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venting dryer --which way exhaust go??

jim_14
jim_14 Member Posts: 271
in THE MAIN WALL
like steam?

Anyway, Im placing a washer/dryer stack unit on my second floor. We are venting into a wide vent that runs from the first floor to the roof. All this vent does is go from the bathroom to the roof- postive because I have the ceiling open on floor 1 and verified vent ends there.

I am pretty sure since hot air rises that the dryer exhaust will go upwards towards the roof rather then downwards towards the bathroom.

Basically we are tapping into the sheet metal vent as it passes by and using that to get the dryer exhause to go outside...

Anybody try this before? Am I right about the exhaust going up ?? Pic is the end of vent on roof that curves over..

BTW we are going from 4" vent into this one which I believe is 16" wide

Comments

  • EJW
    EJW Member Posts: 321


    Probably not the best idea jim. The condonsation from the dryer will run down the line to the bath if it is a vertical drop. Is the dryer near a outside wall you could go out? EJW
  • jim_14
    jim_14 Member Posts: 271
    no Im in an attached house

    and the dryer is on a wall where my house is "attached" so the only way out is up!

    The other end of the vent curves the opposite way into a small bathroom. Picture a big "S". so no straight verticle drop..

    I understand about the condensation issue, but Im hoping since theres another curve at the bottom that it wouldnt be an issue.

    Do you think that the exhaust will go upwards towards the roof?
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928


    The exhaust will go to wherever the air pressure is lower--maybe the outdoors, maybe the indoors. Realize that penetrations through such a roof are a PITA, but really best (and possibly the only legal way) to keep them separate.
  • EJW
    EJW Member Posts: 321
    Vent

    When combined with another vent it will take the path of least resistance. If the bathroom vents damper does not completely close thats where its going. Large duct work and the length of this run will give you a condonsate problem. EJW
  • thfurnitureguy_2
    thfurnitureguy_2 Member Posts: 74


    just a thought, Lots of junk from a dryer vent you may not want in your bath vent.
  • Uni R
    Uni R Member Posts: 663
    In the box...

    Usually we are forced to think outside the box but in this case it might be good to think inside the box. Could you run your vent into the large vent and then run it through the other vent and terminate it with the other vent? It wouldn't be fun sealing where you go into the vent, but at least you are controlling where it is actually venting.
  • Bob Harper
    Bob Harper Member Posts: 1,097
    lint fire

    Do you want a lint fire in this duct? The change from small to large duct will cause your velocity to drop sharply. The condensation will collect lint like papier mache'. When it ignites, flames will lick into the bathroom as well as through any leaks in the duct. Any joints will collect lint as well.
  • jim_14
    jim_14 Member Posts: 271
    the bath vent

    is for a tiny bathroom on my first floor, just a tiny bowl and a toilet.

    We've always kept that vent closed anyway.. it never did much good anyway.. there is no blower fan to move air out.. I figure it was just there to meet that NYC code that says all bathroom must be ventilated
  • jim_14
    jim_14 Member Posts: 271
    No I dont want a fire thru this duct!!!

    Am i too assume that the lint will drop to the bottom of this duct (rather then make it out onto the roof)??

    Besides, wouldnt the temp exiting the 4" vent drop when going into the larger 16" duct??

    I have no problem opening the bathroom end every 6-12 months and vacuuming out the lint that may be sitting there.

    Besided IMO its alot easier then going up on the roof every week and cleaning out a 4" vent door
  • Constantin
    Constantin Member Posts: 3,796
    I'd consider...

    ... rigid round ductwork meant for dryers as a liner inside the extant vent box at the very least... that'll keep the lint and other junk out of the bathroom below, whether its damper is open or not.

    A stainless, smoothwalled liner will not only ensure that air velocity stays high enough to get the lint out of the house, it won't accumulate lint the way corrugated ducts do.

    "Upstairs", I'd have it terminate a bit beyond the end of the extant vent to ensure that no dryer gases get recirculated into the house.

    Lastly, I would check with the code authorities to ensure that your vent retrofit is legal. There is no point in installing something that could cause you massive headaches later... When in doubt, simply install a new, separate penetration through the roof.
  • freon12
    freon12 Member Posts: 15
    piping

    you should use double wall vent pipe and tape the seems(not screwed).. depending on the vertical lift you might add a duct booster that is thermostatically controled or a relay off the dryer control panel..

    Its more of an issue if its a gas dryer vs electric
  • Weezbo
    Weezbo Member Posts: 6,232
    Jim....

    i have seen this in my experiential realm...and it aint good. is there a way using a soffit chase to outside wall? or drop a floor and out through rimjoyst ? a way to move the dryer to an outside wall? not wanting to alarm you in any way just to give you an idea about what i may mean by Not Good...the stuff caught fire went through the building caught the roof on fire spread acreoss the top of the roof burned a hole in the ajoing building froze all the pipes melted the through the roof vents of abs the water damage was pretty basd too. and luckily for the guy he owned all three buildings that were tied together ....well ...er...we got to slam in a boiler and fix alotta leaks so i guess it werent all bad . i re did all kinds of stuff and figuring which way charlie on the piping was extreme :) the DWV was an equal challange....
  • Rudy
    Rudy Member Posts: 482
    no.

    The lint will not fall back down. The exhaust stream is moist, and the moist lint will cling to everything inside that duct.

    This is a bad idea, and against code due to the irregular and sharp interior of the duct, for starters..

    If you decide to illegally vent this anyway, and clean it every month, what happens down the road when you sell?

    The only way I see is to line it with smooth 4" metal duct, no screws.
  • Steve Paul
    Steve Paul Member Posts: 83
    dryer vents

    The large duct that you want to use to vent the dryer was most likely put together with sheet metal screws. The code specifically prohibits using piping put together with screws. Lint will catch on the screw tips and create a fire hazard. DONDOIT!
  • jim_14
    jim_14 Member Posts: 271
    bob i see your point and may do that, but by measurements

    I have about 3 feet of that duct from the place we cut into until it gets to the roof. I have some access to the other end of thsat duct where it cuts into my kitchen before hitting my bathroom and it doesnt look like any screws were used.

    In fact in my kitchen is a big tape job, tape over an old opening that we have no idea what it was used for.

    I cant see it being used for a stove vent since the stove is on the oppposite side along with the original gas cock. And besides they wouldnt vent a stove into duct that has an opening into a bathroom would they?

    I think Im going to moniter the situation and see how much lint get stuck.. Im figuring the 3 feet of big duct is short enough to let most lint escape.. I'll find out in a few months.. Im on the roof at least twice a year and I think I can take that end cap off and look straight down. If its bad then I'll drop a solid 4" sheet metal dryer pipe down
  • jim_14
    jim_14 Member Posts: 271
    my mistake bob,

    my duct extends about another 3 feet onto the roof ,so Id say its about a 6 foot uphill battle for the lint
  • jim_14
    jim_14 Member Posts: 271
    what do you mean by

    add a duct booster that is thermostatically controled ??

    is this something that has to be wired into an electric source?
  • freon12
    freon12 Member Posts: 15
    controls

    Theres a few ways to control them:

    pressure swith- senses dryer motor pressure

    thermostat in duct- sense's heat from dryer

    relay- when power is applied to dryer it turns on fan

    I have installed a few multiple dryers into a single vent in commercial applications, you have to put your engineering cap on with some of them. Total cfm, back draft dampers,clean outs etc. Some of these systems are quite elaborate.....


    only one I remember off hand is www.aeroflo.com for residential use...

    hope that helps...
  • Kal Row
    Kal Row Member Posts: 1,520
    a gas drier vent is a flue pipe, and can contain CO!!!...

    put in a inline boost fan and get it ouside - stat!!!

    the boost fan will save you money with shorter drying times, also intruct whomever is doing the drying to clean the lint filter every 1/2hr when doing towles - will save even more,
  • DaveGateway
    DaveGateway Member Posts: 568
    get a condensing dryer, for goodness sake

    Rather than running a duct inside your existing duct and waiting for it to clog, or worse yet taking a chance where this exhaust may end up, you might consider getting a condensing dryer. these units are electric and the excess heat is turned into a liquid which goes down the drain. They have them at PC Richard--Bosch and also some other brands. This will save you alot of headahes!
  • Kal Row
    Kal Row Member Posts: 1,520
    yeah! http://www.haieramerica.com/products.php?pid=57

  • Joe_30
    Joe_30 Member Posts: 85


    Anyone have a guestimate for the cfm's vented by average home clothes dryer, so as to arrive at a size of fan to use to pull makeup air into the same room from outside?
  • freon12
    freon12 Member Posts: 15
    cfm

    150 cfm
  • jim_14
    jim_14 Member Posts: 271
    speaking of CO

    where can I get a good CO detector?

    I know there is one that is really good, all the pro's recommend it but I forgot the site

    also is there a good CO/Smoke detector combo unit that is good?
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