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Dryer Vents

                                      What the code says:

See the adopted code for the complete text ( for copies contact the International
Code  Council at thier web site).

 CLOTHES DRYERS EXHAUST

1.  Dryer exhaust systems shall be independent of all other systems, shall convey the moisture to the outdoors and shall terminate on the outside of the building. Exhaust duct terminations shall be in accordance with the dryer
manufacturers installation instructions. Screens shall not be installed at the duct termination. Exhaust ducts shall not be con-
nected with sheet-metal screws or fastening means which extend into the duct. Exhaust ducts shall be equipped with a back-
draft damper. Exhaust ducts shall be constructed of minimum 0.016-inch-thick (0.406 mm) rigidmetal ducts, having smooth
interior surfaces with joints running in the direction of air flow. Flexible transition ducts used to connect the dryer to the exhaust duct system shall be limited to single lengths, not to exceed 8 feet (2438 mm) in length and shall be listed and labeled in accordance with UL 2158A. Transition ducts shall not be concealed within construction.
Exception: This section shall not apply to listed and labeled condensing (ductless) clothes dryers.

2.  Exhaust duct size. The diameter of the exhaust duct shall be as required by the clothes dryer’s listing and the
manufacturers installation instructions.

3. Length limitation. The maximum length of a clothes dryer exhaust duct shall not exceed 25 feet (7620 mm) from the
dryer location to the wall or roof termination. The maximum length of the duct shall be reduced 2.5 feet (762 mm) for each
45-degree (0.79 rad) bend and 5 feet (1524mm)for each 90-degree (1.6 rad) bend. The maximum length of the exhaust duct does not include the transition duct.
Exceptions:
1. Where a clothes dryer booster fan is installed and listed and labeled for the application, the maximum length of the exhaust duct, including any transition
duct, shall be permitted to be in accordance with the booster fan manufacturer’s installation instructions.
Where a clothes dryer booster fan is installed and not readily accessible from the room in which the dryer is located, a permanent identifying label shall be placed
adjacent to where the exhaust duct enters the wall. The label shall bear the words This dryer exhaust system is equipped with a remotely located booster fan.
2. Where the make and model of the clothes dryer to be installed is known and the manufacturers installation instructions for such dryer are provided to the building official, the maximum length of the exhaust duct, including any transition duct, shall be permitted to be in accordance with the dryer manufacturers installation instructions.




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            All Leading Manufacturer's require the dryer vent to terminate at least 12-inches from ground or any other object. A list of these manufacturer's is below:

MAYTAG:  See Manufacturer's Installation Instructions at : http://www.maytag.com/assets/product/W10099070.PDF page 14 & 15. " Exhaust hoods must be at least 12" from the ground or any object that may be in the path of the exhaust...." 

FRIGIDARE: http://lib.store.yahoo.net/lib/usappliance/GLEQ2152install.pdf

EXHAUST SYSTEM REQUIREMENTS

Use only 4 inch (10.2 cm) diameter (minimum) rigid or flexible metal duct and approved vent hood which has a swing-out damper(s) that open when the dryer is in operation. When the dryer stops, the dampers automatically close to prevent drafts and the entrance of insects and rodents. To avoid restricting the outlet, maintain a minimum of 12 inches (30.5 cm) clearance between the vent hood and the ground or any other obstruction.

WHIRLPOOL / KENMORE: See: Whirlpool Installation Manual : http://www.whirlpool.com/assets/pdfs/product/ZVENTI/W10100920.pdf

GENERAL ELECTRIC: http://lib.store.yahoo.net/lib/usappliance/GLEQ2152install.pdf

ASKO:
http://www.us-appliance.com/askolaundry.html

SAMSUNG: http://www.us-appliance.com


MIEL:
http://www.us-appliance.com/mielelaundry.html


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Clothes Dryer Fire Prevention

Very few people realize the importance
of clothes dryer fire prevention. However,
according to the U.S. Consumer Product
 Safety Commission, there are an estimated
annual 15,500 fires, 10 deaths and 10
injuries due to clothes dryer fires. Several
hundred people a year are also subjected
to carbon monoxide poisoning from improper dryer vent setups. The financial costs come
 to nearly $100,000,000 per year. In some
cases faulty appliances are to blame, but many fires can be prevented
with proper dryer venting.  
 
How a Clothes Dryer Fire Occurs
Lint accumulation and reduced airflow feed on each other to provide
conditions ripe for a fire. Lint is a highly combustible material, which,
interestingly enough, is one of the ingredients in a recipe for home-made
fire starters. A number of dryer vent problems contribute to this.   
                            
A growing problem
Traditionally, most clothes dryers were in the basement. However,
nowadays many newer homes tend to have dryers located away from
an outside wall in bedrooms, bathrooms, kitchens and hall closets.
These new locations mean dryers tend to be vented longer distances
and vents are generally installed with sharp turns and bends to
 accommodate the structure of the home. As a result, dryer vents
are harder to reach, and also create more places for lint to gather.
The ideal solution is to have short, straight, dryer duct venting. However,
a dryer vent booster, while not the ideal approach, can improve your
dryer venting in cases where your venting is longer and/or has more
bends than it should. In addition to creating a fire hazard, if the venting
is too long and/or has two many bends, it will cause your dryer to take
much longer than necessary to dry loads. 

Inside the Dryer
Lint is the biggest culprit here. As you know from cleaning out your lint
filter, dryers produce very large quantities of lint. Most people assume
 their lint traps catch all the lint, and that all they need to do is clean
 them out after each load. However, a significant amount of this lint is
 not caught by the lint trap and builds up inside the dryer-even on the
 heating element! If you are skeptical, try this experiment: pull out the
 lint trap and look underneath it- you may find large mounds of lint staring
at you. Lint can build up on the heating element and in other places inside
 the dryer, causing it to overheat and possibly catch fire. As a rule, a fire
starts from a spark in the machine. However, improper clothes dryer
venting practices outside the dryer can play a key role in this process.

Outside the Dryer
There are many improper dryer vent practices which restrict airflow
and lead to lint buildup, the two main preventable causes of clothes
dryer fires. 
Some of the most common and important dryer vent mistakes are:
1. Dryer vents are too long and/or
have too many bends, but don't use
a dryer duct booster, resulting in lint
buildup. When it comes to dryer vents,
shorter and straighter is better.
 2. Use of flammable, flimsy plastic or
foil duct extenders. Only metal vents
should be used, which is what most manufacturers specify. Metal vents
also resist crushing better than plastic
 and foil, which allows the air and lint
to be carried out of the system. Reduced airflow from build-up or crushing
 can cause overheating and wear out the clothes and appliance faster.
In fact, many state and local municipalities have placed requirements on
new and remodeling projects to include all metal dryer venting. 
3. Inadequate clearance space between dryer and wall. Many people
 create problems by putting their dryer right against the wall, crushing
the venting material in the process. The cumulative effect of reduced
airflow and the resulting lint build-up prevent the dryer from drying at
the normal rate. This causes the high temperature limit safety switch
to cycle on and off to control the heater. Most high temperature limit
safety switches were not designed to continuously cycle on and off, so
they fail over a period of time. 
4. Failure to clean the dryer duct.


Your Dryer May be Failing If:
The clothes are taking an inordinately long period of time to dry, come
 out hotter than usual or if the vent hood flapper doesn't open.
Maintenance is needed in these cases.

Only You Can Prevent Clothes Dryer Fires
Proper Installation & Choice of Building Materials
1. Make sure the dryer duct is made of solid metallic material. Both vinyl
and foil are combustible and spiral-wound surfaces tend to catch lint
more readily. 
2. The dryer duct should vent to the exterior and in no case should it
 vent to the attic or crawlspace. Avoid the use of inside heat recovery
 diverter valves or termination boxes, which do not comply with current
 standards. 
3. Avoid kinking or crushing the dryer duct to make up for installation
in tight quarters -this further restricts airflow. If you really want to save
 the extra space, the Dryerbox is a new invention that allows the dryer
to be safely installed against the wall.
4. Minimize the length of the exhaust duct (maximum recommended lengths
depend on a number of factors, such as number of bends, and vary by
model-check with your manufacturer for their specifications). If this is
 not possible, you can install a dryer duct booster.
5. If at all possible, use 4-inch diameter vent pipe and exterior exhaust
 hoods that have openings of sixteen square inches or more, which offer
the least resistance to air flow.
6. Don't use screws to put your vent pipe together - the screw shafts
inside the piping collect lint and cause additional friction.

Keep the Dryer Duct in Good Condition
Disconnect, clean and inspect the dryer duct run on a regular basis, or
hire a professional company to clean the dryer duct. This will reduce the
fire hazard, increase the dryer's efficiency and increase its lifespan. In
addition, you are less likely to experience water damage. 

Keep Your Dryer as Lint-Free as Possible
By keeping your dryer clean, not only will you significantly reduce the
fire hazard, you will also save money as your dryer will run more efficiently
and last longer. 
To keep your dryer clean:
1. Use a lint brush or vacuum attachment to remove accumulated lint
from under the lint trap and other accessible places on a periodic basis.
2. Every 1-3 years, depending upon usage, have the dryer taken apart
and thoroughly cleaned out by a qualified service technician. 
3. Clean the lint trap after each load.

Alternative Solutions
1. Use a condensing dryer. Unlike conventional clothes dryers, condensing
dryers do require external clothes dryer venting. This significantly reduces
 the risk of a dryer fire. 
2. Use a spin dryer, which uses an extremely fast spin speed to extract
water from the clothes. They extract significantly more water from the
clothes than a washing machine spin cycle does. Spin dryers can be used
 alone or in conjunction with a conventional clothes dryer.

Before You Go....
1. Never let your clothes dryer run while you are out of the house or
even worse, when you are asleep. 
2. Thoroughly read manufacturers' instructions regarding the safe use
of their dryers.
3. If all else fails, you can always use an old-fashioned clothesline. 

         There have never been any reported clothesline fires


A Final Note:

Carbon Monoxide Detectors and Smoke Alarms save
lives. We as building inspectors, contractors and
 consumers have known this for years. But we must
 remain diligent in or training and education efforts. 



 

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