Maintain CFM set point
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  1. #1

    Maintain CFM set point

    HI,
    I was thinking on how this systems from EBM can increase or decrease the motor rpm due to maintain the cfm set point when the duct impedance increase or decrease.

    I saw that they are using a static pressure sensor but how they can manage the motor speed with the pressure?
    Thank you!

  2. #2
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,271
    Quote Originally Posted by Domia View Post
    HI,
    I was thinking on how this systems from EBM can increase or decrease the motor rpm due to maintain the cfm set point when the duct impedance increase or decrease.

    I saw that they are using a static pressure sensor but how they can manage the motor speed with the pressure?
    Thank you!
    I didn't watch the video, but can say that variable speed blower operation is done all the time by static pressure setpoint. The static pressure is measured by a transducer, which converts pressure to an analog electrical signal. A controller is then programmed to respond to this signal (the signal could be 4 to 20 milliamp or 0 to 10 volts DC) and send a similar signal to the variable frequency drive (VFD) which then ramps up or down according to what is needed to hold the static pressure setpoint.

    To maintain a consistent cubic feet per minute (CFM) setpoint would likely involve a different type of design than what I described above, which is commonly used for systems employing variable air volume boxes (VAV) in various zones throughout the building. With what I described above, the CFM will vary in order to maintain a constant static pressure.
    • 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.

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