MARD-series, round, 8-inch modulating 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-inch water closet (wc) at the damper, but may be used in any residential system as well. Uses 90-second open-to-closed motor. Can be used as a zone damper. ML6161 is replacement motor. Available in 6-, 7-, 8-, 9-, 10-, 12-, 14-, 16-, and 18-inch diameter sizes. Use with Static Pressure Control (SPC) for bypass applications.