Not sure if my issue is due to lint/dust or vertical orientation.

This fan is great, that is it is relatively quiet for the high flow of air it creates.

I installed this into the ceiling above my washer and dryer, vertically. I use this fan as a whole house fan (900 sq ft condo). The crawl space above the laundry room vents to a 12" vent on my flat roof. So I use this fan to suck the air from the living space, push it into the crawl space, cooling the crawlspace and cooling the living space. With this method, I can generally keep it 3 deg cooler inside than outside. As I am fairly comfortable with air moving up to 83 inside, it is only on days where it is over 86, when I am hot, that I need to turn on the air conditioning.

This whole house fan I figured out uses about 1 kwh per day ($0.20 per day cost) to run constantly, although I have it on a thermostat that only turns on if the temp inside my condo gets to about 76 deg. In a very hot month, I'd guess it runs 50% duty cycle ... so the cost is about $3 for the month. Saving me $80-100 in that month on air-conditioning.

The bad:
This unit ran flawlessly for the first 4 months maybe, then it started rattling, getting noisier. After a while I decided to take the fan motor and blade out of the enclosure and have a look. The bottom (intake side) has a cup the axle rests in, this cup is lubricated. I think this type of setup is made to be horizontally mounted. In my vertical mount, dust falls into this cup and mixes with the lubricant causing friction, and eventually noise. At first I cleaned the axle cup with qtips and alcohol then lubricated with silicone lubricant. This lasted for a couple months, then loud rattling again. I asked my dad (mechanical engineer and mechanic) for his advise, he told me to use motor oil. I cleaned the cup with qtips and alcohol again (alot of residue from the silicone lubricant), and put about 5 drops of motor oil in it. This has made the fan quieter than I ever remember it being. It has been 2 weeks of running but not many hot days so maybe only 20 hours or so of running. I will continue to post in a couple months how this motor oil lube has kept it quiet, or needs maintenance every x months.

update, 5 months with motor oil as lube, great, no change, still quieter than it was out of the box, updating from 3 to 4 stars

installed the fan about 3 weeks ago... The Fan started out pretty much as expected and was working well for what I needed it to do.. then the screw that holds the fan blade on came loose sending the unit out of balance and it started making one heck of a lot of noise.. I attempted to tighten the fan blades but I can't seem to get it adjusted properly... So I ordered a different fan from a different company just now...

I read another review where someone said some of the mounting screws came loose... seems like this company should start using some locktite or something to keep things secured in a product that's expected to vibrate..

Good , powerful and not too loud ( update: one is very loud now) , served my needs really good, no complaints yet, will see how it will hold

update : knocked off one star - its 1/4" smaller than 8", standard 8" duct wont fit in not crimped end
another update - one more star off - one fan is sounds like airplane is taking off after light use for 3 month

This item does not fit onto standard USA 8" DIA heating duct pipe. The item's diameter is closer to 7-5/8". What I found could be done after cutting a key-way slot about 4" X 1/2 wide" into a standard section of 8" duct (to accommodate the fan's power cord) is installing the fan INSIDE the 8" duct. A piece of duct tape (real duct tape - aluminum with a sticky backing) covers the slot and temporarily helps hold the fan in place. Then added a couple of stainless steel duct screws to the fixture after the whole replacement assembly was roughed in and tested.

The fan failed after about 100 hours usage over 10 months. It had a slight vibration which fatigued the fan blade and it cracked through the aluminum blade and two blades came off. At some point the motor thermal protector activated and now the motor is dead so we cannot replace the blade... The fan is listed at 400 CFM but this is the maximum in boost mode. For free air use the flow is probably around 180 CFM. I'm trying a Suncourt DB208P and we'll see if it lasts any longer...