Tjernlund M-4 Metal Inline Duct Fan, 200 CFM, 4"

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...

Our application is a little out of the ordinary and required a really heavy duty, well balanced turbine. Do not confuse this with the widely advertised duct fans that will not blow out a candle. This turbine will launch a sailboat. We created another victorian house solar heat system with over 100 feet of 8" duct work which needed a turbine that would A) run quiet, B) not vibrate, and C) move a lot of air. A) The noise from the fan is the air movement. There is virtually no mechanical noise from the unit. The system is in the attic turret and third floor space; it can not be heard on the second floor. B) To test the balance, we took the fan out of the box, placed it flat on the bench, and put power to it. As it spooled up to full speed, we were on all sides waiting to keep it from bouncing off the bench. Ran for about 2 minutes and did not move. C) Both on suction and pressure side it moves a tremendous amount of air. Comes with a power pigtail attached, and a sturdy mounting bracket. We mounted it on heavy rubber grommets with 3/8" bolts. One improvement that could be made would be a little wider flange for attaching duct work. A thin piece of self adhesive weather strip on the flange and then a sturdy hose clamp rather than an HVAC zip tie will keep the duct secure. A previous installation of this type required a rubber boot on both sides to keep the vibration out of the duct work. This unit is so well balanced, the duct work is directly mounted. For retrofitting exhaust fan applications, this unit will give you the option of mounting it a long way from the air source and still exchange the air adequately. As above, our application involves over 100 feet of 8" duct and it works perfectly. Also look into the Duo-Stat temperature/humidity control or the Woods Timer switches, they both work well with this fan. Manufacturer was very helpful with technical assistance and interest in our unique installation. Great turbine for many different applications!