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  1. #1
    Join Date
    Mar 2005
    Posts
    67

    Building Static pressure

    I need to install a differential static pressure senser to control building static 1st part of my question, does the high pressure pitot tube go to the outside and low pressure pitot goes on the inside space. part 2 of my question, where is the most ideal location for the low and high pressure pitot tubes any direction would be great.......... THANKS

  2. #2
    Join Date
    Mar 2008
    Location
    NC
    Posts
    1,445
    High pressure tube should go inside the duct. Low is open to the space or ceiling plenum.
    2/3 down the duct (at least that's what all the literature will specify).

  3. #3
    Join Date
    Dec 2010
    Location
    Central US
    Posts
    387
    For building pressure control - Hi press to space and Lo press to outdoors setpoint is typically .05" WC. control parts houses typically supply a space pressure reference wall plate with a barb fitting for Lo side connection and an outdoor atmospheric referencer with barb fitting for Hi side connection.
    As far as best location it depends on the application. IE 2 story versus 1 story offices, lab, hospital etc.. need more info on app and Im sure we can help

  4. #4
    Join Date
    Mar 2008
    Location
    NC
    Posts
    1,445
    Sorry, was thinking vav. Try this link.


    http://hpac.com/ventilation-iaq/pres...mmercial-0210/

  5. #5
    Join Date
    Mar 2005
    Posts
    67
    Thanks for the response, it's a 2 story with about 40 vav's trying to keep space slightly positive, depending on time of year interier/exterier door's stay slightly open and as summer is approaching this seems to happen more often this time of year.

  6. #6
    Join Date
    Dec 2010
    Location
    Central US
    Posts
    387
    Quote Originally Posted by westendmechanical View Post
    Thanks for the response, it's a 2 story with about 40 vav's trying to keep space slightly positive, depending on time of year interier/exterier door's stay slightly open and as summer is approaching this seems to happen more often this time of year.
    Chilled water & hot water with AHU w/economizer, RTU w/economizer per floor & associated VAV's??

  7. #7
    Join Date
    Mar 2005
    Location
    Pacific Time Zone
    Posts
    4,151
    Osiyo - great points and I do set them to the lowest setting 0.1" wc, but most 'specs' I've come across seem to favor 0.5. I like the bi- directional setting for trending purposes. I agree once your below 0.0" wc it doesn't matter much if your sensor is sensing correctly. Sometimes the sensor is off just a bit or being affected adversely so I like to test slightly positive and slightly negative according to the sensor aka some simple cracked door and paper tests just to see if air is going in or out then. Another thing I've recently found it useful for is alarming. > -0.025 at one building the gals have a hard time opening doors. So alarm at < -0.02" wc if > 5 minutes. Long story but building under construction yet and too many holes and during certain construction activities we can't bring in any outside air. Let's just say my trends were extremely useful in proving out a design flaw and a construction exhaust problem.
    On another job, my first real 'learner' on wind effects we were able to find the correlation between consistent wind speeds above a certain value and the building going negative. That's the building I found the center of the flat roof to be the ideal sensing location. Ever since if I can get my outdoor reference to such a location I will.

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