CLA Connect Open Forum

Dryer venting and seals

  • 1.  Dryer venting and seals

    Posted 01-13-2018 14:47
    Purchased new dryers in 2017.  The dryers are Wascomat stackable dryers there are 8 stackable or 16 in that row. There is new venting above the dryers leading to the roof inside the laundromat. Should this installation also include new dryer venting on the exterior?  If so, what should it include?  

    Had photos taken after Hurricane Irma and noticed that the venting pipes are the old vent pipes. 

    What seals do you recommend to make the vents water tight to prevent rain from pooling in the dryers below?

    Your insight is most appreciated

    Cassie Demetsky
    Coronado Laundromat


  • 2.  RE: Dryer venting and seals

    Posted 01-13-2018 15:26
    Edited by Curt Harrington 01-13-2018 15:41

    It sounds like you have exhaust and no make up air. If that is the case you will be taking air from the conditioned space. Not good for many reasons. I do not remember the formula for that but yes you must have makeup air from behind the dryers. A bunch.
    Rain prevention. Candy-cane. Two 90 degree elbows above the roof so exhaust (or intake) faces down.

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    Curt Harrington

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  • 3.  RE: Dryer venting and seals

    Posted 01-14-2018 12:00
    The formula is generally 1 sq ft per pocket for 30 lb dryers.
    1 .5 - 2 sq ft per pocket for 45 lb and 50 lb dryers, and 2 sq ft for 75's.
    That means you need At Least 2 sq ft for a stack 30 lb dryer.
    More is always better.

    Too little make-up air for a dryer Will (not can, Will) lead to all sorts of undesirable consequences.

    The make up air needs to come from somewhere, and it will take it from the easiest places.

    It Will suck it out of you air conditioned spaces, so now you are spending $$$'s to cool the spaces, and $$$'s to heat up that nice cooled air to 180* into the dryer.

    It Will suck the air from joints in your dryer and venting, along with the lint, and coat everything in behind the dryers with a nice thick flammable layer of lint and dust.

    It Will take air from the rear space, and cause the dryers to not ignite, heat, or work as they should.
    This might drive you or your tech crazy, because when ever he is back there the access door is open, providing enough air, as long as he is looking at it.
    It quits working when he closes the door.

    By the way this is one way to tell if you have too little make-up air.
    Turn on all your dryers.
    Open the access door.
    Now slowly nudge it closed.
    At some point the door will suddenly slam shut.
    If it doesn't you do have enough make-up air.
    If it slams shut you do Not have enough make-up air.

    As far as the outside venting;
    Since it is older, one thing to check is to make sure that the venting from the dryer to the roof Inside is the same size as the dryer venting Outside.

    Believe or not there are Some installers that take "short-cut" (shocking I know!)

    I have found all to many times where and installer has adapted a larger vent down to a smaller existing vent. (ie; 8" from the dryer to roof- 6" original from the rooftop out)


    This will make you wonder why your brand new dryers work fine when only one pocket is running, but won't dry as fast with two pockets running.


    In my installations I use a "roof-jack", which is that cone shaped piece on the roof, around the vent pipe.
    I seal the cone to the roof with a generous amount of roofing sealant/tar (Henry's)
    I seal the top of the cone to the pipe with more sealant, then I use a Storm Collar around to vent just above the cone. Smear a generous amount of sealant around the vent pipe, and slide the collar down onto/into the sealant.
    On the top of the vent I use 2 90* adjustable elbows, with the last end joint of the elbow adjust straight to a 45* angle.
    Seal all the joints with a good sealer.

    Never had a leak yet.

    ------------------------------
    DAVID CHAMLEE
    Service Technician since 1986
    and sometimes Laundromat Owner
    CCR
    Santa Barbara, CA
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  • 4.  RE: Dryer venting and seals

    Posted 01-14-2018 15:11

    Hello David,

    I have a question for you.

    You mentioned the make-up air formula is generally that for 30 lb dryers 1 sq ft (929 sq cm), per pocket and for 50 lb dryers 1.5 – 2. sq ft (1,394 -1,858 sq cm) per pocket.

    I always had this debate with the technician from the service department of my equipment dealership. Here is an example:

    5 ea. 30# stack equals 10 pockets times 1.5 sq ft per pocket equals 15 sq ft make-up air

    2 ea. 50# stack equals 4 pockets times 2.5 sq ft per pocket equals 10 sq ft make-up air

    For a grand total of 25 sq ft

    And he can not come with a straight or supported answer.

    I told him that as long as you have a total opening or at least 25 sq ft  opening for make-up air for the whole 7 stack dryers / 14 pockets to the outside of the bulkhead / building dryer area, (The Mexico City average yearly temperature typically varies from 43°F to 80°F and is rarely below 37°F or above 86°F although we are an altitude of at 7,350 ft) it does not matter that this is a single opening of 4" by 6 1/4 " or 7 openings 3.6 sq ft each or either 14 openings (7 at the top and another 7 at the bottom of each stack dryer) 1.8 sq ft each, the total amont of make –up air requierd as manufacturer specifications is being satisfied.

    He insists that you MUST have a total of 14 openings one in front for each pocket (7 at the top and another 7 at the bottom of each stack dryer) of 1 3/4 sq ft each.

    He also does not accept the higher you go above sea level, the less oxygen content in the air. That for elevations above 2,000 feet (609 mts), dryer´s BTU´s input ratings should be reduced 4 percent for every 1,000 feet (305 meters) above sea level. 

    7,350 – 2,000 = 5,350 ÷ 1,000 = 5.3 x 4% = 21.4% x 90,000BTU´s/h (26.4 kW) dryer rated Gas Usage 60Hz Model per tumbler (manufacturer specifications), you ought to have 19,260 BTU´s lost due high altitude for an net dryer efficiency of 70,740 BTU´s or virtual gas usage of 109,260 BTU´s

    That if your dryers are working with LPG gas instead NG gas you MUST have a propane gas kit with a reduced gas orifice to ensure complete combustion and that the incoming gas temperature or the barometric pressure from the gas storage tank has little to none to do with the altitude.

    That 1 litre of LPG gas which has ± 24,200 BTU´s High Heating Value then that litre is derated to ±19,021 BTU´s for which I should charge more for the full drying cycle and not as he says that I am manipulating the information and using it as an excuse to jack up my vending prices every quarter even the gas supplied by the city is increasing prices every month. Current cost / price for January 2018 is 10.40 MxP per litre or $ 0.54 USD per litre / $ 2.05 USD per gallon.

    What is your expert opinion as ServiceTechnician since 1986 and sometimes Laundromat Owner regarding the number of openings, the size and the position of such opening.?



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    Miguel A Gonzalez
    DF
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  • 5.  RE: Dryer venting and seals

    Posted 01-14-2018 16:23
    Edited by Larry Adamski 01-14-2018 16:25
    Miguel,

    Your math seems off ... just a bit.  a 30 lb. dryer pocket requires 1 sq ft of (free) makeup air opening.  So five 30 lb. stacked dryers (10 pockets) would require 10 sq ft of makeup air opening.  A 50 lb. pocket requires 1.5 to 2 sq ft of makeup air opening.  So two 50 lb. stacked dryers (4 pockets) would require up to 8 sq ft of makeup air opening.  Together the 14 dryer pockets would require 18 sq ft of makeup air opening - not 25 sq ft.

    You mentioned the make-up air formula is generally that for 30 lb dryers 1 sq ft (929 sq cm), per pocket and for 50 lb dryers 1.5 – 2. sq ft (1,394 -1,858 sq cm) per pocket.

    I always had this debate with the technician from the service department of my equipment dealership. Here is an example:

    5 ea. 30# stack equals 10 pockets times 1.5 sq ft per pocket equals 15 sq ft make-up air

    2 ea. 50# stack equals 4 pockets times 2.5 sq ft per pocket equals 10 sq ft make-up air

    For a grand total of 25 sq ft
    Miguel A. Gonzalez,  01-14-2018 15:10
    Using your 21.4% loss in gas efficiency due to the 7,350 ft altitude of Mexico City would make the effective size of your 90,000 btu dryer stove about 70,740 btu.  My 30 lb. Huebsch dryers are rated at 73,000 btu and still require 1 sq ft of makeup air.  So it would seem logical that, even at Mexico City's 7,350 ft elevation, 1 sq ft of makeup air would be required on your down-rated dryers.  Now, I don't think your dryer burns more gas at that high elevation; I think it burns less gas to compensate for a lower barometric air pressure.  I think your dryer stove has a smaller orifice in the burner to accomplish this.

    Does this mean your dryers don't dry as well at your high altitude?  Not necessarily.  Since water boils at a lower temperature as barometric pressure decreases (or altitude increases), water may evaporate off clothing just as well at your higher altitude with your 21.4% less effective dryer stove as it does at my laundromat which is 620 ft. above sea level with a fully effective stove.

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    Larry Adamski
    Muskegon Laundromat
    Spring Lake MI
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  • 6.  RE: Dryer venting and seals

    Posted 01-14-2018 19:32
    Edited by Miguel A. Gonzalez 01-14-2018 19:45

    Hello Larry,

    Sorry but my math not seems to be off . . . check my wording.

    As I clearly stated " I always had this debate with the technician from the service department of my equipment dealership. Here is an example:

    5 ea. 30# stack equals 10 pockets times 1.5 sq ft per pocket equals 15 sq ft make-up air

    2 ea. 50# stack equals 4 pockets times 2.5 sq ft per pocket equals 10 sq ft make-up air "

    I did not based my math in 30 lb. dryer pocket requires 1 sq ft of (free) but 1.5 sq ft per pocket and

    50 lb. pocket requires 1.5 to 2 sq ft of makeup air opening but 2.5 sq ft per pocket as you assumed

    So, the total in this particular presented example was / is a grand total of 25 sq ft and not 18 sq ft as you calcaulated.

    With all due respect.

    " The 21.4% loss in gas efficiency due to the 7,350 altitude Mexico City from the effective size of the 90,000 BTU´s dryer stove to about 70,740 BTU´s has nothing to do with your 30 lb. Huebsch dryers rated at 73,000 BTU´s and still require 1 sq ft of makeup air "  

    One thing is that you either need a virtual / assumed gas usage of 109,260 BTU´s for a 7,350 altitude Mexico City to maintain manufacturer's normal input rating measured in the 90,000BTU´s/h (26.4 kW) Dryer Rated Gas Usage at 208-240 Volts / 60 Hz / 1 Phase / 3 wire + ground wiring or in fact the 90,000BTU´s/h stove burning / consumption becomes 70,740 BTU´S HEATING VALUE with any size of the make-up air required or size opening. Either is 1 sq ft or 2.5 sq ft as long as you keep or exceed the generally formula mentioned by David.

    One thing is the gas needed to achieve the mentioned 90,000 BTU´s/h and another the make-up size opening for the adequate amount of intake fresh air ( NOT air conditioned) from behind / coming from outside the dryers in order to heat the air going inside the dryer  to be heated and dry the clothes as they tumble (it's similar to a hair dryer; it pulls the air in through a vent, heats it, and spits it back out). Such openings can be also either set behind / back the dryer bulkhead or placed in the roof that allowing outside air to reach the back of the dryers by pipes.

    Therefore there is no direct relationship between your Huebsch dryers rated at 73,000 BTU¨s/ requiring 1 sq ft of makeup air.
    1 sq ft ÷ 73,000 BTU´s = 0.00000136986 and 1.5 sq ft ÷ 90,000 BTU´s  = 0.00001666667 ratios

    One thing is the rated gas usage measured in The British Thermal Unit (BTU) which is a traditional unit of heat and it is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit and the amount of fresh airflow measured in cubic feet per minute (cfm or M3/min) to be fed from the outside through an opening that is leaving the dryer during the drying / tumbler / heating / evaporating of water in clothes in the cylindert and thru the vents.

    Units of BTU´s or Heating Value has nothing to do with lack of fresh air "suffocating" and have no air to heat and dry the clothes. Or lack of make-up or air opening size / requirements.

    Apples to Oranges. Two diffrenet things that are fundamentally different and therefore not suited to comparison.

    Yes, You are right. " My dryer DOES NOT burn more gas at that high elevation ", what happens is that the gas burned at an altitude of 7,350 feet above sea level generates a lower amount of calorific / heating value due to lack of "pure" oxygen and therefore the combustion is less perfect for what is needed a kit in for two things.

    1.- For the Liquefied Petroleum Gas (LPG) that I use and  2.- For Altitude Compensation. To achieve a more / better combustion. My dryers generate about 70,740 BTU´s Heating Value intead of the 90,000 BTU´s rated according to tables.

    My dryers dry perfectly. Remember that Mexico City average yearly temperature typically varies from 43°F to 80°F and is rarely below 37°F or above 86°F; with 32.3 inches in annual rainfall;  humidity 12.9%;  dew point 12.2 oF; barometric pressure 512 mmHg;  the wind speed gust at 4.3 miles per hour  and air pollution an UNHEALTHY 127 Air Quality Index (AQI) Nitrogen Dioxyde (NO2). I might have and advantge over you in Cold / Winter Michigan.

    One more thing to think about. Here in Mexico City we do not need / use ever HVAC at all. Is not that a beauty?

    That is the reason because I have set my dryres in full drying cycle mode of 32 minutes divided as following:

    • 19 (nineteen) minutes BURNER ON 65%
    • 10 (ten) minutes and BURNER OFF 35%
    • 3 (three) minutes cool-down
    • High temperatura at 190oF / 88oC
    • Medium 170oF / 76oC as pre-established start-up / initial temperature and from where there customers can either go high or low as they please at the very same price. $ 35 MxP or $ 1.82 USD as today exchange rate
    • Low 150oF / 65oC        
    • Delicate 130oF / 54oC

    Have you visited a high altitude city? Sure you have. You are a licensed pilot. What happens to your respiratory system? At High-altitude environments you have adverse effects on the normal functioning body because of the change in barometric pressure, lack of "pure" oxigen, high levels of CO2, which causes a decrease in the amount of oxygen to burn / metabolize leading to hypobaric hypoxia, you have adverse effects on heavy body weight sensation, muscle structure, exercise capacity, mental functioning, sleep quality, dizziness, and fainting. You breath faster and deeper, generate more carbon dioxide (CO2). But your lungs size do not change.

    Have you  ever exercise / walk / fly at sea level and above 7,350 ft? What does your airplane has experienced at different altitudes? Do you consume more or less petrol? Do you get faster or slow?

    My LPG gas litre instead of yielding 24,200 BTU´s only outputs ±19,021 BTU´s. 21.4% less.

     

    As a favor to me. Can you teach me how to do the following


    Thanks in advance



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    Miguel A Gonzalez
    DF
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  • 7.  RE: Dryer venting and seals

    Posted 01-15-2018 13:47
    Miguel,

    According the Manufacturer's Specifications The 1 sq ft per dryer pocket is a Minimum Requirement. More is better.

    I suspect your Distributor's logic with having one opening behind each dryer is to allow easy air access to the dryer.
    Because, of course, "Air Doesn't Move." lol.
    There is some logic to this approach, but his Is faulty. As you surmised.
    See my previous post about dryers sucking air from wherever they can.
    It's not a Bad idea, but it isn't "the only way", nor even the most desirable way either.

    You are correct to say that 1ft x 1ft = 1 sq ft.
    Also 6" x 2 ft = 1 sq ft., as does 3" x 4 ft. = 1 sq ft.
    These would all be acceptable, under the manufacturers specs.
    Where it gets more interesting, with regards to openings, is the subject of Air Flow.

    Let's Assume you have 10 pockets in your dryers (10 singles or 5 stacks)
    10 dryers x 1 sq ft per dryer = 10 sq ft.
    10 openings @ 1 sq ft each would = 10 sq ft.
    As would 1 opening 1 ft high x 10 ft long.
    As would 1 opening 2 ft high by 5 ft long.
    (now watch this)
    As Would 1 opening 3 ft x 3 ft !
    Wait you may say, that's only 9 sq ft !? 
    That's where Air Flow overcomes Sq Ft​.
    (Friction and Restriction, as they say)
    Think of 10 - 1" holes in your bathtub vs. 1 - 10" hole. 

    This is where both of your calculations are crossing paths with each other.
    Neither is 100% right, nor 100% wrong.
    They are both accurate, but for different reasons, and approaches.
    Of course you also need to take into account the louvers, hardware cloth, and any other restrictions.
    That's why I Always round-up, or even double the Manufacturers Specs, when possible.

    In one Laundromat I built, the owner has 15 stack 30lb dryers, and 3 stack 45 dryers.
    15 x 2 x 1 = 30 sqft.
    3 x 2 x 1.5 = 9 sqft.
    Total 39 sqft. round up to 40 sqft.
    For this owner I built 4 Rooftop vent risers, each 30" x 60", with louvers on all four sides.
    30" (2.5) x 60" (5 ft) = 12.5 sqft per riser x 4 risers = 50 sqft intake opening in the roof.
    When you take into account the Airflow that can enter a hole that size, it is excessive, even when you subtract the louver restrictions.
    Too much air available to the dryer is better than not enough.

    I have never had Any Air Flow related problem in his place.
    There is practically No Lint or Dust build up behind his dryers.
    And because the Vents are correctly sized and placed, I have Never had to Clean any of them!
    Actually, I've Never had to clean Any of the vents on Any of the dryers I've installed in the last 30 years.
    Size the vent correctly, Design the vent correctly, Install the vent correctly, and the moving air coming out of the dryer keep the vent walls clean. The lint never even has a chance to deposit on the sides of the vents.

    ------------------------------
    DAVID CHAMLEE
    Service Technician since 1986
    and sometimes Laundromat Owner
    CCR
    Santa Barbara, CA
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  • 8.  RE: Dryer venting and seals

    Posted 01-15-2018 17:27
    I also have one mat with a riser on the roof with openings on the side. I have to say this is the optimal way to go. Compared to my mats with make up air on the back wall this is much better. Dryers get plenty of air. Because a cross draft is created, you don't get as much cold air behind the dryers when not in use. Same in the summer. Behind the dryers stays comfortable. Saves on Hvac.

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    Chris Mirisciotta
    Store Owner/ Employee
    Canon Coin Laundry
    Canonsburg PA
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  • 9.  RE: Dryer venting and seals

    Posted 01-16-2018 06:36
    Thank you so much for your professional advice. I will try to print these instructions so that I can have it to study. Really  appreciate the information to share.

    Kathleen Demetsky
    Coronado Laundromat
    Naples, FL.


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    KATHLEEN DEMETSKY
    Store Owner/ Employee
    CORONADO LAUNDROMAT, LLC
    Naples FL
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