dryer vent thing. what is this?

**biglebowski** · 03-15-2010, 07:28 PM

what is this? I saw it once before but forgot to ask about it. I assume it helps catch lint but more info would be great. Also, this was on a gas dryer. Is it a bad idea to have on a gas dryer? I could open it right up and allow CO vent into the house. I recommended replacing the whole line due to several areas of duct tape around it anyway. Any info would be appreciated for future.

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**Jerry Peck** · 03-15-2010, 07:31 PM

I don't know what that thing is, but that foil dryer connector IS NOT ALLOWED to be used, not even for dryer transition duct, and definitely not for the dryer duct.

**Ken Rowe** · 03-15-2010, 08:05 PM

It's an exhaust box. This is what I say about them.

"An exhaust box has been provided on the dryer exhaust to vent some of the moisture and heat from the dryer back into the building. Because of the moisture and lint build up problems associated with these devices they should be removed and the dryer vented to the exterior of the building."

These became popular back in the 70's with the first energy crisis. Not a good idea, especially on a gas dryer.

**biglebowski** · 03-15-2010, 08:08 PM

Originally Posted by Ken Rowe

It's an exhaust box. This is what I say about them.

"An exhaust box has been provided on the dryer exhaust to vent some of the moisture and heat from the dryer back into the building. Because of the moisture and lint build up problems associated with these devices they should be removed and the dryer vented to the exterior of the building."

These became popular back in the 70's with the first energy crisis. Not a good idea, especially on a gas dryer.

thats what i was lookin for. thanks

**Brandon Whitmore** · 03-15-2010, 08:53 PM

but that foil dryer connector IS NOT ALLOWED to be used, not even for dryer transition duct

Jerry, how can you be sure? I've seen a couple specifically listed as transition ducts.

Here's a good little write up: http://www.hcpdc.com/pdf/Dryer%20Ven...quirements.pdf

Also, can you say for sure that all dryer manufacturers prohibit the use of the listed foil ones?

**Bruce Ramsey** · 03-16-2010, 09:02 AM

Not all manufacturers but the Consumer Product Safety Commision people do not like them.

http://www.cpsc.gov/cpscpub/pubs/5022.html

Replace plastic or foil, accordion-type ducting material with rigid or corrugated semi-rigid metal duct. Most manufacturers specify the use of a rigid or corrugated semi-rigid metal duct, which provides maximum airflow. The flexible plastic or foil type duct can more easily trap lint and is more susceptible to kinks or crushing, which can greatly reduce the airflow.

**Michael Thomas** · 03-16-2010, 10:06 AM

(Even if that was a listed transition duct it cannot be used in that manner, the duct must be a single continuous run.)

**Jerry Peck** · 03-16-2010, 06:22 PM

Originally Posted by Brandon Whitmore

Jerry, how can you be sure?

Only because I have not yet found a manufacturer's installation instruction which allows them, and in fact all disallow them.

I've seen a couple specifically listed as transition ducts.

Yep, many will say that they are listed for that use. That does not, however, supersede the manufacturer saying not to use them.

Here's a good little write up: http://www.hcpdc.com/pdf/Dryer%20Ven...quirements.pdf

What that write up seems to try to infer is not what the code it references - the only thing that section really says about transition ducts is that they are limited to 8 feet in maximum length (yes, it also says they shall be listed and labeled for the application, but that listing and labeling does not take precedence over manufacturer's installation instructions for the clothes dryer):
- 504.6 Domestic clothes dryer ducts. Exhaust ducts for domestic clothes dryers shall be constructed of metal and shall have a smooth interior finish. The exhaust duct shall be a minimum nominal size of 4 inches (102 mm) in diameter. The entire exhaust system shall be supported and secured in place. The male end of the duct at overlapped duct joints shall extend in the direction of airflow. Clothes dryer transition ducts used to connect the appliance to the exhaust duct system shall be limited to single lengths not to exceed 8 feet (2438 mm)and shall be listed and labeled for the application. Transition ducts shall not be concealed within construction.
- - 504.6.1 Maximum length. The maximum length of a clothes dryer exhaust duct shall not exceed 25 feet (7620 mm) from the dryer location to the outlet terminal. The maximum length of the duct shall be reduced 21/2 feet (762 mm) for each 45 degree (0.79 rad) bend and 5 feet (1524 mm) for each 90 degree (1.6 rad) bend. The maximum length of the exhaust duct does not include the transition duct.
- - - Exception: Where the make and model of the clothes dryer to be installed is known and the manufacturer’s installation instructions for such dryer are provided to the code 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.
- - 504.6.2 Rough-in required.Where a compartment or space for a domestic clothes dryer is provided, an exhaust duct system shall be installed in accordance with Sections 504.6 and 504.6.1.

Also, can you say for sure that all dryer manufacturers prohibit the use of the listed foil ones?

Yep. Until some manufacturer proves me wrong.

williamsmith · 04-12-2010, 01:20 AM

I really like your post...Its worth and sounds good

**Bob Knauff** · 04-12-2010, 12:30 PM

Ken is correct. The devices were marketed to "save" energy by reclaiming the heat from the drying process. Unfortunately, along with the heat comes the by-products of combustion including CO and as such are very dangerous if not used correctly with a gas fired unit. Also, gas fired or electric, they can dump GALLONS of moisture into the air and we all know what that issue leads to.

In regard to ribbed piping, contact your local fire department and ask about their experience with dryer fires and their causes. I believe you'll be quite surprised at what they have to say. Then you can use that powerful information to bolster your findings and reporting.

You might also contact a local, certified chimney sweep and ask their experience with dryer fires and causes. In my area the sweeps started offering dryer vent cleaning services a long time ago in response to the problem.

If you need yet more back-up text for reporting, check out the CPSC article Overheated Clothes Dryers Can Cause Fires: Safety Alert.

All that being said, the Do-It-To-Yourself stores still sell the unit in question...Hmmmmm

I admit that I had one in MN since they were first introduced back in the day but the ONLY reason I really liked it was the fact that when the dryer is not in use, without the device trap door closed to seal the pipe, LOTS of cold air falls back down the vent pipe into the dyer. In dead of winter the metal of the dryer could actually be cool to the touch and the air space around it noticeably chilly. NOT good for energy conservation not to mention occupant comfort. So we kept it closed when not using the dryer and opened it to direct exhaust outdoors otherwise and it worked great in those modes!

If I saw one in a clients home today I would HIGHLY recommend removing it based on the CO and humidity issues and, without telling them, as a liability issue for the HI!

The ribbed piping issue can be explained to clients as a fire hazard but also the kinks (which commonly happens with ribbed material) and/or lint build up and restrictions greatly reduce air flow in the pipe which equates to much longer drying times which equals more time for them "on the job" AND more money out of their pockets for the power bill! They seem to respond more to the longer work time and more out of pocket expense problems than to the fire issue, in my experience.

**Eric Barker** · 04-14-2010, 06:50 PM

You guys ever consider the chemicals in laundry soaps and softeners. Don't try to look them up on the containers - they're mostly unlisted. What you can be sure of is that the clothes dryer does an efficient job of vaporizing the those chemicals and the vent diverter sends them into the home air. I once asked our local Ace Hardware store about them. They said that they knew the diverters were a safety concern but people asked for them so they sell them. They also sell accordion style drain connectors that on the back side of the package shows "S" traps. With merchants like that my job is secure.