Dryer Booster fans ?

Discussion in 'HVAC Heating & Cooling' started by Agu, Jul 17, 2009.

  1. Agu

    Agu New Member

    Messages:
    66
    Location:
    Tampa, FL
    My dryer runs forever, gets hot and takes two cycles to dry clothes, and that's with a new clothes dryer. (Electric dryer if that's an issue)

    I suspect it's because the 4" dryer vent is 25' long with 5 elbows. I've upgraded the dryer and checked the ductwork for obstructions (none) with no improvement.

    Two options I've looked at are,

    1) Tearing out the bathtub in the guest bathroom and installing the washer/dryer in that space. I'd end up with about 4' of dryer vent in that scenario. The Mrs isn't real thrilled with this idea even though I told her the old laundry room would have enough space for a whirlpool tub and shower. (and the plumbing is already in place :D )

    2) Installing a booster fan on the vent (most likely scenario).

    Will a booster fan work? Any brands recommended if they work as advertised ?
  2. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    A vent booster will do wonders for you. FanTech makes nice ones. They have an air flow switch on them, so they turn on and off automatically as the dryer runs.

    You might save the cost of the booster fan within a year or so, on the reduced gas and/or electric bill, from the dryer not running nearly so long.
  3. Agu

    Agu New Member

    Messages:
    66
    Location:
    Tampa, FL
    I've been looking at Fantech, just wanted an unbiased opinion.

    Now I'll have to get up at 6am on my day off to do the install before the attic heats up.
  4. FloridaOrange

    FloridaOrange Plumbing Designer

    Messages:
    1,317
    Location:
    SW Florida
    Have you had the vent line cleaned? A vent full of lint will create all those symtoms even with a new dryer and maybe especially with a new dryer.
  5. Agu

    Agu New Member

    Messages:
    66
    Location:
    Tampa, FL
    As posted, I checked and cleaned the vent line. There was minimal buildup over the 25' with 5 elbows.
  6. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego

    Yes, I believe if you check the dryer manufacturer's install spec, the 5 elbows on 25' probably puts you over the recommended. Air flow is the key to drying. With enough air flow, you could run a load of clothes with the heat off, and they would dry in time. No matter how hot the dryer heat is, without goo air flow, drying time is adversly affected in a big way.
  7. patsfan78

    patsfan78 Web Development | HVAC

    Messages:
    33
    Location:
    Maine
    Anyway to shorten

    Is there anyway to shorten the distance between the dryer and the outdoor vent? 25' plus 5 elbows is a lot. And most likely well over the recommended manufacturers distance. Elbows are most likely the equivalent of 2'-3' of pipe.

    See if you can more the outdoor vent.

    good luck,

    http://www.hitechheat.com
  8. Agu

    Agu New Member

    Messages:
    66
    Location:
    Tampa, FL
    Laundry room is in the middle of the house. Rerouting the horizontal line would only reduce the run by about 5' in the best case scenario.
  9. Thatguy

    Thatguy Homeowner

    Messages:
    1,460
    Location:
    MD
    run some numbers and checks first

    I'd do some calculations first so you can select an appropriate booster fan; the dryer manuf. might have the formulas.

    Or you could temporarily vent the dryer to the room [with all windows open] and see if the drying time improves.

    Also check that the voltage & current consumption is within spec's. Mine takes 24A @ 240v.
  10. Agu

    Agu New Member

    Messages:
    66
    Location:
    Tampa, FL
    Some follow up to this thread. Got the dryer fan DBF 110 and auxillary lint trap because the fan is within 15" of the dryer. Had to put the fan in the laundry room because I didn't want possible condensation dripping out of the fan in horizontal ductwork onto a finished ceiling. ( Also there were code issues with installing the booster fan in the attic that I didn't want to deal with.) The dryer fan works as advertised, drying time has dropped by 50% to 70% depending on the load.

    Too bad a moron designed the lint trap. It opens/closes with spring clips. The Mrs can't get it opened to remove the lint screen. I usually do the laundry so that's not a huge issue. (Please don't revoke my "Mancard " ;) ) In addition, lint drops on the dryer, floor and any clean laundry within reach every time the lint trap is cleaned.
  11. ballvalve

    ballvalve General Engineering Contractor

    Messages:
    3,261
    Location:
    northfork, california
    No inspector would have allowed that installation around here. Seems to me the lint trap at the dryer should be adequate, and the "hidden" one a recipe for disaster.
  12. Agu

    Agu New Member

    Messages:
    66
    Location:
    Tampa, FL
    Uhh the auxillary lint trap is in the laundry room about three feet above the the dryer and both fully accessible and within code. And No, the lint trap in the dryer is not adequate if the auxillary blower fan is within 15" of the dryer.

    But thanks for your input ...............:confused:
  13. ballvalve

    ballvalve General Engineering Contractor

    Messages:
    3,261
    Location:
    northfork, california
    Did you mean 15 feet? You are already 36" up. Stilll seems to me the aux fan should keep the lint in suspension for the run without the second screen. Probably the mfg's lawyers needed that added. Curious about how much lint you get on that aux screen? whats the cleaning ratio vs the one on the dryer? 1/1 , 5/1?
  14. Agu

    Agu New Member

    Messages:
    66
    Location:
    Tampa, FL
    Yes I did mean to post 15' , good catch.

    The secondary screen catches about half as much as the primary dryer screen. According to Fantech the secondary screen is to prevent lint buildup on the fan blades. From the lint removed from the second lint trap I believe them. Just wish it was more user friendly and less messy.
  15. ballvalve

    ballvalve General Engineering Contractor

    Messages:
    3,261
    Location:
    northfork, california
    You got 907 views on 13 replies! Looks like dryer vents needs its own forum. And maybe dryers need 2 stage filter screens that come out in one pull.
  16. Agu

    Agu New Member

    Messages:
    66
    Location:
    Tampa, FL
    After some use I've learned a couple of things.

    When cleaning the lint filter turn on the dryer for a few seconds so the auxillary fan is running. That way loose lint gets sucked into the screen instead of falling on clean laundy,the dryer, or on the floor when the lint trap is opened.

    The aux fan is on a 10 minute timer. To shut it off when the dryer cycle is done I've installed a switchable power strip. Although the fan doesn't use much power, sucking out heated or air conditioned air is a waste of energy. Don't know if there's a code for this but if it's a code violation please ignore my comment ;).
  17. Chris in Dallas

    Chris in Dallas New Member

    Messages:
    12
    Location:
    Dallas, TX
    Hello, this is my first post here. Regarding boosting the dryer exhaust: what about boosting the dryer intake? The fan could be a a cheapy (not a $200 exhaust booster, made to work with lint), and the air source could be from outside the house. Obviously, the intake would require some fabrication, and large leaks in the cabinet would have to be sealed. Could providing some pressure to the make-up air improve exhaust venting? Would it affect dryer performance?
  18. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,819
    Location:
    New England
    Unless there is an obstruction, a dryer pushes as much air as it can. The problem is the outlet is too restricted, so new air into the space, while important, is rarely a big issue. Now, for max economy, a heat recovery system for that air pulled into the room might be a good idea, but just ensuring more air won't cut it...a booster fan in the duct does.
  19. Chris in Dallas

    Chris in Dallas New Member

    Messages:
    12
    Location:
    Dallas, TX
    I don't think I was clear enough in my post. If the dryer intake is sealed, so that the make-up air is pressurized in the dryer, how would that affect performance?
  20. Chris in Dallas

    Chris in Dallas New Member

    Messages:
    12
    Location:
    Dallas, TX
    For heat recovery, I'm using a coaxial counterflow setup, with make-up air for the gas dryer coming from outside of the house. 4" duct for centered in 6" supply duct. Will have a 4" dryer booster right after a supplemental lint screen after about 6' of run with two 90 degree bends and one 45 bend. They join via a 6" tee right above the dryer (stacked dryer, vents through ceiling in closet in middle of house, then goes through attic, which is sealed and semi-conditioned), and will separate right at the gable, so that each can have its own spring-loaded damper. The 6" duct supplies air to the dryer, via a plenum that covers almost all of the intake louvers on the dryer. Shortly after the booster, the duct will slope downhill to let any condensate flow out. There shouldn't be any condensation prior to the booster fan.
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