Aprilaire 6912 - 12" Round Barometric Bypass Zone Damper
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Quick Product Overview:
Bypass Damper method: Allows the system designer to size the ductwork in the same manner as
a non-zoned application. The pressure relief is handled by use of a bypass damper directing
excess airflow back to the return or to a dump zone.
Determine bypass damper sizing: The purpose of the bypass damper is to maintain airflow
through the HVAC equipment when zone dampers close. Sizing the bypass damper is calculated
considering worst case scenario. Subtract the air flow of the smallest zone from the total system
airflow and the difference is how much air you need to bypass. (Total system CFM - Smallest
zone CFM = Amount of air to bypass). Then, refer to the bypass damper sizing chart for the right
size bypass damper.
Positives: Utilizes existing duct design methods; good retrofit option.
Negatives: Potential of bypassed air conditioning the return or dump zone; requires plenum
temperature control (included with Aprilaire zone panels).