# drier vent developed length



## BSSTG (Mar 12, 2014)

Greetings,

I haven't seen this issue pop up in years. What are folks doing nowadays to rectify this issue? I've got a R2 plan with vents being too long.

BSSTG


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## ICE (Mar 12, 2014)

Are there still requirements in the code or has that been replaced with with "Follow the manufactures installation instructions"?

I'll go look.

Here it is:

504.3.1 Domestic Clothes Dryers. Where a compartment or space for a domestic clothes dryer is provided, not less than a 4 inch diameter moisture exhaust duct of approved material shall be installed in accordance with this section and Section 504.0. Where a closet is designed for the installation of a clothes dryer, an opening of not less than 100 square inches for makeup air shall be provided in the door or by other approved means.

504.3.1.1 Domestic Dryer Vents. Domestic clothes dryer moisture exhaust ducts shall be of metal and shall have smooth interior surfaces.

Exception: Listed clothes dryer transition ducts not more than 6 feet in length shall be permitted to be used in connection with domestic dryer exhausts. Flexible clothes dryer transition ducts shall not be concealed within construction.

504.3.1.2 Length Limitation. *Unless otherwise permitted or required by the dryer manufacturer’s instructions and approved by the Authority Having Jurisdiction*, domestic dryer moisture exhaust ducts shall not exceed a total combined horizontal and vertical length of 14 feet, including two 90 degree elbows. A length of 2 feet shall be deducted for each 90 degree elbow in excess of two.


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## cda (Mar 12, 2014)

How do you know they are to long??

Can they meet the manufacture

Or have engineer design it and show you the calcs


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## cda (Mar 12, 2014)

What year edition are you using

Yes we see it and some have used the tag 504.6.5 2009 edition


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## mtlogcabin (Mar 12, 2014)

The 2012 IMC has more options and reflects the newer dryers and exhaust elbows on the market today.

Even if the 2012 is not adopted you could accept it if the contractor request you do so under "alternate materials and methods"

  504.6.4 Duct length.The maximum allowable exhaust duct length shall be determined by one of the methods specified in Section 504.6.4.1 or 504.6.4.2.

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.

TABLE 504.6.4.1

DRYER EXHAUST DUCT FITTING EQUIVALENT LENGTH

DRYER EXHAUST DUCT FITTING TYPE	EQUIVALENT LENGTH

4² radius mitered 45-degree elbow 	2 feet 6 inches

4² radius mitered 90-degree elbow 	5 feet

6² radius smooth 45-degree elbow 	1 foot

6² radius smooth 90-degree elbow 	1 foot 9 inches

8² radius smooth 45-degree elbow 	1 foot

8² radius smooth 90-degree elbow 	1 foot 7 inches

10² radius smooth 45-degree elbow 	9 inches

10² radius smooth 90-degree elbow 	1 foot 6 inches

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 degree = 0.0175 rad.

504.6.4.2 Manufacturer’s instructions.

The 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. Where the exhaust duct is to be concealed, the installation instructions shall be provided to the code official prior to the concealment inspection. In the absence of fitting equivalent length calculations from the clothes dryer manufacturer, Table 504.6.4.1 shall be used.

504.6.5 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 (1829 mm) of the exhaust duct connection.


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## BSSTG (Mar 12, 2014)

Greetings,

2009 IRC here. section

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.

The plans indicate a linear footage of 18' and doesn't indicate developed length. I'm afraid they will exceed the 25' max taking into account the required turns and so forth. I will be talking with the architect at a meeting in a bit and will question this.

BS


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## Gregg Harris (Mar 12, 2014)

BSSTG said:
			
		

> Greetings,2009 IRC here. section
> 
> 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.
> 
> ...


Are you sure you do not have a miss-print in you document 25 versus 35?


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## Francis Vineyard (Mar 12, 2014)

Gregg Harris said:
			
		

> Are you sure you do not have a miss-print in you document 25 versus 35?


Gregg, the 2009 IRC still had the 25 and went to 35 in the 2012; but both have the IMC language that ICE provided in post #2 with section 504.3.1.2 including the requirement for length identification tag or label that can be purchase online.


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## mjesse (Mar 12, 2014)

Francis Vineyard said:
			
		

> the 2009 IRC still had the 25 and went to 35 in the 2012.


Did not know that, thanks.

mj


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## north star (Mar 12, 2014)

*( = ) + ( = )*



BSSTG,

As an Alternative Method, see if you can use \ install the long sweep [ type ],

dryer duct elbows.........See the link:

http://www.dryer-ell.com/welcome_dryerell.htm

*( = ) + ( = )*


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## Francis Vineyard (Mar 12, 2014)

Typically would see an on demand booster fan on the roof or in the unit with apartments that do not exhaust directly outside within the prescribed length.


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## Gregg Harris (Mar 12, 2014)

Francis Vineyard said:
			
		

> Gregg, the 2009 IRC still had the 25 and went to 35 in the 2012; but both have the IMC language that ICE provided in post #2 with section 504.3.1.2 including the requirement for length identification tag or label that can be purchase online.


I did not realize that it had not been changed. We changed here in VA. for 2009


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## Francis Vineyard (Mar 12, 2014)

Gregg Harris said:
			
		

> I did not realize that it had not been changed. We changed here in VA. for 2009


Yup and we might foresee what's in 2015 when we adopt 2012 with the double vertical lines in the margin :wink:


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## steveray (Mar 12, 2014)

From the 2009

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.

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 (1829 mm) of the exhaust duct connection.

And now you need to tell them they need a permit for a new dryer so you can verify it is compliant.......Or not....As long as you can find install instructions online you might as well throw the code out the window...


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## Glenn (Mar 12, 2014)

The 2009 IRC is a silly mess...

Chapter 15 provides a 25 ft. max

Chapter 24 provides a 35 ft. max (fuel gas dryers)


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## mtlogcabin (Mar 12, 2014)

All new dryers will easily exceed the 25ft length.


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