Auxilliary external fan for dryer vent?

We have a new deck that attaches to the house and extends 18' outward. To eliminate the moist exhaust from discharging under the deck we used 4" galvanized stove pipe coming from the inside of the ledge board on the house all the way through the outside of the deck structure. We fit a flapping louver on the outside flush with the deck fascia board.
While this seems to work just fine, it seems our drying time has increased somewhat. Most likely this is due to the extended distance the air must be "pushed" to exhaust to the outside. Prior to installing this I checked the dryer manufacturer's site to calculate the maximum length of the exhaust and our total was well within the max.
So, my question is this: Has anyone every installed an auxilliary exhaust fan on the outer end of a dryer vent before? Does anyone know of a cylindrical fan that might fit into a 4" pipe? What would be ideal is a section of exhaust pipe containg a fan that could be retro fit on the end of this setup.
Anyone have any suggestions? Thanks for any ideas.
Bob
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Would have to be sealed motor and rated for temperature above that of the exiting air! Just a Thought?
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wrote:

of the suggestions shows a booster fan that can be mounted in the cellar BEFORE the vent exits to the outside long run. Also, the boat bilge blower is a good suggestion as well.
Thanks again for the great input.
Bob
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It is possible that the vent pipe is clogged with excessive lint. I suggest a cleaning. Also, the vent pipe is long enough and extends outside that the warm moist air from the dryer will likely condense inside of the pipe. That moisture will cause lint to get caught easily in the duct accelerating the clogging process. I suggest that you insulate the entire length of duct with duct wrap to stop the condensation.
John Grabowski http://www.mrelectrician.tv

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Hi Bob,
There are several 'booster' fans available for dryer vents, but they're pretty pricey and add one more potential problem to the system. I've never tried one, but if your vent duct is all smoothwall, an annual checkup and cleaning would probably be a lot less hassle and long term expense than a booster, IMHO. As long as you're still within the max recommended length, I wouldn't be too concerned if you clean it regularly, even though drying times will naturally increase a bit.
And you can do a pretty good job of cleaning with a 30' central vac hose and shopvac, working from the outside with the dryer running on 'no heat/fluff'. They also make 4" brushes for the job, though I've never had a need to use one (and have heard horror stories from fellow servicers about the brushes coming loose from their long flexible poles *inside* a long vent run! Yikes!)
These boosters can be purchased with a pressure switch that automatically starts them when the dryer runs. They cost around $200 prewired.
You can see a couple of these in the current Armstrong parts catalog (wholesale only) here:
http://www.wdarmstrong.com /
From this page, click 'online parts catalog', then enter 32 in the 'page jump' search box. The one at the bottom of the page is an isolated motor design, which means lint won't get to the motor (still can clog the fan blades, though).
Hope that's of help to you.
God bless, Dave Harnish Dave's Repair Service New Albany, PA www.DavesRepair.com snipped-for-privacy@sosbbs.com 570-363-2404
Free home appliance tips from a 32-year pro repair technician! Get your monthly email newsletter here: (Back issues now posted too!) www.DavesRepair.com
Nehemiah 9:6

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Hi,

How long is the vent now, and how many elbows have been used?
Could a new vent in a different direction be used?

Only vent fan that I am aware of... http://www.acmemiami.com/dryerjet.html jeff. Appliance Repair Aid http://www.applianceaid.com /
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If you're a little savvy with the electrons you may want to give some thought to using a bilge blower. They make them to fit a 4" tube, already have mounting brackets attached, and are designed not to light off fuel vapors, so I'd think they'd be fine around the lint as far as combustion goes. Plus they're only ~$25 (West Marine). Unfortunately, most boats run on a 12V or 24V DC electrical system, but a xformer could solve that.
Just my $.02
~Rob
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