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.?
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:
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 ratiosOne 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:
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 followingThanks in advance
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