Comfort and Airflow) Airflow Balancing

 

1. Understanding Equipment Capabilities

• Manufacturer's Literature and Data Plate:

  • Identify duct sizing and CFM requirements.
  • Note the external static pressure rating of the fan.
  • Determine the horsepower of the blower motor.
  • Consider space comfort conditions and control points.

• System Design Analysis:

  • Use gathered information to determine necessary adjustments.
  • Modify the system design to ensure it meets load conditions.

2. Preparing for an Air Test

• Building Walkthrough:

  • Locate registers, grills, equipment controls, and dampers.
  • Perform an inspection to determine and record all air distribution devices.

• Maintaining Constant Operating Conditions:

  • Set system controls to maintain consistent conditions throughout the test.
  • Evaluate proper fan operation, rotation, static pressure, and temperature levels.

• Test Ports:

  • Drill test ports on either side of the blower to measure temperature and static pressure.

3. Measuring Airflow

• Flow Capture Hood:

  • Measure airflow from each supply register.
  • Compare this measurement to the air volume flowing into the return grills to check for excessive duct leakage.

• Adjusting Airflow:

  • Compare actual measured airflow with design predictions.
  • Adjust the fan if the airflow CFM is higher or lower than required.
  • Adjust dampers to correct airflow in each branch of ductwork.
  • Balance other components as needed, starting at the furnace and working outward.

4. Annual Airflow Check or Post-Installation Testing

• Testing and Recording:

  • Supply and Return Air Temperatures: Record for both heating and cooling modes.
  • Manufacturer's Equipment Information: Compare rated temperature rise with test results.
  • Motor and Fan Data: Test and record full load motor amperage, voltage, RPM (using a tachometer), and static pressures.
  • Older Equipment: Record sheave pulley and belt size data.

• Adjustments:

  • Adjust sheaves to obtain proper RPM and air volume if necessary.

• Documentation:

  • Complete system report forms, including system diagrams, duct traverses, pulley data, and instrument calibration.
  • Include detailed information such as calibration dates to validate the test and balance activity.