I have never let my schooling interfere with my education."
    Mark Twain
    More at: http://www.quotationspage.com/subjects/education/

  13. #26
    Join Date
    May 2000
    Location
    Rochester, NY, USA
    Posts
    14,416
    Im just going to throw my in here.

    I have done RNC for 20+ years, mostly custom homes from 2200ft² to 7000ft². Did a lot of tract homes to.

    A 2300 ft² home can easily be done with one system. But someone has to do the math to get the proper air flow to the furthest register from the furnace/air handler. The key to most two story homes is the return air from the second floor. If you can get the proper return air you'll be fine. Hi/lo returns are the best, it's what I did in every home. I put individual returns in each room. NEVER-EVER use a central return air...they don't work nearly as well as individual returns. anywhere you can get a double return air (6x30)do it.

    Here's the deal: IF this home is 2x6 construction, with very good windows (low-e ) with above code insulation in the attic a 2 ton should be able to handle this home with no problem.

    I have never had an air flow issue, never even had a "it's drafty" issue.

    so this can be done, but the installing company better know what their doing

    as a side note:In this area (your market maybe different) there is no way your going to get a builder to put two systems in a 2300ft² house unless the buyer demands it, and then the buyer is going to pay through the butt for it I have been doing this a long time, I know how builders think. Thats why I got out of RNC.
    LOVE has four letters

    So does BEER, DEER,GUNS AND FISH

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