TerraBloom ECMF-200, Quiet 8" Inline Duct Fan with 0-100% Variable Speed Controller, Air Tight Metal Casing, Energy Efficient EC Motor. HVAC, Growing and Exhaust Applications Blower for Large Spaces

Costs more than Vivisun but this one is built far better than vivosun and very quiet . takes significant amount of time and effort to install if you are installing this in a tight ductwork so better to spend the extra $$ on good quality booster fan that you don't have to touch it again.

I used this to boost the HVAC to a distant room that was poorly regulated. I removed the base and mounted it between two new end plates in a 8x12 rectangular duct. Tied the power to the fan control thermostat circuit via relay so any time the HVAC was on the aux blower would be also. I really like the speed control, allowed me to get just the right bonus flow to the distant room. It comes with a digital and a potentiometer (rotary) type of controller. I used the digital one. Both retain the setting between power cycles. I have it set to 3 (of 8) and can barely hear the blower, even when right under it. It has about a ~15 foot control cable and 6 foot power cord. it also comes with a short breakout control cable if you want to make your own controller, with a tachometer signal available, which I didn't need or use. My only concern is the 140F max temperature rating of this unit, but I don't think my heater will violate it.

Our hood fan doesn't exhaust smoke very well. The Kitchen usually fills with smoke and alarm goes off every time. This fan worked awesome at removing smoke. Setup takes 30 seconds. Might add a grease filter shortly.

I am an HVAC biz owner that used the 8” fan to feed two 6” branch ducts (with an 8” intake). I turned my customer’s unusable bonus room above their garage to the coldest room in the house when it was 95 degrees outside. That was at a 75% setting. Might have to turn it down a touch! With the manual control it will always come back on if there is a power outage or you can hook it into a timer or relay control. Fan was nice and quiet and seems very well designed. I cannot account for longevity as I installed it and left. Time will tell. Fan starts out slow and Ramps up - a nice feature. I was testing it on my kitchen counter when it arrived to see how it performed. When it first came on I thought “there is no way this is 700 cfm....then it ramped up and nearly blew everything off my counter and started skating across the granite. Yeah, that’ll do!

The speed is variable to pretty low RPM, and shuts off at the bottom end. The top speed moves a huge amount of air. The decibels are pretty low throughout the range. Quieter than a smaller different brand I bought prior.