Dryer Venting
Facts To Consider
Underwriters Laboratories standards 560 and 2158 for clothers dryers require that all dryers listed must specify all metal dryer venting unless otherwise tested. A UL 181 label does not apply to dryer venting. Underwriters Laboratories Inc., an independent testing agency that helps set national safety standards, requires that dryer manufacturers And as if that
weren't reason enough...
Recommendations
Clothes dryer exhausting recommendations
Just as a point of interest, a customer recently wrote me back the following letter:
"include explicit instructions specifying that only rigid or flexible metal duct should be used for exhausting, unless the appliance has been investigated for use with nonmetallic duct."
Maytag and other major dryer manufacturers recommend against the use of plastic flexible duct.
Although plastic flexible duct (cheap and easy to install) might seem like just the thing for exhausting a dryer, it isn't. This type of exhaust duct, which resembles a plastic-covered slinky toy, is not recommended for several reasons.
The Consumer Products
Safety Commission estimates there are 24,000 clothes
dryer fires each year in the United States, amounting to
$96,000,000 in estimated property damage. Lack of
maintenance is the leading cause of dryer fires, and LINT is the leading material to ignite. These fires
can be caused by failure of mechanical and/or electrical
parts within the dryer itself, improper materials being
put into the dryer, and insufficient airflow as a result
of improper installation.
Looks like the guy has algae growing under that p-trap, too!
Never use an exhaust hood with a magnetic damper. The hood should have at least 12 inches of clearance between the bottom of the hood and the ground or other obstruction. The hood opening should point down.
"
As you suspected, clogged venting turned out to be the problem after all-- not in the 8 feet of aluminum exhaust piping from the dryer to the ceiling, nor at the elbow, nor in the first 5 feet of the conduit in the plenum that my shop vac hose could reach, but rather in the balance of the 28 feet total carry to the external wall vent.
The duct cleaning guys ran rotobrush brush agitator powered by en
electric drill as far as they could reach (23 feet). The drill rig clogged and shut down twice. Both times they retrieved the apparatus, they pulled out large 3-4 liter clumps of lint. Then, one of the men took the giant hose attached to their huge HEPA filtered collection device and pressed the end on the ceiling, surrounding the exposed portion of the elbow. After about 10 seconds of suction almost nothing appeared in the clear tube. The guy said, "I guess we got it all," when suddenly a series of really huge lint clumps -- equivalent in volume to about two sweatpant/sweat shirts sets, we found out later -- came whooshing down the pipe. Several of these large clumps were quite heavy from dampness.
The operator held the end of his flexible tubing flush to
the ceiling for about two more minutes, retrieving several more "minor" clumps of lint the size of two-liter soda bottles, before the suction ceased producing any more material.
Now the AutoDry sensor performs to spec, and a set of towels dries in 45 minutes, while normal laundry loads take considerably less time. I suppose we have also eliminated a potential fire hazard from our home.
I'll probably have the duct cleaning guys back in a few years, providing their apparatus extends the entire 28 feet. Some stuff may remain at the end where their rotobrush couldn't reach, although I now see steam pouring forth from the external wall vent when the dryer is in operation.
Without your advice, I doubt I would have concluded that the clog might be in the ceiling conduit, but thanks to you I had eliminated all other plausible avenues.
Thanks again and best regards",
Sam Bays
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