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Armstrong Air Conditioner Tonnage: Why It Is Necessary And How To Determine Your AC’s Capacity

Armstrong Air Conditioner Tonnage: Why It Is Necessary And How To Determine Your AC's Capacity

Discovering the tonnage of your Armstrong air conditioner is crucial for maintaining optimal comfort. Have you ever wondered how to find the tonnage in an Armstrong air conditioner and what it signifies? Fear not, as we have conducted thorough research to provide you with the answers.

To determine the tonnage of an Armstrong air conditioner, you can refer to the last two numbers in the model code. Divide these digits by 12 to obtain the tonnage. However, it’s important to note that older units may follow a different format, where the capacity is indicated to the left of the dash.

In this article, we will guide you through the process of identifying the tonnage of an Armstrong air conditioner. We will also discuss the importance of selecting the right size AC and understanding the significance of tonnage. Read on for more detailed information.

How to Find Tonnage on an Armstrong Air Conditioner

Armstrong Air Conditioner Tonnage: Why It Is Necessary And How To Determine Your AC's Capacity

In the HVAC industry, tonnage refers to the capacity of an AC unit to alter the temperature of a room. Tonnage is calculated using the British Thermal Unit (BTU).

BTU measures the amount of energy required to raise the temperature of a body by one degree Fahrenheit. One tonnage is equivalent to 12,000 BTU, which is abbreviated to “12” in the model code by manufacturers.

Understanding the tonnage of an Armstrong AC unit is essential for proper sizing in an area. Let’s consider an example with the model code “4SHP16LS136P”:

Tonnage = Last two numbers ÷ 12
= 36 ÷ 12
= 3

Therefore, the tonnage of an Armstrong AC unit with the model code “4SHP16LS136P” is 3, indicating a capacity of 36,000 BTU.

However, for older units with shorter codes like “CJK24S-2C,” determining the tonnage requires a slightly different calculation. In this example, the last two numbers are 24 since there is a dash next to the number 2. Thus, the tonnage can be calculated as follows:

Tonnage = 24 ÷ 12
= 2

Hence, the tonnage of the Armstrong AC unit with the model code “CJK24S-2C” is 2, corresponding to a capacity of 24,000 BTU.

If you are unsure about the numbers and require additional confirmation, you can rely on the RLA (Rated Load Amps) printed on the compressor motor. Simply divide the RLA by 5 or 6, depending on the specific unit. The resulting value will provide an approximate tonnage requirement for your AC. Consult the user’s guide for further instructions on dividing RLA.

Consequences of Not Following the AC’s Tonnage Requirement

Using an AC with an inappropriate tonnage can lead to various issues. It is crucial to select an AC with the correct tonnage to ensure efficient temperature regulation. Let’s explore some potential problems that may arise when using an AC with improper tonnage.

Wasted Energy
Using a lower tonnage AC in a large area will result in a significant energy loss. Keep in mind that an AC unit requires sufficient time to cool down a specific area to the desired temperature.

For instance, a 1-ton unit can effectively cool an area of 600 square feet. To determine the appropriate size of AC required for an area, divide the area by 600. Suppose you need to install an AC unit in a 1,700 square feet area. The calculation would be as follows:

Tonnage = Area ÷ 600
= 1,700 ÷ 600
= 2.83

Hence, an area of 1,700 square feet necessitates a 2.83-ton AC unit. However, since there are no AC units available with exactly 2.83 tonnage, you can opt for the closest tonnage requirement, which would be a 3-ton unit.

Premature AC Malfunction
Running an AC with an incorrect tonnage places strain on its components and motors, leading to premature wear and potential malfunctions.

In the case of an oversized AC, the thermostat may detect temperature changes too quickly, causing frequent motor shutdowns. Conversely, an undersized AC may overheat while attempting to cool the area without adequate breaks.

To prolong the lifespan of your AC, it is crucial to install it in an area that matches its appropriate tonnage. Remember that a malfunctioning motor can be a serious issue for your AC.

Unhealthy Air
Using an AC with an improper size can negatively impact indoor air quality. It can result in either excessive or insufficient circulation of processed air. It is essential to avoid the health risks associated with incorrect AC sizing, especially during hot seasons when dehydration due to extreme heat is a concern.

Armstrong Air Conditioner Tonnage: Why It Is Necessary And How To Determine Your AC's Capacity

Additionally, ensure that the area has proper ventilation as the right tonnage alone may be ineffective in a poorly ventilated space. Enhance ventilation by incorporating fans to facilitate air distribution throughout the area.

Determining the Number of AC Units for Your Home

Most homeowners utilize a single AC unit to cool their entire home, which is generally sufficient. However, it is advisable to perform a proper calculation to determine whether additional AC units are required, ensuring appropriate tonnage coverage for the entire area.

Consider a two-story house with the first floor measuring 500 square feet and the second floor covering 350 square feet. Since a 1-ton unit can cool an area of up to 600 square feet, you can use a 1-ton unit for the first floor. While this may seem oversized for the first floor, it is acceptable since the next available tonnage is 1.5, suitable for areas up to 900 square feet. The lower tonnage option is 0.5, which can cover areas of up to 300 square feet.

However, the 350 square feet area of the second floor falls below the 1-ton unit’s capacity, potentially resulting in an oversized AC. Therefore, it is advisable to consider using a 0.5-ton unit for the second floor, suitable for an area of 300 square feet.

Consequently, you may end up utilizing one 1-ton unit and one 0.5-ton unit, which would be two distinct AC units. However, factors such as the AC’s placement become crucial in the context of a two-story house. It is advisable to consult a technician to accurately assess the required tonnage for your AC units.

Alternatively, you could opt for a single 1.5-ton unit to cool the entire house. Combining the areas of both floors yields a total of 850 square feet, which aligns closely with the 1.5-ton tonnage suitable for areas up to 900 square feet.

Avoid selecting a 2-ton unit since it covers 1,200 square feet, which is excessive for a total area of 850 square feet.

The example above demonstrates the importance of accurately measuring the area before deciding on an additional AC unit. The tonnage does not have to be an exact match, but it should closely correspond to the area’s dimensions to avoid undersizing or oversizing issues.

Correct Tonnage, Yet High Electric Bill

Although you have learned how to estimate the tonnage requirement, your Armstrong AC might still contribute to a higher-than-usual electric bill. Evaluating the AC’s condition can help identify the problem. Consider the following suggestions to address this issue:

Inspect the Wiring
Faulty wiring between your AC and the main electrical source can lead to increased electricity consumption. Ensure that the wires are of high quality and properly insulated to avoid exposure.

Additionally, check the voltage compatibility of the AC, which can be found in the data sheet. It is crucial to prevent electrical overload and incompatibility, as they can result in higher utility bills.

Check the Refrigerant Level
A low refrigerant level can also cause a significant increase in your electricity bill. When the cooling capacity diminishes, the AC is forced to run longer cycles until the motors become unable to function. Therefore, ensure that your AC has an adequate refrigerant level to maintain optimal performance.

Armstrong Air Conditioner Tonnage: Why It Is Necessary And How To Determine Your AC's Capacity

Fix the Thermostat
A malfunctioning thermostat can display inaccurate temperature readings, leading you to believe that the desired room temperature has not been achieved. Consequently, you may extend the AC’s operation, leading to higher energy consumption.

To address this issue, repair the thermostat and ensure that the batteries are functioning properly. Additionally, keep the thermostat away from damp areas. If necessary, consider replacing the thermostat altogether.


In this article, we have explored various aspects related to determining the tonnage of an Armstrong air conditioner. We have provided relevant examples to help you accurately calculate the required tonnage.

Furthermore, we have emphasized the significance of tonnage in terms of energy efficiency, the condition of your AC, and health considerations. We have also provided guidance on determining the number of AC units needed for your home, using a practical example.

Lastly, we have briefly discussed the possible reasons behind a higher-than-usual electric bill despite having the correct tonnage. Remember to regularly monitor and maintain your AC to ensure optimal performance and energy efficiency.

Armstrong Air Conditioner Tonnage: Why It Is Necessary And How To Determine Your AC's Capacity

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