| 1. | Greenheck Fan Ventilation Hood WD-400 Series User Guide rS GREENHECK WD 400 SERIES Non Motorized Backdraft Damper Horizontal or Vertical Mount Intake Application and Design The WD 400 series are non motorized backdraft dampers which may be mounted either vertically for intake air or mounted horizontally to allow vertical airflow down and prevent reverse airflow The dampers are opened by air pressure differential and closed by springs Optional motor packs are not available Ratings See page 2 for specific limitations Pr |
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