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Load Calculation

Proper sizing of an air conditioning unit is essential to ensure optimal performance, efficiency, and longevity of the system. Here are some steps to guide you through the process of sizing an AC unit.

 

Calculate the area of the room:

The first step is to measure the length and width of the room in feet, and multiply the two values to get the square footage. For example, a room that is 12 feet long and 10 feet wide has an area of 120 square feet.

 

Determine the cooling capacity needed:

The next step is to determine the cooling capacity needed to cool the room effectively. This is measured in British Thermal Units (BTUs) per hour. The general rule of thumb is to use between 15 and 20 BTUs per square foot of the room. For example, a room of 120 square feet would require a cooling capacity of 1800 to 2400 BTUs.


 

  • 500-700 sqft, BTUs ranges from 7,500 to 14,000 BTUs

  • 700-1000 sqft, BTUs ranges from 10,500 to 20,000 BTUs

  • 1000-1300 sqft, BTUs ranges from 15,000 to 26,000 BTUs

  • 1300-1600 sqft, BTUs ranges from 19,500 to 32,000 BTUs

 

Cooling Capacity (BTUs/hour) = Room Size (square feet) x Desired Range of BTUs per square foot

 

Where the Desired Range of BTUs per square foot can be between 15 and 20. For example, if a room is 1000 square feet, and the desired range of BTUs per square foot is 15 to 20, the recommended cooling capacity range would be:

Minimum Cooling Capacity = 1000 sq. ft. x 15 BTUs/sq. ft. = 15 000 BTUs/hour

Maximum Cooling Capacity = 1000 sq. ft. x 20 BTUs/sq. ft. = 20 000 BTUs/hour

 

So in this case, you can choose an AC unit with a cooling capacity between 15 000 and 20 000 BTUs per hour. Other factors may affect the cooling needs of the room. Also, keep in mind that this is a general formula, and it's always best to consult with a professional to ensure the proper sizing of the AC unit for their specific needs.

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Determine the Heating Capacity Needed:

The next step is to determine the heating capacity required to keep the room warm effectively. This capacity is measured in British Thermal Units (BTUs) per hour. The general rule of thumb for heating is to use between 30 and 35 BTUs per square foot of the room. For example, a room of 120 square feet would require a heating capacity of 3600 to 4200 BTUs.

  • 500-700 sqft, the required BTUs for heating ranges from 15,000 to 24,500 BTUs.

  • 700-1000 sqft, the required BTUs for heating ranges from 21,000 to 35,000 BTUs.

  • 1000-1300 sqft, the required BTUs for heating ranges from 30,000 to 45,500 BTUs.

  • 1300-1600 sqft, the required BTUs for heating ranges from 39,000 to 56,000 BTUs.

Heating Capacity (BTUs/hour) = Room Size (square feet) x Desired Range of BTUs per square foot

Where the Desired Range of BTUs per square foot can be between 30 and 35. For example, if a room is 1000 square feet, and the desired range of BTUs per square foot is 30 to 35, the recommended heating capacity range would be:

  • Minimum Heating Capacity = 1000 sq. ft. x 30 BTUs/sq. ft. = 30,000 BTUs/hour

  • Maximum Heating Capacity = 1000 sq. ft. x 35 BTUs/sq. ft. = 35,000 BTUs/hour

In this scenario, you should choose a heating system with a capacity between 30,000 and 35,000 BTUs per hour. It's important to consider other factors that may affect the heating needs of the room, such as insulation quality, window sizes, and exposure to sunlight. This formula provides a basic guideline, and consulting with a heating professional is recommended to ensure the proper sizing of the heating system for your specific needs.

Consider other factors:
Other factors that can impact the cooling and heating capacity needed include the climate of the area, the level of insulation in the room, the number of windows, and the number of people who will be using the room.Choose the right AC unit: Once the cooling and heating capacity needed has been determined, you can choose an AC or heatpump unit that meets that need.

It's important to note that selecting a unit that is too small will result in inadequate cooling or heating, while selecting a unit that is too large will result in unnecessary energy costs and high humidity.

Consult a professional:
If you are unsure about the proper sizing of your AC unit, you should book a consultation with a Klimtech. We can provide guidance and perform a proper load calculation for your home.​​Email us below any capacity questions you might have or to book a load calculation of your home.

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