Qod 9-9-2010

[Greg Bell]

A dryer vent should extend no more than ___ feet.

[Jeffrey R. Jonas]

Originally Posted by gbell

A dryer vent should extend no more than ___ feet.

Generally speaking, but there are always exceptions, for longer and shorter runs.

[Barry Adair]

irc and imc have a 10' difference
bottom of this page

[Chuck Evans]

25 based on IRC. Reduce 5ft for each 90 and 2 1/2ft for each 45 bend.

[Brian E. Kelly]

Originally Posted by badair

irc and imc have a 10' difference
bottom of this page

too bad 35' is not a choice smarty pants......

Hey Barry.

[Roy D. Cooke, Sr]

Follow the manfacture specifications ..

[Marcel R. Cyr]

Originally Posted by bkelly2

too bad 35' is not a choice smarty pants......

Hey Barry.

Sometimes it is.
M1501.3 IRC
Where the make and model of the clothes dryer to be installed is known and the manufacturer's installation are provided, the maximum length of the exhaust duct, shall be in accordance with the dryer manufacrturer instructions.
More and more newer dryers are capable of more than the 25'.

And here is a dryer box Barry is talking about.

[Brian E. Kelly]

504.6.4.1 Specified length. The maximum length of the
exhaust duct shall be 35 feet (10 668 mm) from the connection
to the transition duct from the dryer to the outlet
terminal. Where fittings are used, the maximum length
of the exhaust duct shall be reduced in accordance with
Table 504.6.4.1 http://www.dryerbox.com/convertions/...haust_Duct.pdf
TABLE

I believe Barry was referring to this at the bottom of the page.

[Marcel R. Cyr]

I know, I read it.
I was showing what a dryer box was and why at occasions, the dryer vent can exceed 25 ft.
Manufactures instructions dictate that.

Now for a scenario, Maine has mostly cellars, or basements, and that is where you have the dryers most of the time.
Now using the 25 foot rule, that means if the dryer is not installed against the exterior foundation wall at all times with its back to, it will not meet that requirement.
25' is the rule of thumb or code per IRC, so now deduct two 90's, that is 10', and deduct another 90, cause the flex is crumbled and pinched in the back of the dryer hook-up, and that is another 5'.

So you are left with a 10' straight section of duct that you can use.

I will tell you right now that over 75% of dryers in this area do not meet that criteria.
The dryer box saves on the lineal footage and eliminates pinching.

Manufacturer's instructions will prevail on the installation and I am careful on calling out this as a defect, since we can not site Code or should not.

[Christopher Currins]

Originally Posted by rcooke

Follow the manfacture specifications ..

I agree.

http://www.appliance411.com/faq/dryer-vent-length.shtml

[Marcel R. Cyr]

Check this out here, might think different about the IRC requirement part that we are limited to 25'.

http://www.appliance411.com/faq/drye...th.shtml#chart

[Brian E. Kelly]

IRC Code says says 25' or Manufactures Instructions, so calling out Manufacutrers Instructions is Citing Code in a round about way.



M1502.4.4 Duct length. The maximum allowable exhaust
duct length shall be determined by one of the methods
specified in Section M1502.4.4.1 or M1502.4.4.2.

M1502.4.4.1 Specified length. The maximum length
of the exhaust duct shall be 25 feet (7620 mm)from the
connection to the transition duct from the dryer to the
outlet terminal. Where fittings are used, the maximum
length of the exhaust duct shall be reduced in accordance
with Table M1502.4.4.1.

M1502.4.4.2 Manufacturer’s instructions. The size
and maximum length of the exhaust duct shall be determined
by the dryer manufacturer’s installation instructions.
The code official shall be provided with a
copy of the installation instructions for the make and
model of the dryer at the concealment inspection. In the
absence of fitting equivalent length calculations from
the clothes dryer manufacturer, Table M1502.4.4.1
shall be used.

[Marcel R. Cyr]

Never new that installing something per Manufacturers installation manual was a round about Code.
That is a new one on me Brian.

[Brian E. Kelly]

Originally Posted by mcyr

Never new that installing something per Manufacturers installation manual was a round about Code.
That is a new one on me Brian.

Good discussion, gets me thinking...I do not have an 09 IRC copy yet myself and will have to get one.

I do not recall seeing this requirement before either....

M1502.4.5 Length identification. Where the exhaust
duct is concealed within the building construction, the
equivalent length of the exhaust duct shall be identified
on a permanent label or tag. The label or tag shall be
located within 6 feet (1829mm) of the exhaust duct connection.

[Greg Bell]

It is great to see so much discussion over what I thought was such a simple question.

Thanks to all of you that participated.