Tjernlund M-4 Metal Inline Duct Booster Fan for Ventilation, 4 in, 200 CFM | 4 in metal inline duct booster fan delivers up to 200 CFM for compatible ventilation systems; verify duct and electrical fit.

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!

I recently installed a new register in my family room open area. This area had an imbalance of 4 degrees from the sleeping areas. The company that installed the new register used flexible duct for the run. With 50 feet of flexible duct (not the best in transferring air) compounded with having to snake that duct around several columns, the result was a disaster. The area increased by 1 whopping degree! So my next solution to the problem was to install a regular 240 CFM inline fan. Due to having not enough room, the fan was installed near the start of the duct run. It's not the most ideal location but that was the only choice I had. Well, suffice it to say, the result was a disaster (again). The fan had no effect on the air pressure whatsoever! Why is it that adding a 240 CFM gave me no improvements? Hmm... At the end of my wits, I turned to the stronger centrifugal fans. There is this Tjernlund rated at 530 CFM and clones at 400 CFM. Needing as much air as possible, I chose the Tjernlund. Moreover, Tjernlund has a manufacturer website and instructions for the installation. Its not a difficult wiring job, but it's nice to know that a manufacturer support its products with instructions! Well, what can I say? The result was not a disaster! For whatever reason, this 530 CFM fan pushed so much air that the register pressure felt about 5-8 times stronger than the 240 CFM fan which might as well been no fan at all. So to summarize, this fan pushes 5-8x more air than the other inline fan but is only rated at 2.2x the CFM. Something is wrong and someone is lying on their stats! Since this fan was installed in the crawl space, the noise didn't bother me at all. It was about as noisy as the 240 CFM inline fan so it's actually not that loud. However, it's not quiet because air being moved around cannot be silent. I also didn't use a speed control as I needed as much force as possible. However, for short runs, this fan may be overkill without a speed control. Also, I took out the outlet plug that came with it and wired it straight to the auxiliary output on my Trane HVAC. This allowed the fan to turn on and off by call only and not stay on all the time. You do not need pressure monitor if you can hook it up to your HVAC fan control It's not often that a product works as advertised! Highly recommended!

Very good fan. I use it to pull air from my basement and pass it around my sealed combustion fireplace to heat the house more efficiently (removed the weak 150 cfm squirrel cage fan that came with the fireplace). I also created a damper "by-pass" so I can easily reverse the air flow and heat my basement using the same duct system without having to flip the fan around (BTW, the fan is not electrically reversible). Air flow/suction is excellent. Noise level is acceptable if insulated kevlar flex ducts are used (metal ducts transfer noise more readily). I have a speed control installed, but I seldom use it as I like to have the fan on high to utilize its full potential (that's why I purchased the 6" fan versus the 4" fan). This is my second M-6 fan ( the first one had an impeller problem). The first fan developed the same "wobble noise" as another buyer stated. I had the fan installed for a couple years when it developed the problem. I took the housing off and noted the fan/impeller blades were attached to the "cage" with full plastic on one side and plastic "studs" on the other attached to a metal crown. The small studs (made of plastic melded onto the metal crown) appeared not to be properly anchored and allowed one of the plastic blades to eventually bend and push against the fan housing causing the wobble/noise problem. I tried to straighten the blade and re-anchor it to the cage. So far so good (about 1 year in with the fix) There is a noticeable, but slight, vibration probably from an out-of-balance situation. I just purchased another Tjernlund M-6 fan from Amazon (of course the price was great and free shipping). I looked into the impeller and it appears the entire unit (blades and cage) are all plastic which will eliminate the "plastic stud" separation problem I had. Maybe the company had a problem with the original design and corrected it. My original unit is still functional and is destined to become a garage exhaust fan. Anyway, for less than $90 this fan performs very well even when utilizing several elbows in the line. According to the manufacturer it can handle air temperatures of up to 140 degrees F. I pushed 130 degrees through the unit for hours day-after-day with no problems to the motor, housing, or bearings.

WARNING FIRST: This ships with a cardboard collar inserted on the intake side. It was VERY wedged in there on my fan. So much so that I wasn't sure if it was a piece left over from the manufacturing process that got missed. It was reference NOWHERE in the instructions or on line. I had to wait until the next day to reach them and ask about it. Turns out I would have done no harm in TUGGING on it to get it out. So all ended well after all. But if you are considering buying, just know that so you don't lose a day. ON TO THE FAN: This is an excellent fan. I installed it to go through a rim joist to vent a corner of my basement into the space under the front porch. So final picture: Outside the house is the metal outlet cover and its end-cap with the flappy bit to keep bugs out when the fan is off (purchased separately). I pushed it through the hole and into my basement. That gave me about a foot inside of the 16 inches or so of ducting attached to the cap. I slipped the fan over it and screwed the fan to the side of the nearest floor joist. That set up sucked a LOT of air. But it was pretty loud. So I decided I would live with it, but then went on to testing the bits of ducting and flapper valves and what-not on the intake end of it (since it was there!) just to get an idea of how things fit (intake is smaller than outlet). And lo and behold! I grabbed a piece of 4" duct splice (just an 8-inch long piece of ducting made to splice 2 normal lengths/diameters together) and slipped it on. It was a bit of a loose fit, but some blue painter's tape made for an adequate seal (ability to undo is greater than aesthetics up in a back corner of my basement!). Now for the kicker: That little 8" piece of duct made all the difference in the world to the sound! It had a huge muffler effect. I'm guessing the loudness of the original sound really was about the sound of the air being beaten around by the internal impellers. This reduced it to mostly just the sound of air rushing in. I probably cut the noise in half or better. So tip to ya!

I installed this booster fan in the main square duct (had to make a sheet metal transition) that supplies the entire 2nd floor of my 2 story house. Air handler is in the basement and did not have enough power to supply enough airflow to the upper floor where all the bedrooms are. Took me 8 years of trying other "solutions" to the problem until I finally got the guts to cut a hole in my wall and install this fan. Until recently I didn't even know they made booster fans this powerful! This fan completely solved my airflow problems!!! Now I am able to cool off the bedrooms with ease. Absolutely the best money I've ever spent. I wired an outlet inside the space where the fan is installed and wired a switching relay to turn the outlet off and on with the main air handler fan. Relay cost me 12 bucks and the outlet cost me about 5 bucks if I remember correctly. Not difficult to do, just get help from an electrician or someone knowledgeable on home wiring. This fan has been installed now for about 2 weeks and is working perfectly. I used some rubber vibration dampers that I had laying around from an older washing machine, I drilled a hole through the dampers and put them between the mounts of the fan and the studs inside the wall where I mounted the fan. Vibration is very low, noise is very low. No HVAC professionals would give me any options of how to fix my airflow problems except to buy a second air handler (thousands of dollars) to provide air to the upstairs. Nope, this fan will do!

Using this to move air to my second floor from the first floor to avoid installing a second HVAC unit upstairs. Working great so far. Pros: -Exhaust end is VERY quiet once you put flex duct on it, and the intake end is also quiet with the same flex duct -No vibrations at full speed -Moves loads of air -Doesn't slide around even without being bolted down Cons: -Short cord, roughly 5-6ft -Intake end is a little noisy after installing an air filter at the return grille -Intake flange is so short that I'm afraid the foil tape might break loose and rip the flex duct apart as it's sucked in, but the zipties seem to be holding up well -Exhaust flange is short and TAPERED which makes it very difficult to attach anything to it with foil tape and zipties. It wants to blow the flex duct right off of it. This end would be better suited for metal duct that's been attached with screws in the current design. It would be much better if it were not tapered, and enlongated to 4 inches. I was afraid to bolt it into the wood because of a resonating effect. There's a huge difference in noise between holding it up and placing it on the floor. I cut maybe 70% of the noise just by placing it on a piece of scrap carpet, and at the same time, it's not moving anywhere. I marked the floor to be sure. No change in position after 24 hours. I used a fan speed controller to tone it down by about 20% - full speed was too much for my 12"x12" register vent. Poor thing was shaking and whistling like a runaway train.

Move a lot of air, works good. But it is very noisy

Excellent for moving air out of a crawl space. a little louder than I would have wanted but does the job magnificently. the one I received had two rail mounting feet which made it a whiz to install.

Fan works very well. I used 6 inch galvanized duct pipe for smooth air flow. The weight of the pipe will twist the housing and cause the fan blade to rub on the housing and make a noise. I used steel pipe strapping 1 Ft. each side of the fan to support the intake and exhaust pipe and have no fan noise The fan is very quiet for the amount of air it is moving about the same DB as a the average bathroom vent fan. We have it installed just off the kitchen as a booster for the stove range hood. We can now pan sear steaks with out the smoke alarm going off.

this is the best fan I bought. quiet and powerful. but now it is 50$ more..

Todo muy bien Muy buen material y muy bien precio

Decent quality at low price.