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i need to create venting for a gas dryer. can’t go directly out the back (living space there). will need to run venting up 6′ and over 6′ enclosed in a soffit. my question is what size ducting/other features would optimize venting? 3″ or 4″? from reading posts related to this one i’m skeptical that the lint will actually be exhausted at all, but will accumulate in the vent and actually creating a fire hazard over time. opinions or technical input okay, as long as opinions are substantiated.
thanks ahead of time, guys
brian
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First, look in the owner's manual. Typically they tell you how long a run of 4" duct you can do with various number of elbows. (Such as 30' with no elbows, 20' with one elbow, etc). And how far, if at all, you can run 3" duct work (may be under 10' with one or even no elbows). So look there first. No longer have an owners manual? I've had manufacturers fax my the relevent pages at no cost. Give it try.
If you can't that info for your unit, then here's some generic info: 12' of straight pipe with two 90 degree elbows will be okay for most all dryers *IF* you use rigid metal duct work. Not the all-metal flex stuff. Nor the insulated foil-lined flex stuff. And not 3". And use the good aluminum tape that is really sticky and is designed and sold for sealing ductwock. Not the gray plastic-clothy "duct-tape".
Consider how you are going to get in there in the future to scrub out any collected lint. One of the advantages of installing a duct run within the manufacturer's limits is that it will collect less lint. The air velocity will be higher and there will be less condensation than in an (inappropriately) longer run.
Check the bug screen on the outside every month and clean it off. If not, you'll notice that the dryer does not work as well. And you'll be collecting more lint in the ductwork. -David
*excellent david. you addressed my concerns. the estimate i submitted was for opening the existing wall, furring out 1 1/2" to accomodate 4" vent, (using 2x), and enclosing with drywall, creating soffit to house the horizontal ductwork - but the basis was more intuitive than factual. it was not only the size (diameter) and length of the run that created enough concern for me to post this issue, but also the fact that the venting is being run upward for half its length.much appreciated. will try reaching GE.brian
*Vertical ducts (up or down) shouldn't be a problem if you are within the total length limits and therefore have decent air velocity.
*I agree with everything that Dave said, except I would use a wall or roof jack with no screen to clog, and if at all possible, put a cleanout in the ductwork (like you would a sanitary drain) just in case.
*are you suggesting an ABS cleanout connected with no-hub connectors to the duct? at least it's something, but i believe will be rejected as improper material :( will probably keep the end open as you suggest and will be looking for the best way to clean from that point.brian
*for anyone interested in this topic, here is what i found for what building code has to say:http://www.codecheck.com/mechcode.htm#anchor572911brian
*Brian: I'm sure Tim is suggesting construction from metal ductwork. Either a Tee located at a 90 or a Wye located on a straight run. Such that the exhaust continues on its way. With a cap can be removed and the line snaked to remove deposited lint.
*Brian, I am not suggesting a departure from sheet metal, just meant like the concept of the sanitary cleanout. A sheetmetal Y with the run vertical in place of an elbow with a cap secured by sheetmetal screws on the bottom would do the trick. Would depend on the routing ifit would be accessible enough to be of use, though.
*thanks guys.brian