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Thread: Dilution OSA

  1. #1
    Join Date
    May 2007
    Location
    Dry as a bone Tucson
    Posts
    4,026

    Dilution OSA

    It is that time of year here in Tucson when the humidity spikes from the monsoons rolling in. Usual ventilation rates are not noticeable till the temps climb to 110 or it rains. Then you have an office or classroom that is no longer comfortable at the 75 degree setting. Occupants change the setting usually to 73 if they are conservative or 59 if they dont really care.
    I know that a dedicated OSA unit would be ideal but in a few weeks everybody will forget about the temporary "hot and humid" spell and readjust their stats to 75.
    When the complaints start rolling in do you shut the dampers for a while or let them bump the stats down?
    Whats your spiel about IAQ and ASHRAE sound like?
    Some Talk, Some Do
    "keeping condensing pressures low and evaporator pressures high"
    Comfort is my goal
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  2. #2
    Join Date
    Jun 2004
    Location
    St Paul, minnesota
    Posts
    1,015

    Wink

    install CO2 sensors in the returns and humidity sensors in OSA intakes. So when outside humidity rises osa dampers proportionally close down and only open long enough if CO2 on the inside rises. Once the CO2 drops the dampers close again until osa humidity drops or inside co2 rises. can be setup with higher end stats or an automation system.

  3. #3
    Join Date
    Jul 2002
    Location
    Yuma, AZ
    Posts
    2,361
    Quote Originally Posted by superfittertech View Post
    install CO2 sensors in the returns and humidity sensors in OSA intakes. So when outside humidity rises osa dampers proportionally close down and only open long enough if CO2 on the inside rises. Once the CO2 drops the dampers close again until osa humidity drops or inside co2 rises. can be setup with higher end stats or an automation system.
    I agree with the CO2 sensor or sensors. If the fan is ON, the return location is great, otherwise it should be inside somewhere. In some situations several may be needed in parallel to open OSA only when needed...(which may sometimes be never, depending on occupancy and in and out traffic). This can save huge amounts of energy in all weather.

    I don't see a need for the humidity sensors. What am I missing? Are you thinking economizer? I am not.
    "I have never let my schooling interfere with my education."
    Mark Twain
    More at: http://www.quotationspage.com/subjects/education/

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