The Manual Balancing Dampers (MBD) from Zonefirst are sometimes used with the barometric by pass dampers to add back pressure to the duct system and control the amount of bypass air. According to the company, often when the bypass is ducted directly into the return at the plenum, too much air is bypassed through a barometric damper. This can starve longer duct runs for air and cause the ZPS to activate cutting off the HVAC. The MBD provides the back pressure to ensure proper airflow reaches the far away zones and ensuring only excess air is bypassed. The MBD is what is referred to in ACCA’s New Manual Zr for zoning as a hand damper. It has an adjustable control and comes in 4-, 5-, 6-, 7-, 8-, 9-, 10-, 12-, 14-, 16-, and 20- inch sizes. It should be ordered as MBDdd.

Zonefirst

www.zonefirst.com | eProduct 183