Ring D for Blower Door Fan
Blower Door Fan Flow Ring D
Ring D is an optional flow ring for Model 3 & 4 Minneapolis Blower Door™ fans. Ring D measures air flows between 115 - 30 CFM. Ring D attaches inside Ring B by rotating the 6 fastener clips. When using Ring D, fan pressure is measured by using the pressure tap mounted directly on Ring D, rather than the tap on the top of the fan.
Please note that Ring D is required when using Ring E with the Minneapolis Blower Door™ fan.