Air Balance Constant Volume Air System



Air balance constant volume air system (low Pressure) speaks to what is and constant volume air system. This is the step by step procedure to accomplish such.

Low pressure systems can be very simple single zone systems with just a few outlets or complex systems serving many areas in buildings using reheat coils for zone control.

Check and note the following items on the supply and return fans.

  • Correct fan rotation.
  • Filter condition.
  • Cooling coil condition. Set the system up to operate with maximum return air and minimum outside air. The following preliminary data should be noted at the supply and return fans.
  • Fan and motor RPM.
  • Motor current and voltage.
  • Fan, coil and filter static pressures.
  • Nameplate data on fans and motors.
  • Motor sheave, fan pulley and belt sizes. Traverse the main supply duct and return duct to determine the CFM delivery of the fans to air air balance constant volume system.

    • Air Balance Constant Volume Procedure

    Adjust the supply and return fan CFM deliveries to approximately 5% above design.

    Traverse the main supply duct.

    Balance the main supply branches to design CFM.

    Make preliminary outlet readings and adjust the outlets to design flow. No adjustments should be made after the final set of readings.

    Balance the return air system.

    The following final data should be obtained at the supply and return fans.

  • Fan and motor RPM.
  • Motor current and voltagr.
  • Fan, coil and filter statics.
  • Motor sheave position.

    Check the following controls.

  • Economizer system - function, calibration and damper action.
  • High temperature limit shutoff - function and calibration.
  • Low temperature limit shutoff - function and calibration.

    Set all controls to their normal set points.

    Compile and submit the air balance report.


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