Resideo ZD10X20TZ Damper 320734 701 The low wattage 24V coil minimizes The low wattage 24V coil minimizes electrical load on the transformer while providing the magnetic force necessary to shift the internal slide even under high head pressure conditions High Reliability: Synchronous motor drive with a spring return ensures the valve reverts to the closed position during power loss this rectangular zone damper is the preferred choice for contractors demanding precision air management and long term mechanical durability in residential and light commercial applications but the internal spring mechanism provides a mechanical return to the open position