Dryer Vent Booster Fan

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mrb627

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Joined
Sep 12, 2001
Messages
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Location
Buford, GA
Well, I made the decision this week to purchase and install a dryer vent booster fan. Ordered via Amazon. Will post detailed installation steps when the unit arrives.

Malcolm
 
I'm not familiar with your situation, but I've always felt that booster fans are a "last resort" kind of thing.

If there is enough static pressure drop in your duct system to cause problems, it would probably be better to correct the cause(s) of the pressure drop than to add a fan to fight the problem...
 
Years ago, on eBay, I bought two filter boxes that were made to go in front of a suction fan for a dryer. I use them on one of the indoor-vented electric dryers that I use in the winter. Even with the second lint screen in the boxes, I have nylon hoisery clamped on the discharge tube and there is still lint that it catches.

I used the dryers for the first time this fall yesterday after lows in the 40s and highs in the low 50s with no sun.
 
The dryers in my college dorm building had boosters, but only because the pipes travel a little more distance than normal.
 
Multi-family and commercial buildings are a little different story - multiple dryers feeding into a plenum, longer runs to daylight and so on. Those vent systems tend to be designed by mechanical engineers that know what they're doing, taking static pressure and code requirements into account, among other things.
 
Nice video, BUT

Their demo fails to take into account the most important factor in lint adhesion: the steamy dryer exhaust. While I can't be sure about the fineness of the lint they dumped into the test chambers, fine lint readily adheres to moist surfaces and believe me, dryer exhaust runs get moist. The major exception is the venting from an old WP perforated back cylinder dryer. Enough air passed behind the drum that there was always enough hot dry air going through the venting to keep the condensation in the pipes low. My frankendryer with the 37.5K BTU burner runs at a steady 165F and it boils the moisture out of the load so fast that the brick area in front of the vent hose is wet with condensation, even on hot summer days.
 
Vent Kit Arrived

The vent kit has arrived. A week ahead of the expected time frame. I'll need to investigate what I will need to get this thing installed this weekend. I'll post some pix, if I can.

Malcolm
 
Another Shot

Installation was pretty straight forward. Had to build a base for it. Had to run an electrical outlet too. All in all, not too bad, except for the balancing act between rafters...

Malcolm

mrb627++10-15-2012-07-02-17.jpg
 
Airflow.

You could really hear the air being forced out of the vent outside. The dogs sat out in the yard and looked up at the vent during my test run.

Also, inside when the dryer would pause to reverse the drum rotation, you could hear the suction being pulled through it.

Don't think I will ever have to worry about cleaning the exhaust line again.

Malcolm
 
Faster Drying

Well, I only had time to process a couple loads of laundry yesterday. And as far as I can tell, I have shaved about 20% off the total drying cycle. I will do some further testing next weekend.

Malcolm
 
Great job Malcolm!
Do you have a switch that turns the fan on, or is it automatic when you start the dryer?
One of my dryers has a very long vent run and I am thinking about trying this out.
Thanks for the pictures.
Brent
 
Pressure Activated

The fan is pressure activated. When the dryer starts, the fan starts.

Although I do have a wall switch in the garage that will cycle power to it, if necessary.

( wish I had done this years ago )

Malcolm
 
Looks good! Mine goes through the attic too. How long is your total run? I think mine is like 15 to 18 feet from what I can tell with two small bends along the run.
 
Fan performance.

Well, I made it through the weekend and did an enormous amount of laundry to help evaluate the booster fan performance. All in all, the amount of time it takes to dry a load of clothing averages about 20% reduction.

I feel that the fan would perform better if I were using an American style dryer instead of the Miele. The Miele dryer that I have doesn't always produce enough airflow to engage the booster fan. As a result, the dryer may run for several minutes before the fan spins up.

When the fan does power up, there is a ridiculous amount of air pulled through the dryer. Bottom line, I am satisfied that the fan does what it promised to do. And if I don't have to clean out the duct work twice a year, then it was worth the money.

Malcolm
 
Long Dryer Vents

Thanks for sharing your experiences with the booster blower for your dryer Malcolm.

 

I have found that compact American and all European 24" dryers should NEVER be used with a vent system longer than 6 or 8 feet and two elbows. Anything longer that this requires some sort of booster or just inside venting with good additional ventilation used in the area where the dryer is located.
 
Great idea - good device choice - never knew about this - why I like AW.org. I 've never seen a dryer vent run of more than 6-8 feet, at the most. If you're shaving off 20%, and your Miele was running 30 -40 minutes or more each time you did loads of wash, that helps on the annual electrical. Good job!
 
@ovrphil:

There is a difference between physical length and effective length of duct run. The difference is important.

Most people don't need a dryer duct booster fan, unless there's a problem with the original house design or construction.
 
Malcom: But, it brought to mind...a long time friend's father, a chief mechanical engineer, whose firm designed the Saturn V rocket cooling system(the system that sprayed water on the engines to prevent meltdown of launch structure)... passively mentioned math and physics relative to his work - kind of entertaining, too( Bernoulli principle, thermal dynamics, etc.) He's gone now, but your mentioning of "effective length" reminded me of him and it led me to a link(read about half).....thankfully, most don't need a fan..or that link! ...but it's good to see someone using their engineering skills here...never know, one day that idea might be useful to me/anyone. :-) [this post was last edited: 10/25/2012-07:43]

http://www.achrnews.com/articles/minimizing-system-effect
 
Notice one pipe (booster inlet?) is corrugated and the other is smooth. That makes a HUGE difference in flow resistance. Had the entire pipe been smooth the booster may not have been needed.

I had a high-flow vacuum device (broadcast industry) with very noisy vacuum pumps. The vendor said the pumps could not be remoted. They had tried it with the same corrugated hoses used within the machine and it definitely did not work. I used food processor hose, same size only smooth inside, moved the pumps to an adjacent utility room. Worked fine and a lot less noise fatigue for the guys in the room with the machine.
 
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