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  1. #14
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    5 ton on a 2500sqft new construction home in CA? Yikes. With good windows and insullation, I'm thinking most like 3-4 ton, but you'll need a heat load calculation.

    Ideally, if feasible, the best set-up woudl be a 4 or possibly even a 3 ton 2 stage unit and split the upstairs and downstairs into 2 zones.

  2. #15
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    The lowest cost solution might be to just replace the outside condensor unit only with a smaller unit based on a proper load calculation. Having a 5 ton coil on a 4 ton unit is acceptable.

    No need to repalce the entire system IMO.

  3. #16
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,376
    Quote Originally Posted by motoguy128 View Post
    The lowest cost solution might be to just replace the outside condensor unit only with a smaller unit based on a proper load calculation. Having a 5 ton coil on a 4 ton unit is acceptable.
    I doubt that would solve the humidity issues. Most parts of California cool off pretty well at night, so the heat gain to the house can fall off substantially a few hours after sunset. Compared to where I live, when we were hitting 105-108 degrees for daily highs, it often would not drop below 100 until around 9 PM.

    OP stated it was a two story house. If the thermostat is on the first level (and I'm assuming there's only one system on this house) this problem alone is aggravated by two factors: summer reverse stack effect AND oversized equipment. The downstairs stays cool more readily due to thermal gradient characteristics of a two story house, meaning the system runs less, thinking there's not much load. The less the system runs, the less it can dehumidify. If the OP pushes the stat colder to get dehumidification, the first floor overcools and then feels clammy.

    A whole house dehumidifier might be an option in this case, but it would still leave the OP with an oversized HVAC system. That said, the dehumidifier may allow the occupants to live in higher room temperatures before cooling would be needed. It's just a shame he's in a corner like this.
    • 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.

  4. #17
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,637
    Lets start over instead of offering solutions before we find the problem.
    What is the inside temp/%RH?
    What is the outside dew point overnite?
    How many occupants?
    Overnite setting of the t-stat?
    On/Off minutes ofcycle time of the A/c?
    How much water is the a/c removing during day and at night?
    Keep all of the inside doors open as much as possible to provide indoor circulation with pressurization/depressurization.
    Extreme coastal climates in CA can have high enough dew points to require supplemental dehumidification. Also occasional wet cool weather may cause indoor humidity problems. When the outdoor dew points are <55^F, adequate fresh air ventilation will maintain reasonable indoor %RH. Keep in mind that occupants add a considerable amount of moisture to an unventilated space. All homes need an air change in 4-5 hours to purge indoor pollutants and renew oxygen. When the outdoor dew point is <50^F, fresh air reduces indoor %RH. When the outdoor dew point is +55^F, adequate fresh air ventilation plus the moisture from the occupants needs several lbs. per hour dehumidification. If the a/c is operating enough, no problem. When the a/c is not operating enough, supplemental dehumidification is needed to <50%RH.
    Give us the information requested and we will be able to give some intelligent solutions.
    Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  5. #18
    Join Date
    Aug 2011
    Posts
    568

    Confused

    Quote Originally Posted by teddy bear View Post
    Lets start over instead of offering solutions before we find the problem.
    What is the inside temp/%RH?
    What is the outside dew point overnite?
    How many occupants?
    Overnite setting of the t-stat?
    On/Off minutes ofcycle time of the A/c?
    How much water is the a/c removing during day and at night?
    Keep all of the inside doors open as much as possible to provide indoor circulation with pressurization/depressurization.
    Extreme coastal climates in CA can have high enough dew points to require supplemental dehumidification. Also occasional wet cool weather may cause indoor humidity problems. When the outdoor dew points are <55^F, adequate fresh air ventilation will maintain reasonable indoor %RH. Keep in mind that occupants add a considerable amount of moisture to an unventilated space. All homes need an air change in 4-5 hours to purge indoor pollutants and renew oxygen. When the outdoor dew point is <50^F, fresh air reduces indoor %RH. When the outdoor dew point is +55^F, adequate fresh air ventilation plus the moisture from the occupants needs several lbs. per hour dehumidification. If the a/c is operating enough, no problem. When the a/c is not operating enough, supplemental dehumidification is needed to <50%RH.
    Give us the information requested and we will be able to give some intelligent solutions.
    Regards TB
    hey,nice post, that's why you make the big bucks$ goOOO,RIPON,WIS!

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