I have to vent our electric bosch dryer through about 25′ and was talking with the plumber and he said they have been using a lot of thin walled pvc to vent these as they are easier to clean and they are smoother so the lint sticks less, any other ideas?
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Replies
Check the dryer installation instructions- some of them run too hot for PVC.
Bob
That's absolute madness.
Yes, PVC may have less of a tendency to trap lint, but if a fire occurs, the PVC will simply add to the flames. Don't do it! It's not legal for a reason!
Use smooth-wall stainless vent pipe w/o screws and you should be all set. If you want to be a real sweetheart to the maintenance crew, install a cleanout as well.
Stainless steel for a dryer vent?!? That's a very impractical suggestion. PVC duct/vent pipe is also a poor choice for anything above ground.
4" 30 guage galvanized duct/pipe with taped joints is standard and very appropriate. If someone were really anal about the moisture, aluminum duct is readily available and not too expensive.
I agree that galvanized pipe that is taped, etc. is standard practice and should work well. The poster was looking for something very smooth that would not retain lint. Hence the suggestion to go with stainless, which is usually smoother than galvanized. Aluminum is another great option, and less expensive than stainless.My main point was to avoid the use of plastics like PVC, CPVC, and the like. Some people seem to think that just because plastics are being used on heating appliances that using them on dryers should be OK as well. Due to the lint-fire issue, nothing further could be from the truth.For that matter, has anyone come up with a means of having a "cleanout" in these duct systems for dryers that are hard to remove? (think gas)
But in a lint fire aluminum isn't much better than plastic.
Well, that's why I prefer stainless. Besides, in most homes, the vent pipes aren't that long as to make a huge price difference in material costs.Are lint fires hot enough to cause Aluminum to ignite? I thought the ignition temperature was somewhere around 900 degrees C, something that a small lint fire shouldn't really be able to do.
I've never seen aluminum burn, but I've seen it melt on a number of occasions. Don't know the temp, but it doesn't take much to melt it. I would guess that a lint-filled vent pipe with the dryer blower running could easily get things hot enough to melt the Al.Of course, the best "fix" here is to never have a lint fire.
I've never seen aluminum burn, but I've seen it melt on a number of occasions. Don't know the temp"
Dan,
It's somewhere around 1,600F.
IMO it's best to use double wall flue vent.
WSJ
I think Al "sags" and becomes plastic at a significantly lower temperature than that.
Dan,
You are correct. I was thinking of the temp it's often poured at. My mistake. Unlike steel, when it does melt, it happens really fast, and the "plastic" stage is very narrow.
WSJ
Yeah, if you've ever seen an Al can thrown into a campfire, you'll understand that it can go soft at a fairly low temp.
I love it when there is a complete lack of consensus. For a 25 foot run, I think the first thing you should be thinking about is a booster fan. Fan Tech has a couple great models. They also have an outboard lint trap that really works. In speaking with the Fan Tech people, they will tell you that they like the booster fan at least 8 feet away from the dryer, which is not very easy to accomodate, and for this reason, we like to install booster fans at the outside of the home at the end of the run of exhaust pipe. They have this particular model.Once the lint is out, the temperature is less than about 100 degrees and the liklihood of fire is nil. Pick whatever material you like to work with. Each has some advantages.PVC is very smoothwalled and easy to install, but hard to do curves and bends in other than fairly standard sizes like 90's and 45's. I don't think the risk of fire is much of an issue if you have a good booster fan and lint trap which you should have anyway. If you don't have those, any exhaust pipe you use will catch fire. I don't think any such fire will be easily contained within the pipe, whatever the material. So the point is, worry about lint, not the particular material of the pipe.Galvinized comes in a variety of lengths and has fixed and adjustable couplings to make bends. Connecting the lengths is not as easy as PVC, and requires a crimping tool and we use special high temperature adhesive made for furnace exhausts. The pipe is also sealed at those locations with special aluminum foam tape. Buy the good stuff, not just duct tape.Aluminum flex is very desirable because of easy of installation and the ability to bend readily. This is probably the most common material, and is found in about 80-90% of most homes. It has a good track record and again, is easy to install. The ridges cause static pressure more readily than other substances, but with a booster fan that shouldn't be an issue.I think the particular product will depend on your home, the curves, and the exhaust fan you choose, although I think I would favor the 4" galvinized furnace exhaust pipe because it is readily available and certainly overrated temperature wise for the use of a dryer exhaust. It is a PITA to install. My next choice would probably be aluminum because I am lazy. PVC is too rigid and too dificult to bend, but I've used it as well. Fan Tech also sells a clean out and a clean out brush. If you are still confused, I would call Fan Tech and speak with their tech people who will literally design a system for you. Very good product, very nice people.Regards,
Boris"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1934
Yeah, whatever you do, make provisions for cleanout.
The plastic pipe may or may not be OK. Probably is OK for an electric unit. Check dryer specs and local code.
Don't use any sort of corrugated junk, except perhaps for a very short connecting piece to the dryer itself.
PVC isn't allowed. don't.
it doesn't have to be stainless though.
4" galvanized is fine. no screws at the connections
carpenter in transition
what about a ground ???"
"what about a ground ???"What about it?I don't see any need to ground it.But if it is installed correctly it will be grounded by the dryer.
yeah if it is a metal duct, but wouldn't a bond around the pipe be better? especially a flexpipe?"
My background is an EE, but all of my work as been with electronics and software for industrial control systems.My electrical work has been with DIY.But my understanding what get bonded is "metal that is likely to become electrified". Now water pipes end up being connected to many electrical appliances. And cables are ofter run over, near, around, piping. This there are several ways for them to become electrified.For a dryer vent non of that holds other than the connection to the dryer which has it's on ground.
eliminating static buildup is the reason for the jumper, even though the exhaust (air) is usually humid"
Edited 7/12/2005 5:59 pm ET by maddog
grounding the dryer exhaust duct isn't going to prevent static build up - it will just give it a place to jump to.There is nowhere near enough airflow coming out of a dryer to create a spark big enough to ignite any kind of lint.
the ground wire is wrapped spirally around the pipe,more of ####shield than a ground. and fastened at one end onlysome people use the plastic flex pipe and attach it to the dryer and the vent with the ty-raps that come with the pipe. the thinking is to reduce the clogging inside the flex"