The Model 4200 Contra System has two Model 6000 Fans running in series but in opposite directions. Used primarily as a duct tester it can also be engaged to test larger enclosures when you add a Large Door Frame and high pressure cloth.
The Model 4200 runs two 1.5 hp fans in the contra mode where the fans are in series but create flow with contra rotating blades revolving in opposite directions. House testing fans fall off dramatically at 100 Pa and only blow about 100 CFM at 500 Pa whereas the 4200 Contra puts out 5,000 CFM at that pressure.
Ideal for research projects where high flow at high pressure is needed for testing building components such as wall sections, mockup, roofs, doors, windows or pressure vents. ISO standards where testing in both directions is required at 300 Pa is ideal for this Series.