See attachments on how to properly diagnose Arzel dampers and pumps.

This is from one of the Arzel Techs:

Most conventional HVAC systems shouldn’t exceed an ESP of 0.30 when the ductwork is zoned with the smallest zone calling by itself; design if all zones are open should operate around 0.08-0.10 ESP.

Our dampers will operate in higher pressures, I’ve had them in our lab sealing properly against 0.40 ESP;

Our round dampers with the smaller blade sizes will seal against higher pressures than that since they are frequently used in SDHV application that run up to 0.50 ESP.