Tjernlund M-4 4 Inch Metal Inline Duct Fan 200 CFM - High Performance HVAC Ventilation for Home, Basement, Grow Room & Commercial Use

Anyway, this blower does an outstanding job. It's not like the el-cheapo duct boosters that you get at the big box stores. This is solidly made and has a very high rating of 400+ cfm. That may not mean much to most normal people but to give you an idea, I added this guy to a single 15 foot flex duct of 6" diameter and I swear you can dry your hair under that register.Which gets me to the point that you REALLY need to consider whether you need this Mother of all Blowers or can settle with one of the smaller birdcage blowers. Being the geek that I am, I worked with a mechanical engineer to figure out duct back pressure, nominal cfms at each register, yadda, yadda, yadda. I figured that the real number for my blower is in the area of about 300 cfm so I was pretty sure that this would be overkill. Since the install is for the second floor, I figured the drop in back pressure would help the supply plenum to load up more efficiently. As it turns out, yes and no.This guy performs so well that adding it to a single 15 foot run/one register outlet is a waste...and it will blow napkins right off your table. So my final fix will be to add a 6" wye duct adapter to split the output to two registers. All these registers supply one great room so I'm not that concerned about balancing (at least for the HVAC season).I agree that the blower can be noisy but installing the blower as far from the register completely eliminates the noise, IMO. The noise at the register is due to high pressure air meeting poorly designed registers. This is perfect for my needs, it's TOO powerful. Always a good problem to have because you can fix that - you can't do anything but start over if the blower is wimpy.I also control this with the pneumatically driven duct switch that Tjernlund makes. Works perfectly, very simple. Finally, I also installed their birdcage blower downstairs in a duct that feeds the MBR. Very good quality, a nice bump in air delivery and stone cold quiet.As they say with blowers, one good tjern deserves another. I may pressure you into buying this but don't duct out and give your life a booster right now. OK, OK it's obvious I'm a big fan...