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Thread: T.D Delta T

  1. #1
    Join Date
    Mar 2011
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    T.D Delta T

    Hi All

    Student here just leaning his way i was reading in about T.D i understand it;s the diffidence between the coil & space temp & how it determinants humidity.

    but looking a gauges say the A.C stat is set to 24c so room temp is 24C the pressure on the gauges would be 15 bar 217 psi to get 50% humidity 9-12c (17-22% f) T,D if i deducted 12c from 24c= 12c 10.6 bar (153 psi) but i have noticed a lot of r410a lowside are rated at 10 bar max.
    and that the usual operating conditions are 110psi-125psi

    Hope you guy get what i mean i would really appreciate if any one could point me in the right direction.

  2. #2
    Brian_UK's Avatar
    Brian_UK is online now Moderator I am starting to push the Mods: of RE Site Moderator : and general nice guy
    Join Date
    Mar 2001
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    Re: T.D Delta T

    I don't quite see how you expect a refrigerant temperature to give a set humidity figure.

    Humidity or relative humidity is based on the relationship between wet and dry bulb temperatures.
    Brian - Newton Abbot, Devon, UK
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  3. #3
    Join Date
    Oct 2001
    Nottingham UK
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    Re: T.D Delta T

    Hi Todd

    If your indoor evaporator coil is at a lower temperature than the dew point of the air in the room, the water vapour in the air passing over the evaporator condenses. As the amount of moisture in the air in the room becomes less, the %RH is lowered.

    It is usual to have the evaporator temperature at least 6K lower than the space to promote the transfer of heat. The greater the TD between the evaporator and the space temp, the greater the moisture removal.

    Have a read up on these links and search 'Humidity' on Google
    Last edited by frank; 25-02-2014 at 09:14 AM. Reason: Typo
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