There are few books that explain airflow proportion balance on supply outlets. Balancing airflow thru out
a building takes lots of time and practice. A design airflow is given for each individual air device and a
balancing damper is used to decrease the airflow on outlets that are over there design flow. Closing down
high volume grilles will increase or push airflow to other outlets that are low on airflow. The tricky part
is getting that airflow to go were you want it to without increasing those grilles you have already turned
down. Many things can influence airflow travel through a duct. Airflow will always take the easiest path,
however the easiest path does not always leave a proportioned grille balance. That is why dampers are
installed. When using dampers you should always use branch and zone dampers first. When all your duct
branches have design airflow then you would use grille dampers. The following list are things that should
be considered when doing a unit system grille balance:
- Make sure all branch, zone, and grille dampers are in the open position.
- Set the total airflow on the Air Handler Unit.
- Measure all outlets before making any airflow adjustments.
- Compair your grille readings with your unit traverse to get a duct leakage percentage.
- Use branch and zone dampers if provided to set flow through all main ducts.
- Balance each outlet, and take a final reading.
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