Size is the most crucial factor to consider when choosing the best air conditioning system for your home. The size has nothing to do with the physical features of the AC- it is about the capacity to cool a given footage. Here follows a guide on how to get the right sizing and attain effective cooling.
The Unit Used in Measuring Cooling Capacity
A British Thermal Unit (BTU) measures heat content in all sources of energy. One BTU is the quantity of heat that acts on a pound of water (in liquid form) to raise its temperature by one degree Fahrenheit.
The US Energy Information Administration uses this unit as the standard. BTUs form the basis of calculating the sizes of air conditioning systems used in homes and commercial buildings.
Factors You May Consider When Calculating AC Size
- The total area of the home ( find it by adding the areas of each room)
- The number of people at home. As a rule of thumb, match each person with the capacity to produce 600 BTUs
- Sources of heat in the building, such as kitchens, windows, and doors.
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Ways of Calculating AC Size
Calculating for a Single Floor Area (One Room)
The standard of measurement is 30 BTUs. However, accurate estimations depend on your home location- find out your climate zone and establish its heating factor. Here are some guiding estimates:
Zone 1: 30
Zone 2: 35
Zone 3: 40
Zone 4: 45
Zone 5: 50
Pick the lowest heat factor for illustration purposes. Multiply the area you want to cool by 30. This step gives the minimum capacity that you require. A regular tape measure is enough to establish the length and width of your room in feet.
If the length is 15 feet and width 20 feet, you get area by multiplying 15 by 20. The area here is 300 square feet. The minimum capacity for your room, in this case, is 9000 BTUs per hour. You will, therefore, have to buy an air conditioner of 9,500 BTUs per hour since that is the nearest capacity above 9,000.
You can follow a convenience chart for guidance on which AC to choose.
Calculating AC Size for the Whole House
If the total area is 2000 square feet, with ten windows and three doors facing the sun, use this example:
- Multiply 2000 by 25 to get 50,000 BTU
- Multiply 600 by the number of people (five in our case) to get 3,000
- Multiply ten windows by 1,000 to get 10,000 BTUs
- Assuming each door emits 1,000 BTUs, three will add up to 3,000
- The total is 57,000 BTUs.
Determining the Right Central Air Conditioning Size
Commercial buildings have bigger air conditioning systems as opposed to residences. They use central air conditioners whose measuring capacity is "tonnage."
Tonnage does not refer to the weight of the air conditioning unit. Instead, it is the measurement of cooling ability. One ton cools 12,000BTUs every hour.
You can install a central air conditioning system and borrow from the calculation system adopted in commercial buildings. These air conditioning systems are available for residences provided the cooling capacity does not exceed 5 tons.
How to Calculate Home AC Size in Tonnage
An average American home is about 1500 square feet. Multiply this area by a constant of 30 then divide the result by 12,000. After that, subtract 1.0 to get the needed tonnage. Here is the demonstration:
- 1500 square feet multiplied by 30 gives 45,000
- 45,000 divided by 12,000 equals 3.75
- Subtracting one from 3.75, you get 2.75
Since a slightly larger size is better than the actual or lower quality, round off the figure 2.75) to 3.0. The average home requires a central air conditioning system with 3-ton capacity- the ideal size for most households, not in the arid zones.
If your home falls in the Southwestern part of the country, use the same formula. The only difference this time will be that you do not subtract the constant of one. Rounding off the figure of 3.75 gives you 4.0. In this regard, average-sized homes in the arid climate zones need a 4-ton AC.
An Easier Way Out
As an alternative also, you can use existing AC sizing graphs available online. Your effort here will be to know the average climate of your region. The charts show different zones according to climate with estimated home footage. All you need to do is to locate your zone and home size and mark the corresponding AC size on the chart.
The downside of this method is its generalization of climate conditions. You are looking for the right AC size for your home, yet the chart shows you estimate according to zones. You risk failing to get the right-sized air conditioner for your home in the exact way you want it.
Disadvantages of Choosing the Wrong-Sized of AC
If you install a smaller capacity AC, it will just run but not cool effectively. The air conditioner struggles to reach the temperature you desire in your home. You end up incurring additional energy costs for nothing.
On the other hand, an extremely high capacity AC may be a fast cooler. In the end, however, it does not remove moisture properly. Instead of attaining a cooling effect, it makes your room feel too cold. Besides, such an air conditioner wears out faster than it should.
Every home has its particular cooling requirements. The air conditioner you choose must be optimal for the prevailing conditions. You do not have to pick the one with the exact capacity that calculations give. The rule of the thumb should be to choose a slightly higher size AC.
Having to do calculations can be cumbersome. That is where a professional contractor comes since they have experience. The demanding nature of calculations calls for more professional input than DIY.
With the right information and professional guidance, you may proceed to choose the most suitable air conditioner for your home. Remember, the conditions inside your home are not the same as that of your neighbor.