Joe_Carrick

Clothes Dryer Vent

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The local building department is requiring a maximum length of vent for a clothes dryer of 15' with at most 2 elbows.  The location of the Laundry within the house makes this virtually impossible.  The Laundry is on the 1st floor of a 2 story home but is at least 20' from any exterior wall.  There is a crawl space with at least 4' headroom.

 

How can this be resolved? 

 

 

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Either that or maybe get an engineer to sign off on one going through the roof if you can prove enough stack effect.  This would be pretty easy for us to do in Alaska I imagine.  Maybe not so much in California.  Downside of course is cleaning the screen on the roof or the lint on the roof.  Yeah, that's not a good idea.  Forget I said it.

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17 hours ago, Alaskan_Son said:

Either that or maybe get an engineer to sign off on one going through the roof if you can prove enough stack effect.  This would be pretty easy for us to do in Alaska I imagine.  Maybe not so much in California.  Downside of course is cleaning the screen on the roof or the lint on the roof.  Yeah, that's not a good idea.  Forget I said it.

 

 

I have seen them in the Roof before , for a 2nd floor laundry, I had to go to discover why the dryer kept drying after the Owner's Appliance Guy wouldn't warranty anymore Dryers and told the Owner to have a Contractor look at the Vent...I discover the Roofer had put the Grille in the Roof Cap in backwards and upside down and had blocked the Flapper from Opening.

 

M.

 

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Never had to use one before.   But useful to know.  Do these have supporting documentation which allows them to be installed in compliance with code.?   Can't remember the exact verbage but often code will give a "or per manufacturer specs".  Thanks in advance for the additional knowlege.

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They can have a longer length but you need a 6" vent.

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1 hour ago, VisualDandD said:

Never had to use one before.   But useful to know.  Do these have supporting documentation which allows them to be installed in compliance with code.?   Can't remember the exact verbage but often code will give a "or per manufacturer specs".  Thanks in advance for the additional knowlege.

I don't remember exactly where I found it but with that fan the vent can be up to 60', maybe more.  In my case the vent is only 25' so it's well within the limit.

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15 hours ago, DRAWZILLA said:

They can have a longer length but you need a 6" vent.

Perry, is that documented in the CRC?

 

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Ok simple fix is repurposes laundry, and stretch line between two poles in back yard..........

Do not forget the wash tub in back yard...........

All so saves energy............ and cloths smell fresh unless fire near by.......

 

:)

I just had to add this option, Joe

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52 minutes ago, OkcDesigner said:

Ok simple fix is repurposes laundry, and stretch line between two poles in back yard..........

Do not forget the wash tub in back yard...........

All so saves energy............ and cloths smell fresh unless fire near by.......

 

:)

I just had to add this option, Joe

Not in California you got to have laundry Code 

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10 hours ago, Gawdzira said:

Perry, is that documented in the CRC?

 

(b) If three 90-degree elbows are used in the vent system,

then the maximum vent capacity listed in the tables

must be reduced by 10 percent (see Section 504.2.3

for single appliance vents). This implies that the 5-

inch-diameter vent has an adjusted capacity of only

110,000 Btu per hour. In this case, the vent system

must be increased to 6 inches in diameter (see

calculations below).

122,000 (0.90) = 110,000 for 5-inch vent

From Table 504.2(2), Select 6-inch vent

186,000 (0.90) = 167,000; This is greater than the

required 120,000. Therefore, use a 6-inch vent and

connector where three elbows are used.

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On ‎1‎/‎11‎/‎2018 at 9:34 PM, Alaskan_Son said:

Either that or maybe get an engineer to sign off on one going through the roof if you can prove enough stack effect.  This would be pretty easy for us to do in Alaska I imagine.  Maybe not so much in California.  Downside of course is cleaning the screen on the roof or the lint on the roof.  Yeah, that's not a good idea.  Forget I said it.

MY HOUSE WAS BUILT IN 2014 AND WE HAVE ONE OF THOSE THROUGH THE ROOF DRYER VENTS. Have to clean them out to be safe.

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25 minutes ago, DRAWZILLA said:

MY HOUSE WAS BUILT IN 2014 AND WE HAVE ONE OF THOSE THROUGH THE ROOF DRYER VENTS. Have to clean them out to be safe.

 

Yeah, I did that on one of my own personal houses years ago and I hated it.  We almost bought a new dryer one time thinking the dryer had gone out on us till we realized the stupid screen was just totally blocked up with lint.  So, we had to climb up on the roof and clean it off every few months.  The alternative is to do away with the screen and use a flapper but then you end up with an ugly “lint stain” on your roof just below the vent hood.  

 

Anyway, I only go through the roof now as a last LAST resort.  

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On 1/12/2018 at 0:44 PM, joey_martin said:

 

I know you were just trying to be helpful but I think these things are absolutely terrible unless MAYBE if you live in the desert.  Introducing all that moisture into a house, and at such an extreme rate is a recipe for disaster.  

 

We actually had one of those things in a trailer we lived in.  I think we lived there about a year and a half.  When we moved out, I kid you not, there was black mold behind almost every piece of furniture that lived up against an exterior wall.  It may have been coincidence, but my wife and I both inexplicably developed some new health problems around that time as well. 

 

Anyway, just to be fair, this was in Alaska where moisture inside the home is a much bigger problem than it is in warmer climates but the same principle holds true in a large part of the country.  

 

I would just really encourage anyone seriously considering one of these devices to proceed with EXTREME CAUTION and even then...only if you live in the dryest and warmest of climates or REALLY REALLY understand what you’re doing.  That’s a lot of moisture to dump into the air at one time.  

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If this helps: 2015 IRC code (Not sure what CA code is)

M1502.4.5.1 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 M1502.4.5.1. The maximum length of the exhaust duct does not include
the transition duct.

TABLE M1502.4.5.1 DRYER EXHAUST DUCT FITTING EQUIVALENT LENGTH
DRYER EXHAUST DUCT FITTING TYPE EQUIVALENT LENGTH
4 inch radius mitered 45 degree elbow 2 feet 6 inches
4 inch radius mitered 90 degree elbow 5 feet
6 inch radius smooth 45 degree elbow 1 foot
6 inch radius smooth 90 degree elbow 1 foot 9 inches
8 inch radius smooth 45 degree elbow 1 foot
8 inch radius smooth 90 degree elbow 1 foot 7 inches
10 inch radius smooth 45 degree elbow 9 inches
10 inch radius smooth 90 degree elbow 1 foot 6 inches
 

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46 minutes ago, Greg_NY61 said:

If this helps: 2015 IRC code (Not sure what CA code is)

M1502.4.5.1 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 M1502.4.5.1. The maximum length of the exhaust duct does not include
the transition duct.

TABLE M1502.4.5.1 DRYER EXHAUST DUCT FITTING EQUIVALENT LENGTH
DRYER EXHAUST DUCT FITTING TYPE EQUIVALENT LENGTH
4 inch radius mitered 45 degree elbow 2 feet 6 inches
4 inch radius mitered 90 degree elbow 5 feet
6 inch radius smooth 45 degree elbow 1 foot
6 inch radius smooth 90 degree elbow 1 foot 9 inches
8 inch radius smooth 45 degree elbow 1 foot
8 inch radius smooth 90 degree elbow 1 foot 7 inches
10 inch radius smooth 45 degree elbow 9 inches
10 inch radius smooth 90 degree elbow 1 foot 6 inches
 

 

The Calif. code really wants you to hire a mech. engineer to figure it out.:lol:

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No kidding?! I don't know how anything is being built down there with all the regulations and specs you have to submit with your drawings.

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14 hours ago, Greg_NY61 said:

No kidding?! I don't know how anything is being built down there with all the regulations and specs you have to submit with your drawings.

Here's how, the builders ignor it in the field:lol:

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If you know the dryer model you can check its' specs.  Some units have a stronger exhaust fans.  The code allows you to use the manufacture's installation requirements, but I would still pass it by the building official to head off problems from the field inspectors. 

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Interesting link. I just circled back to the dryer spec for the project I am just finishing up (building). My intention was to install a duct booster on the line because we exceed the code for California of 14'. See the pic for the dryer model manual regarding rigid ducting. We will have the equivalent of 3 90 deg elbows and about 20' of  4" rigid metal ducting. We were careful not to use screws in the duct work. Still, I am hesitant to do anything short of ensuring the client puts in that booster.

dryer ducting snip.jpg

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Alan,

Check with the local building department.  In San Diego they would not accept the in-line booster.

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Joe, did you do some other mechanical system for yours? What was your eventual solution?

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