The formulas we have all heard and still hear from Sales people is NOT correct and will cost far more on the electric bill. Note this one example of a formula from a Sales staff:
Length of room multiply Width of room multiply by 100 equals BTU size.
10 feet X 10 feet = 100; then X 100 = 10,000 BTUs.
That formula above is WRONG.
A ten by ten room would most likely need only a 5,000 BTU air conditioner. Worst case - still only 6,000 BTUs.
The above formula only sells inventory and will double your electric bill, PLUS make the room CLAMY!
This is because the AC unit is double the size needed, thus the compressor will cycle on and off, on and off, leaving the room sticky and clamy. Basically the AC unit can never get rid of the Humidity in the room because it is oversized.
For each room the Sisters live in use the W.H.I.L.E. formula.
Proper sizing of a ROOM air conditioner is dependent upon the cooling load, or the amount of BTU/HR the air conditioner must remove from the room in order to maintain the desired temperature.
(BTU/HR means British Thermal Units Per Hour)
The cooling load can be determined by using the W.H.I.L.E. formula then Divided by 60 as shown below:
W = Width of room
H = Height of room
I = Insulation value in the walls (Use the Number 10 for WELL INSULATED and 18 for POORLY INSULATED)
L = Length of room
E = Exposure (Which direction the longest outside wall faces. North use 16; East use 17; South use 18; West use 20)
W x H x I x L x E divide by 60 = BTUs needed.
NOTE: Since sizes of air conditioners vary in BTU's from one manufacturer to another, always choose the one with the highest E.E.R. that is closest to the BTU size you need. (EER means Energy Efficiency Rating)
For the CLASSROOMS, due to many occupants contributing to a higher index of body heat and very large windows allowing more heat from the sun to be a contributing factor of heat build up, the WHILE formula is not sophisticated enough. The formula needed is very long and very accurate. I will have to make a copy of that page and chart for you.
Any other questions or concerns, just call or email.
Updated Blog Post - From EnergyHotwire.com to GoingTrueGreen.com
Bill Lauto, at GoingTrueGreen.com
International Sustainability and Energy Consultant
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