The ND Series Of Ultra-Zone Dampers Was Designed with The Installer and Homeowner In Mind. This Damper Is Easy To Install and Easy To Checkout. The Led Display Allows The Installer To Visually Check The Damper Operation. With A Sturdier Frame, The Damper Installs In The Duct Much Faster and Easier and The Nylon Bushings Insure Quieter Operation. This Is A Feature That Homeowners Will Never Hear About! Quieter Operation and A Longer Life Motor Equals No Call Backs. The Motor For The ND Damper Is Driven By 17 In. Lbs. Of Torque, Possesses A Manual Gear Release, 3 Wire Power Open/Power Closed Operation and Fail-Safe Led's For Quick Diagnostic Checks. The Motor Is UL Listed and NEMA Class 2 Certified. The Easy Access, Quick Connecting Terminal Block Eliminates The Need For Wire Nuts and Allows For Trouble Free Use. The ND Damper Has A 97% Leak Proof Rating. Overlapping Blades and A Strong Positive Off Motor Insures Accurate Control Of All Zones.The ND Dampers Combined with The Ultra-Zone Zoning System Provides The Most Comfortable and Reliable System In The Industry.