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  1. #27
    Join Date
    Apr 2002
    Posts
    11,808
    The 'remove the damper' comment in the signature is for the benefit of one specific fan of mine in here.
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  2. #28
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    4,894
    Quote Originally Posted by Carnak View Post
    Less than a design day in the Caribbean, early in the morning.

    Partly Cloudy 88F
    Feels Like
    101F
    Updated Sep 9 08:00 a.m. Local Time
    UV Index: 1 Low
    Wind: CALM
    Humidity: 75%
    Pressure: 29.91 in.
    Dew Point: 79F
    Visibility: 6.2 miles

    Sweet Home Alabama
    Right Now for
    Mobile, AL
    Save this Location On The Spot Weather

    Partly Cloudy 77F
    Feels Like
    77F
    Updated Sep 9 08:25 a.m. CT
    UV Index: 1 Low
    Wind: From N at 7 mph
    Humidity: 77%
    Pressure: 30.08 in.
    Dew Point: 69F
    Visibility: 10.0 miles

    Looks like well below design conditions in Mobile but it is still early in the morning right now.

    I see dew points of as high as 81 here, however it pretty much hovers around 80 for a good six months of the year, day and night.
    We saw dew points in the 80's here in WI a few weeks ago.

    The mfg'er equipment engineers could engineer units for those high humidity climates, but the mfg'ers refuse to do it. Mfg'ers ought to optimally engineer for the ultra high humidity climate zones! I would!

    I believe the power companies put the squeeze on them to lower the amp draw on equipment to help reduce their peak-load power consumption problems & costs of builder large capacities. Reducing the heat-gain load on the buildings is a far better solution for all of us!

    The design engineering might be the reverse of the ultra high SEER equipment with he small compressor & the huge coils. Back in the early 1970's & 1960's, when I would replace those earlier OEM compressors', the OEM Btu/hr called for were higher than the condenser & evaporator's Btu/hr Ratings.

    They operated under moderately heavy loads with low suction pressures & temps, the high SEER units due to engineering physics, can't do that.

    Now, if you take that combination with fins optimize accordingly, & then size the equipment to achieve long run-time-cycles & optimal total run-time,it will flat suck the humidity out of the air under the toughest load conditions like a good performing dehumidifier.

    When properly sized, the two speed compressors' coupled with lower CFM's helping lower coil temps are helping re-mediate the humidity problems. The problem is that the ultra high SEER units have trouble under heavier load conditions keeping pressures down & the E-Coils as cold as I'd like them

    Also, do all you can to stop high humidity air infiltration. Balance the Return air from the rooms so you don't have rooms with excessive negative pressures which dramatically increases air infiltration.
    http://www.udarrell.com/air-conditio...tent-heat.html

  3. #29
    Join Date
    Apr 2002
    Posts
    11,808
    520 CFM a ton darrel, single stage, PSC motor, humid locale

    http://hvac-talk.com/vbb/showpost.ph...8&postcount=94

  4. #30
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,296
    Make the house contain its conditioned air better. If overnight everyone with a conventionally constructed house suddenly had an airtight seal between attic and house, the power companies might start griping they aren't moving enough watts through the meters. AND...the level of interior comfort satisfaction would increase remarkably.

  5. #31
    Join Date
    Jun 2001
    Location
    DFW
    Posts
    684
    There is more than one way to control humidity with several people on this board advocating their own method.

    When it comes to humidity control, the house and the hvac system are not separate entities. You have to consider both when trying to find the best method.

    If you have typical construction with average to high infiltration, your only choice may be adding a whole house dehumidifier. And for climates that actually have four seasons, it may still be the best answer.

    For the hot humid climates, as you get the infiltration under control, other options become available. Which one will work best for you will depend on the sensible load, the remaining infiltration, and how complex you are willing to go with your hvac equipment.

    For example, if you have an extremely tight house with low to moderate sensible load, Carnak's approach obviously works. If you have an extremely tight house with very low sensible load, a different approach may be called for. Very few people have either of those conditions. For them, shophound's advice about sealing between the attic and living space is the starting point towards lower energy bills and controlling humidity.

  6. #32
    Join Date
    Apr 2002
    Posts
    11,808
    The house has more of an impact than the system.

    It is not my approach, just the same methods recommended by ASHRAE, the Florida Solar Centre, building science etc.

  7. #33
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,760
    The first step in controling humidty, is deciding if you want to cure the problem, or the symptom. Or both.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  8. #34
    Join Date
    Apr 2002
    Posts
    11,808
    The first step in controlling humidity is to control how outside air moves inside and to properly condition it before it is introduced to the space.

    It is like wearing a condom, as opposed to getting a shot of penecillin

  9. #35
    Join Date
    Jun 2001
    Location
    DFW
    Posts
    684
    Quote Originally Posted by Carnak View Post
    The first step in controlling humidity is to control how outside air moves inside and to properly condition it before it is introduced to the space.

    It is like wearing a condom, as opposed to getting a shot of penecillin
    That sounds good in theory, but is harder for some of us to do in practice.

    Any time an exhuast fan or the dryer runs (unless you have a condensing dryer), you are bringing in outside air to replace the exhaust. You may be able to confine most of that input to a fresh air intake provided for just that.

    But, that outside air comes in whether the AC is running or not, and if the AC is not running, it doesn't get conditioned. For my house, the AC is not running about 75% of the time on a hot day, and much less on cooler days.

  10. #36
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,760
    Quote Originally Posted by Carnak View Post
    The first step in controlling humidity is to control how outside air moves inside and to properly condition it before it is introduced to the space.

    It is like wearing a condom, as opposed to getting a shot of penecillin
    LOL... An interesting way to phrase it.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  11. #37
    Join Date
    Jun 2004
    Location
    4H: Hot, Humid Houston H.O.
    Posts
    3,304
    >>We saw dew points in the 80's here in WI a few weeks ago.

    Could it be possible this is in error? I poked around Weather Underground and for Madison WI saw max dewpoint reported at 75 for the past month. Average dewpoint was 56.
    http://www.wunderground.com/history/...lyHistory.html
    Then tried Dubuque IA and 76.5 was reported, with an average of 56. Although I took the 1st reporting station available, probably an airport would be more reliable than most amateur stations.

    By contrast, Ellington Field in Galveston TX reports over the past month max 77 dewpoint, and an *average* of 73. You can find similar conditions from almost any reporting station. When we say "high dewpoints" in hot-humid climates, it refers to chronic conditions not a rare occurrence for the record books. We cannot open the windows at night and expect to cool off and dry out.

    Regards -- Pstu

  12. #38
    Join Date
    Apr 2002
    Posts
    11,808
    Quote Originally Posted by pstu View Post
    >>We saw dew points in the 80's here in WI a few weeks ago.

    Could it be possible this is in error? I poked around Weather Underground and for Madison WI saw max dewpoint reported at 75 for the past month. Average dewpoint was 56.
    http://www.wunderground.com/history/...lyHistory.html
    Then tried Dubuque IA and 76.5 was reported, with an average of 56. Although I took the 1st reporting station available, probably an airport would be more reliable than most amateur stations.

    By contrast, Ellington Field in Galveston TX reports over the past month max 77 dewpoint, and an *average* of 73. You can find similar conditions from almost any reporting station. When we say "high dewpoints" in hot-humid climates, it refers to chronic conditions not a rare occurrence for the record books. We cannot open the windows at night and cool off and dry out.

    Regards -- Pstu
    its probably similar to a person waking up its 90% RH because it is cold out, then when the outside temperature climbs by 20+ degrees they think it is 90 degrress and 90% RH outside, not realizing that RH plummets when temps rise.

  13. #39
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,296
    Quote Originally Posted by Carnak View Post
    The house has more of an impact than the system.
    Well said. To throw more system at a problem that could be mitigated by a better house envelope is becoming more of an expensive proposition with each passing day.

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