These galvanized steel units are specifically sized to handle residential, small offices and dedicated ventilation applications. Simplified residential Installation manuals are a good point of reference for installing the nominal 400-i BPE units. Typically, you would install these units with two fans that provide 50% to 75% of nominal cfm in airflow. At this 50% to 75% flow range, the BPE units typically operate at 80% to more than 90% thermal efficiency. The 400-i Series is slimmer than other units and will fit behind a drop ceiling nicely. The 650 Series is slightly larger and meets the needs of light commercial applications and classrooms of 25-30 students in an “On Demand” ventilation scenario.