# DRYER DUCT LENGTH



## darcar (Feb 24, 2010)

Can somone explain why the IRC section M1502.4.4.1 states the max length fro dryer duct is 25' and the IMC section 504.6.4.1 allows 35' .

Now lets look at GAS dryers... IRC section G2439.5.5.1 has a max of 35' and the IFGC section 614.6.5.1 also allows 35' .

 is M1502 wrong or?... what type of dryer is it regulating and why is the IMC different ?

Thanks in advance


----------



## jim baird (Feb 24, 2010)

Re: DRYER DUCT LENGTH

Which year?

General answer to why IMC may be diff is that its application is non-residential.


----------



## darcar (Feb 24, 2010)

Re: DRYER DUCT LENGTH

sorry... 2009

Why would a residential non-gas dryer be able to have a longer exhaust than a gas dryer?


----------



## D a v e W (Feb 25, 2010)

Re: DRYER DUCT LENGTH

Ignition source? Just speculating, not sure.


----------



## Paul Sweet (Feb 25, 2010)

Re: DRYER DUCT LENGTH

Why would a residential non-gas dryer be able to have a longer exhaust than a gas dryer?

Because different subcommittees wrote the codes.


----------



## D a v e W (Feb 28, 2010)

Re: DRYER DUCT LENGTH

Nice  :roll:


----------



## fatboy (Feb 28, 2010)

Re: DRYER DUCT LENGTH

Yup........I just amended so that both read 35'........from what I've researched....haven't found a dryer that wouldn't make it. (although, I'm sure the is some out there)


----------



## Uncle Bob (Feb 28, 2010)

Re: DRYER DUCT LENGTH

Ya'll wouldn't overlook this would you?

2009 IRC, 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.

(should be the preconcealment inspection)

2006 IRC, M1502.6 Duct length.

Exceptions:

1.  Where the make and model of the clothes dryer to be installed is known and the manufacturer's installation instructions for the 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 manufacturer's installation instructions.

Some allow as much as 80'; and/or for shorter runs, (2009 IRC) 2 1/2" duct;

(see page 5)

http://amana.com/assets/amana/pdfs/INST ... ion_EN.pdf

Ain't America Great?

Uncle Bob


----------



## beach (Mar 2, 2010)

Re: DRYER DUCT LENGTH

So..... what if you move, take your dryer, and someone else moves in with a dryer that's rated for a shorter vent run?


----------



## High Desert (Mar 2, 2010)

Re: DRYER DUCT LENGTH

Install a sprinkler head in the dryer duct.    

Actually, that is a problem and there is no way to regulate it. I hate that code section.


----------



## beach (Mar 2, 2010)

Re: DRYER DUCT LENGTH

Nahhhhhhhhh......the sprinkler head would just collect lint! :lol:


----------



## High Desert (Mar 2, 2010)

Re: DRYER DUCT LENGTH

Well I tried. The heat with the built up lint would probably set the head off anyhow, then you'd have to dry you clothes with your solar dryer.


----------



## beach (Mar 2, 2010)

Re: DRYER DUCT LENGTH

I'm going to market a solar clothes dryer and call it a "Clothes Line". Kind of a catchy name.... :mrgreen:


----------



## conarb (Mar 2, 2010)

Re: DRYER DUCT LENGTH



			
				Uncle Bob said:
			
		

> 2006 IRC, M1502.6 Duct length.Exceptions:
> 
> 1. Where the make and model of the clothes dryer to be installed is known and the manufacturer's installation instructions for the 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 manufacturer's installation instructions.


So he gives you the manufacturer's instructions for one of the dryers that flush lint down the waste line, no dryer vent required. I had one of those in 1958 and they are back.


----------



## Uncle Bob (Mar 3, 2010)

Re: DRYER DUCT LENGTH

Beach,

"So..... what if you move, take your dryer, and someone else moves in with a dryer that's rated for a shorter vent run?"

Oh, it gets better (more ridiculous);

"2009 IRC, M1502.4.5  Length identification.  Where the exhaust duct is concealed within the building construction, the equivalent lengh of the exhaust duct shall be identified on a permanent label or tag.  The label or tag shall be located within 6 feet of the exhaust duct connection."

That means that (for all clothes dryer ducts); other than where the dryer location is adjacent to an  exterior wall; this "permanent label or tag" is required; for all homes built after the 2009 IRC is adopted.

Now, we need to require an inspection (like when a water heater is replaced) for the repacement of clothes dryers; to insure that the new dryer's manufacturer's length limitation is equivalent to or less than, the old one (listed on the tag).  If not, the homeowner must buy a dryer that meets the same duct length capability as the old one.   :roll:

Are we having fun yet?

Uncle Bob


----------



## vegas paul (Mar 3, 2010)

Re: DRYER DUCT LENGTH

UMC limits residential dryer ducts to 14 feet, with maximum of 2 90 degree bends.  Deduct 2 feet (from the 14) for every 90 degree bend in excess of 2.

This is regardless of gas/electric, by the way.


----------



## Uncle Bob (Mar 3, 2010)

Re: DRYER DUCT LENGTH

Paul,

"UMC limits residential dryer ducts to 14 feet, with maximum of 2 90 degree bends. Deduct 2 feet (from the 14) for every 90 degree bend in excess of 2."

(Don't have my UMC book with me.)

I like it, but, believe enforcement would restrict washer/dryer locations to exterior walls in most homes.  With nominal 8' ceiling heights; that only leaves approximately 6' to exterior wall location when duct is up wall to attic and out exterior wall.

You could have 14' to exterior wall; if the wall line behind the dryer extended 14' or less (without interuption) to the exterior wall.

That severely restricts new home designs.  Are they enforcing this where you are?

Uncle Bob


----------



## TJacobs (Mar 3, 2010)

Re: DRYER DUCT LENGTH

In 2006 they all matched, IRC, IFGC and IMC.  Sounds like someone won a "victory" at the code changes and didn't cover all the bases.

We sure wouldn't want to restrict designers in the interest of fire prevention.  Plus, there weren't good statistics from the fire service to back up the 25' rule.  I know, I know, fires don't start in clothes dryers... 

Maybe they thought that since homes will be sprinklered they could push the envelope.  How is that working out so far?


----------



## vegas paul (Mar 3, 2010)

Re: DRYER DUCT LENGTH

UB, yeah, they were enforcing it in Southern Nevada, but allowed longer runs if calculated by a mechanical engineer - remember that most homes in Southern Nevada are fully engineered anyway...

Haven't figured out if it's enforced per the UMC here in Salina, but we're on the UMC also.


----------



## Plans Approver (Mar 3, 2010)

Re: DRYER DUCT LENGTH

We don't need no stinking mechanical codes!


----------



## Coug Dad (Mar 3, 2010)

Re: DRYER DUCT LENGTH

I made my own version of this back when I had electric dryers.  It worked great and added heat and some humidity on especially cold and dry winter days.  Only used it on certain days and  it vented to outside when not it use.  I kept an eye on the humidty levels to make sure I was not getting condesation.  Not much lint made it past the lint collector within the dryer.  I have used gas dryers for the last 20 years, so not much of an opportunity to do it now.


----------



## STB (Mar 4, 2010)

Re: DRYER DUCT LENGTH

http://shop.dryerbox.com/s.nl/it.A/id.253/.f


----------



## beach (Mar 4, 2010)

Re: DRYER DUCT LENGTH

Calif. UMC (based on 2006 UMC) requires max. 14' BUT it also states: "Unless otherwise permitted or required by the dryer manufacturer's instructions and approved by the AHJ, domestic dryer moisture exhaust ducts shall not exceed a total length of 14'......"

Of course, the AHJ isn't going to approve it around here (I hope)........for the reasons stated in my other post


----------



## JBI (Mar 4, 2010)

Re: DRYER DUCT LENGTH

Jake - " I know, I know, fires don't start in clothes dryers... " But they DO start in clothes dryer VENTS! Been there, seen that, more than once...


----------



## conarb (Mar 4, 2010)

Re: DRYER DUCT LENGTH



			
				John said:
			
		

> " But they DO start in clothes dryer VENTS! Been there, seen that, more than once...


The solution to this, and everything else, is to put fire sprinklers in the vents.


----------



## beach (Mar 4, 2010)

Re: DRYER DUCT LENGTH

Didn't you see post 10, 11 and 12????? :?:


----------

