The MARD series damper is a power opened/closed, zone or bypass damper. It is usually used in light commercial applications on systems larger than 5 tons that do not exceed 2 in. W.C. at the damper, but may be used in any residential system as well.  The Modulating Automatic Round Damper is a round damper with a 24-Vac, floating-control type modulating motor for bypass and zone damper control. It is constructed of 22-gauge galvanized steel and has male (crimped) and female (uncrimped) ends to connect to any rigid or flexible round duct. The motor timing is 90 seconds open to closed.

The MARD is used for bypass control when connected to the Static Pressure Switch (SPC). Although it can be used on any bypass application, it is recommended for systems larger than 2000 cfm. The MARD can also be used as a zone control damper connected to a zone control panel.