dryer vent duct is too long

[gregtwojeeps]

At work we have a gym where a LOT of towels are used that the owner maintains. The architect/builder put the washer /dryer in the one car garage out of the way and there is NO physical space to move the W/D elsewhere, or I would have done so already. ...

The mechanical contractor that installed the 4 in. round metal vent for the dryer had to run it up the wall about 9 ft. and then across the steel ceiling bar joists. He exited the vent duct out through the 8 in. cinder block and brick, right above the 10 ft. tall garage door to daylight...

The duct run total length is around 27 ft. with 3- 90 deg. ells being used, so knowing the dryer would not vent properly, the contractor installed the in line booster fan I linked below. ....

I have replaced 3 of these fans thus far in 5 years as I suppose they burn out when the inpeller gets full of lint and makes it drag. Plus the long vent line is making the attendant use too long of drying cycles to compensate. ..

What would a solution be rather than just keep buying these $200.00 fans ? Do they make a larger in line 4 inch exhaust fan (120 Volt) that could handle the lint and get more exhaust ? ...

Or, maybe a pre-fan lint collector paired with a larger ex. fan ? How does one know if they get too much CFM exhaust for the dryer (residential grade) to be able to dry properly ?

I can't believe an architect designed the laundry room this way.

Thanks, Greg



http://www.grainger.com/product/FANTECH-Inline-Centrifugal-Duct-Fan-5C516?searchQuery=5c516

 

[danski0224]

Dryer-Ell

http://www.inovatetech.com/

 

[rlitman]

Dryer-Ell

http://www.inovatetech.com/

That's a start. In metal ducting, you can swivel the sections of a swivel elbow to get it to be 45 degrees. Put two of these together and you have essentially the same thing. A soft elbow that doesn't restrict flow as badly.

Is the vent line made from corrugated aluminum? Switching to a hard duct will be a great improvement on airflow too.

That duct booster is fine for a bathroom fan. Not for a dryer. Get rid of it. That's a recipe for burning your building down. Even with regularly scheduled lint cleaning, and even if you added an additional lint trap to the line before it.

Can the duct be re-routed? Perhaps through the roof?

Is it a front load washing machine? They can spin out more water from towels (especially ones with the higher speed spin), so drying takes less time.

 

[volleyball]

I vote for the front loading dryer. I would also go to a 6 or 8" duct to reduce pressure.
What about putting in some drop legs that would catch lint and drop it down to a clean out?
I assume most duct is not flex.

 

[Super Sport]

I still can't find a way that dryer-ell does anything [we have one] except allow clearance between dryer and wall. Is there another value to it?

That company has several products on that page. You're referring to one that is different than the dryer-ell, which is a type of 90 degree tubing.

 

[DenisG]

http://texastelehack.blogspot.com/2012/12/perils-of-vertical-roof-terminating.html

What's wrong with a short straight horizontal run right through the garage wall?

 

[rlitman]

Depends if there is an available outside wall, but I'm inclined to agree. That lintalert in your link looks like a great idea.

 

[safetyman665]

Why not try a dryer vent lint trap and vent the exhaust right next to the dryer? No need for an elaborate venting setup if you use one of those.

http://m.acehardware.com/product/index.jsp?productId=1273083

 

[danski0224]

So, I guess I misread the initial post, and still haven't based on two other posts, the idea of the idea. Is this about a constriction behind the dryer or the total length run of the tubing being many feet?

I still can't find a way that dryer-ell does anything [we have one] except allow clearance between dryer and wall. Is there another value to it?

A typical residential dryer has a duct limit of 20 feet. Says so right in the instructions.

A typical 3" radius 4" adjustable elbow, when used in a dryer duct, has an equivalent length of 5 feet. This is also in the instructions, and it is also a rule that code officials use.

So, in the OP's installation, there is 15 equivalent feet of duct just in elbows, NOT including any straight pipe.

The OP claims to have 27 feet of duct, excluding elbow equivalencies. The number is really 42 feet in the eyes of the code official and per the installation instructions. Therefore, the dryer is not vented properly.

Those Dryer-Ells have been tested and approved to have a 0 (zero) equivalent feet penalty. The company that sells them has stickers to buy to inform code officials.

If there is room to install them (or, make the room to install them), it will likely help with dryer venting.

Sourcing 10' lengths of 4" pipe in either snaplock or spiral type will minimize seams, which will help.

Commercial dryer booster fans are typically mounted at the end of the run, on a roof or wall, for accessibility.

 

[danski0224]

Why not try a dryer vent lint trap and vent the exhaust right next to the dryer? No need for an elaborate venting setup if you use one of those.

http://m.acehardware.com/product/index.jsp?productId=1273083

Awesome idea for gas dryers.

You get a whole chitload of moisture, dust AND carbon monoxide.

 

[Hpozzuoli]

That's much too long a run for that diameter. At home I run 6" for 5 feet. At my stores I have 12" going no more than 8-10 depending on location. With that much pipe there has to be a lot of lint build up somewhere in there. You would need a chimney brush to clean that length if that would even work. Standard dryer brushes might be too short and flimsy

 

[gregtwojeeps]

Dryer-Ell

http://www.inovatetech.com/

Good store ^^^ to know, the lint alert is interesting.... thanks

It is not a pro gym, just a large "wellness" workout room for the office people, so it has a low budget M&R budget.. It is a "front loader" dryer but not the new age type...

It has a 4 inch heavy duty metal duct all the way, the type that has the metal cord spiraled around it...

There is a mechanical room right behind the dryer, no way to vent the dryer out of the back of it to get to an exterior wall...

The laundry room/garage is in the basement so it has finished offices above it, even if it was boxed/chased to hide it going through a office, it is 32 feet to the roof from the garage floor. Concrete floor also to penetrate...

I investigated the duct layout again before I left work. I can re-route the duct and get rid of two of the short radius 90 deg. ells, but would still have one short radius ell out of the back of the dryer, plus one long sweep to turn away from the wall and get it out on to the ceiling joists over to the exterior wall . I would have to core another exit hole through the exterior cinder block/brick wall and terminate with endcap/damper... yuck

I would probably still end up needing a booster fan though, because even with the proposed new routing I came up with, the duct run will consist of one short radius ell, one long sweep ell and 18 ft. of straight run duct.


On edit: It is a electric dryer and the ACE lint filter above looks appealing but the cleaning of that would be another job added to my responsibilities to remember to do daily. I need a shorter list now, like my memory.

Danski, good idea, where could I find a exterior mount booster exhaust fan for the dryer ?

 

[danski0224]

The laundry room/garage is in the basement so it has finished offices above it, even if it was boxed/chased to hide it going through a office, it is 32 feet to the roof from the garage floor. Concrete floor also to penetrate...

I investigated the duct layout again before I left work. I can re-route the duct and get rid of two of the short radius 90 deg. ells, but would still have one short radius ell out of the back of the dryer, plus one long sweep to turn away from the wall and get it out on to the ceiling joists over to the exterior wall . I would have to core another exit hole through the exterior cinder block/brick wall and terminate with endcap/damper... yuck

Going up probably introduces fire chase issues.

A "Blue Boar" carbide hole saw goes through cinderblock and brick like a hot knife through butter.

 

[danski0224]

where could I find a exterior mount booster exhaust fan for the dryer ?

There are also different style fans, like this: http://www.hvacquick.com/products/r...ng/dryer-booster-fans/tjernlund-dryer-booster

External kit is on this page, part number RVF4XL-DB10: http://www.hvacquick.com/products/r...ing/dryer-booster-fans/fantech-dryer-boosters

Google is your friend.

You are on your own for specs and servicing.

 

[gregtwojeeps]

There are also different style fans, like this: http://www.hvacquick.com/products/r...ng/dryer-booster-fans/tjernlund-dryer-booster

External kit is on this page, part number RVF4XL-DB10: http://www.hvacquick.com/products/r...ing/dryer-booster-fans/fantech-dryer-boosters

Google is your friend.

You are on your own for specs and servicing.

Thanks a lot Danski, the unit you have linked to looks like it would do just what I need. And it is only a few bucks more expensive than the plastic Grainger fan. I REALLY did not want to re-route this dryer duct but will get the long sweep ells also. to all that helped out here ! ,

 

[danski0224]

Grainger is just a B2B distributor. Dayton is their private label.

You have to know what you need, and maybe they will have it... maybe not.

Your plastic Fantec unit is nothing special, but someone outside of the ventilation industry may not know that.

 

[Rookie2]

I see that on the Grainger site but it didn't say "no clog" guarantee in their description. great item !

 

[volleyball]

It is a "front loader" dryer but not the new age type...

Not dryer, a front load washer. The spin cycles cuts the amount of water in half.
So less drying time, means less lint. A few booster pays for it.

 

[DenisG]

Here's a link to specs for exhaust venting for a commercial laundry: goo.gl/upkApA

 

[pseudorealityx]

Using and cleaning your lint filter prior to the booster fan is the solution.

Like anything else, why are you waiting for it to be damaged beyond repair before you even look at it? 15 mins, once every 6 months would solve your problem.

 

[Jackfre]

Check this out

http://www.tjernlund.com/dryer_booster.htm

 

[sands35]

Post dryer filters that are used where I work (biggest white good manufacturer in the US)

http://www.fantech.net/DBLT4W_enus-46000.aspx

They keep the duct clean so it works better.

 

[LS6 Tommy]

If you ask too many questions about the gym in a business you'll find that commercial rules likely apply and likely a commercial dryer and that $10k plus expense along with the maybe 10" vent it requires and it can't be put in a garage due to new regs.

X2. Plus, You can't have the dryer vent (or any exhaust) next to any opening like your garage door... As previously stated, the entire system is WAY off from code spec. You need to shorten the run, period.

Tommy

 

[safetyman665]

Awesome idea for gas dryers.

You get a whole chitload of moisture, dust AND carbon monoxide.

Excellent point. I assumed the OPs dryer was an electric.

 

[mrobins297aaa]

be careful of increasing the size of the ducting, when you increase the size of the duct you slow down the air. you have to have a min amount of velocity on the air to move lint, I can't remember exactly but i think its around around 1500 feet per minute.

also another thing don't forget about make up air, i don't know how small or tight the room/garage you have the dryer in but if its tightly sealed you need a way to replace the air the dryer is pulling from the room.
like danski said the fan should go on the end, thats the way we always did commerical systems.

 

[mrobins297aaa]

Check this out

http://www.tjernlund.com/dryer_booster.htm

this looks like a much better choice than those inline fans.

not to get to technical but if you read the spec's on the fan it says 4" inlet and 160 cfm so outlet velocity is 1839 feet per minute.

the formula is: Area of the duct (in sq feet) x feet per minute (velocity) = CFM

in this case 4" =.087 sq/ft so 160 cfm / .087 = 1839 fpm

changing the duct size to 6" reduces the fpm (velocity) to around 800 fpm to slow for moving lint.

you have to keep in mine that you also have to have a fan capable of developing the velocity you need to push/pull the air.................none of those inline fans develop enough pressure to do that.

 

[mrobins297aaa]

At work we have a gym where a LOT of towels are used that the owner maintains. The architect/builder put the washer /dryer in the one car garage out of the way and there is NO physical space to move the W/D elsewhere, or I would have done so already. ...

The mechanical contractor that installed the 4 in. round metal vent for the dryer had to run it up the wall about 9 ft. and then across the steel ceiling bar joists. He exited the vent duct out through the 8 in. cinder block and brick, right above the 10 ft. tall garage door to daylight...

The duct run total length is around 27 ft. with 3- 90 deg. ells being used, so knowing the dryer would not vent properly, the contractor installed the in line booster fan I linked below. ....

I have replaced 3 of these fans thus far in 5 years as I suppose they burn out when the inpeller gets full of lint and makes it drag. Plus the long vent line is making the attendant use too long of drying cycles to compensate. ..

What would a solution be rather than just keep buying these $200.00 fans ? Do they make a larger in line 4 inch exhaust fan (120 Volt) that could handle the lint and get more exhaust ? ...

Or, maybe a pre-fan lint collector paired with a larger ex. fan ? How does one know if they get too much CFM exhaust for the dryer (residential grade) to be able to dry properly ?

I can't believe an architect designed the laundry room this way.

Thanks, Greg



http://www.grainger.com/product/FANTECH-Inline-Centrifugal-Duct-Fan-5C516?searchQuery=5c516

we did the macomb county jails laundry exhaust system and they had a three commericial dryers that we connected to a 20" header that went into a lint collector just before it left the room, it was basically just a box with a in an out connection, based on the same principle of a shop vac, the air comes in and because of the larger size of the collector the velocity drops way off and so does the lint to the bottom of the collector.........after it left the room it went 140' across the parking garage to a utility set fan and then out the wall.

i don't know why you couldn't build something along the same lines, just a box with with two 4" connections in it, maybe even a filter in the middle between the openings, just make sure its big enough to really slow the air down.

you still need a booster fan

 

[gregtwojeeps]

There are also different style fans, like this: http://www.hvacquick.com/products/r...ng/dryer-booster-fans/tjernlund-dryer-booster

External kit is on this page, part number RVF4XL-DB10: http://www.hvacquick.com/products/r...ing/dryer-booster-fans/fantech-dryer-boosters

Google is your friend.

You are on your own for specs and servicing.

Update: I ordered the fan in the link above and re-routed the duct run to reduce the use of the 5 - 90 degree elbows it had in it. With my new 4 inch duct routing and using the commercial grade duct, I just needed 3 ells...

I used long radius ells purchased from my local sheet metal shop. The whole system is really venting stronger as it should and the new exhaust fan is hand downs better than the Grainger unit it had. Thanks to all for the guidance.

 

[rlitman]

Excellent. Now tape a sheet of paper that shows the install date, and reminds you when to do the next duct cleaning/inspection.

 

[Jackfre]

I'm glad that worked out for you, but the real story will be told in a couple weeks when you drop the fan to check/clean the blades on the fan. I don't know if you watched the video at the Tjernlund site but dryer vents are a really hostile environment and fan blades load up quickly. Hopefully your fan blades are of the material handling type. Please let us know how this works out performance wise over time.

 

[gregtwojeeps]

I am going to let the chimney cleaning service that maintains the facilities flues, to clean the dryer duct as needed. He uses a rotating brush sized to the duct on a long extendable motor driven flexible shaft, while a huge vacuum unit ***** the trash out.