Dryer venting
chrisjohnston2112
| Posted in Mechanicals on
I am building a new home. The laundry room is in the middle of the house, second floor. To vent the dryer I will have to run a pipe approximately 20 feet. I plan to use PVC non-pressure rated pipe.
My questions: 1) how do I know the length limit of the piping before head loss will not allow the dryer to vent, and 2) if I have to reduce the PVC piping from 4-inches to 3-inches where it goes through a 2 x 4, will that be a problem?
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Replies
The dryer will come with instructions indicating how many feet of pipe you can run, and how to account for elbows. You should not reduce the diameter of the pipe mid-run. Can you furr the 2x4 wall with 1x2 and keep the pipe at 4"? I always install a dryer box in the wall behind the machine so that the flex pipe length is as close to zero as possible, check dryerbox.com
Chris,
The use of PVC pipe for venting dryers is a code violation. The International Residential Code requires metal duct. Here is what the IRC says in section M1502.5: "Duct construction. [Dryer] Exhaust ducts shall be constructed of minimum 0.016-inch-thick (0.4 mm) rigid metal ducts, having smooth interior surfaces with joints running in the direction of air flow. Exhaust ducts shall not be connected with sheet-metal screws or fastening means which extend into the duct."
For more information:
http://www.ehow.com/about_5422684_types-pipe-used-dryer-vents.html
Chris, why not a condensing dryer like the Bosch Axxis? It doesn't require venting at all.
It's not the cheapest dryer out there, but it could well be less expensive than the total cost of a long and complex run of ductwork that could lead to problems at a later date?
Thanks to all three of you for the advice! I know PVC is out, thank you Martin! I will investigate the rest
I have the Bosch Axxis and love it. Especially when it's -40C outside and I'm not blowing out all my nice warm air. It's really too bad these things are so hard to come by in North America.. They're great.
Many dryers have a maximum length limit of 25 feet for vent pipe. Each 90 degree elbow is equivalent to 5'. I have not looked in to it but I was told some new dryers can have longer runs, again I do not know if that is true..
I see a lot of poorly installed and designed dryer runs. They end up causing a lot of clogs. Use as few elbows as possible. If you are running the pipe trough an unconditioned space be sure it is insulated. A long run through an attic will cause condensation in the pipe which speeds up the accumulation of lint.
Unfortunately there is no standard on where the vent exits the dryer. They can be left, center or right. and now we have dryers that sit on pedestals. In your design allow enough room behind the dryer to allow for a good connection. I see pipes that are nearly impossible to make a connection to. I see people that take an 8' section of vinyl duct snaked and kinked behind the dryer because it can be so had to connect.
Dryers are on of the leading causes of house fires. Clogged and improperly vented and clogged vents are a large part of this. Clogged vents cause dryers to run excessively resulting in wear to the equipment and clothes and higher utility costs. It is worth it to do it right.