How to Calculate Needed Tonnage for Air Conditioners
Tonnage is one way to measure the capacity of an air conditioner, with each ton representing the amount of heat needed to melt one ton of ice. More common are British thermal units, or Btu, with each Btu equal to the amount of energy needed to raise one pound of water one degree Fahrenheit. To calculate the the tonnage you need, you will need to know the size of your home in square feet, whether any rooms receive extra sun or minimal sun and how your rooms will be used. Does this Spark an idea?
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Instructions
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1
Approximate the total Btu needed for your home by using a sizing chart that estimates the capacity based on the square footage of your home.
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2
Modify your approximation for any particularly sunny rooms by adding 10 percent to that room's capacity. Use the room sizing chart from the U.S. Environmental Protection Agency to determine how much that room requires. Then multiply this number by 0.1 to determine how much to add.
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3
Subtract 1,000 Btu for each room that is shaded or otherwise gets minimal sun.
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4
Add 4,000 Btu for every kitchen. The requirements are higher for kitchens because of the extra heat generated in them.
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5
Add 600 Btu per person above the second that will live in each bedroom. This does not refer to people who will use a room such as a living room. For example, if five people will share a room, you would add 1,800 Btu.
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6
Total steps 1 through 5. This is the total Btu capacity your air conditioner must have. Divide this by 12,000 to find the tonnage your unit needs; there are 12,000 Btu per ton. For example, if the total was 30,000 Btu, you would need an air conditioner with a capacity of 2.5 tons.
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Tips & Warnings
Buy an air conditioning unit with the Energy Star label because even though it may cost more to purchase it will save you money over the life of the unit and minimize the environmental impact because it is more efficient.
