What size unit is good for my application? How to choose the right AC?
Keep a pen and paper next to you and write down answers to below questions first. Then move to step 2.
A. First question is how many air handlers (indoor units) would you need?
Answer to this comes from the number of rooms you want to cool or heat. Remember since this is ductless, you will need ONE air handler per room. But if your kitchen, dinning area and living room are all connected and open to each other, in that case you will need just ONE for this entire area. But if your dinning room has walls around it with only a door size opening from the kitchen, in that case you may want to put ONE in kitchen and ONE in dinning room.
B. Are the rooms well insulated? If not we will call it "Situation B"
C. How many windows you have in each room? Are these energy efficient windows? (single pane or double pane windows). If you have 2-3 windows in one room and they are single pane windows that are not energy efficient, we will call it a "Situation C"
D. Then you need to know the height of your ceiling. Is it a regular ceiling or more than 10 ft high? If it has a high ceiling of 15 or 20 ft, we will call it is "Situation D"
E. Do you have any heat generating source in these rooms like sunlight, equipments, computers/server or kitchen etc? If yes, we will call it a "Situation E"
F. Last but not the least you need to know the sq ft of each room.
Once you have the above info, it gets simple then. Below table will help you decide and give you a approx. estimation of what you really need.
Please consult your HVAC installer before making your decision. Below info can help you decide, but it cannot be guaranteed accurate under different circumstances.
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BUY 9000 BTU Split AC?
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BUY 12000 BTU Split AC?
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BUY 18000 BTU Split AC?
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BUY 24000 BTU Split AC?
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If your room is Upto 300 sq ft without any bad situation B, C, D or E (Example: The room is 275 sq ft, house is well insluated, has double pane windows, it is a bedroom with regular ceiling. This means there is nothing wrong with the room conditions)
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YES
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NO
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NO
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NO
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If your room is Upto 300 SQ FT with either one of the above bad situations B or C or D or E (Example: the house is well insulated and has energy efficient windows, but it is a sun room with lot of windows and is 250 sq ft)
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MAYBE WILL WORK
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YES
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NO
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NO
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If your room is Upto 300 SQ FT with WORSE SITUATION (Example: the house is not insulated and has old windows that are not energy efficient)
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NO
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YES
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MAYBE (If it is a restaurant kitchen for example)
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NO
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If your room is between 300 - 500 sq ft without any situation B, C, D or E (Example: The room is 475 sq ft, house is well insluated, has double pane windows, it is a bedroom with regular ceiling. This means there is nothing wrong with the room conditions)
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NO
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YES
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NO
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NO
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If your room is between 300 - 500 SQ FT with either one of the above situations B or C or D or E (Example: the house is well insulated and has energy efficient windows, but it is a sun room with lot of windows and is 450 sq ft)
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NO
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MAYBE WILL WORK
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THIS IS BETTER OPTION
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NO
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If your room is between 300 - 500 SQ FT with WORSE SITUATION (Example: the house is not insulated and has old windows that are not energy efficient)
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NO
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NO
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YES
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MAYBE IF THE SITUATION WAS WORSE
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If your room is between 500 - 700 sq ft without any situation B, C, D or E (Example: The room is 675 sq ft, house is well insluated, has double pane windows, it is a bedroom with regular ceiling. This means there is nothing wrong with the room conditions)
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NO
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NO
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YES
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NO
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If your room is between 500 - 700 SQ FT with either one of the above situations B or C or D or E (Example: the house is well insulated and has energy efficient windows, but it is a sun room with lot of windows and is 650 sq ft)
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NO
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NO
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YES
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MAYBE
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If your room is between 500 - 700 SQ FT with WORSE SITUATION (Example: the house is not insulated and has old windows that are not energy efficient)
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NO
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NO
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MAYBE WILL WORK
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YES TO BE ON SAFER SIDE
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If your room is between 700 - 1000 sq ft without any situation B, C, D or E (Example: The room is 975 sq ft, house is well insluated, has double pane windows, it is a bedroom with regular ceiling. This means there is nothing wrong with the room conditions)
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NO
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NO
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NO
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YES
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If your room is between 700 - 1000 SQ FT with either one of the above situations B or C or D or E (Example: the house is well insulated and has energy efficient windows, but it is a sun room with lot of windows and is 950 sq ft)
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NO
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NO
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NO
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YES (MAYBE A 30,000 BTU NEEDED)
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If your room is between 700 - 1000 SQ FT with WORSE SITUATION (Example: the house is not insulated and has old windows that are not energy efficient)
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NO
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NO
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TWO 18000 BTU'S NEEDED A TOTAL OF 36000 BTUS
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NO
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For room more than 1000 sq ft, example it is a office space with 1500 sq ft, you will need more than one unit in that one big room for better circulation. So you can buy a 2-3 sinagles zone units or dual zone, trizone or a quadzone depending upon how big the room is as per above calculations.
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Now once you have decided how many units you need, it is time to see what features you want. Low Ambience Feature
For example if you live in New York where the temperature goes below 15 deg quiet a few times in a year and if you need this AC unit to do the heating job as well in the winter time, in that case DO NOT buy the standard SEER 13 without Low Ambience. You need the unit that has Low Ambience operation as they can produce heat in temperature as low as minus 4 deg or zero deg depending upon which unit you end up buying. YMGI/LG/Friedrich/Haier for example have units that produce heat in temperature as low as zero deg
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