Manual Air Conditioning Load Calculator

Air Conditioning Load Equation:

\[ BTU/h = U \times A \times \Delta T + Solar + Occupants \]

U-value (U):

BTU/h-ft²-°F

Area (A):

square feet

Temperature Difference (ΔT):

°F

Solar Gain:

BTU/h

Occupant Heat:

BTU/h

Total Cooling Load:

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1. What is the Air Conditioning Load Calculation?

The air conditioning load calculation estimates the amount of cooling required to maintain comfortable conditions in a space. It accounts for heat transfer through building materials (U-value), solar heat gain, and heat generated by occupants.

2. How Does the Calculator Work?

The calculator uses the basic cooling load equation:

\[ BTU/h = U \times A \times \Delta T + Solar + Occupants \]

Where:

\( U \) — U-value of the building material (BTU/h-ft²-°F)
\( A \) — Area of the surface (square feet)
\( \Delta T \) — Temperature difference between inside and outside (°F)
\( Solar \) — Solar heat gain through windows (BTU/h)
\( Occupants \) — Heat generated by people in the space (BTU/h)

Explanation: The equation calculates the total heat that must be removed by the air conditioning system to maintain the desired indoor temperature.

3. Importance of Cooling Load Calculation

Details: Proper load calculation is essential for sizing HVAC equipment correctly. Oversized units short-cycle, reducing efficiency and comfort, while undersized units can't maintain temperature.

4. Using the Calculator

Tips: Enter accurate U-values for your building materials, total area, expected temperature difference, and account for solar gain and occupants. For more precise calculations, consider professional Manual J calculations.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical U-value for walls?
A: Modern insulated walls typically have U-values between 0.05-0.25 BTU/h-ft²-°F, while older uninsulated walls may be 0.5 or higher.

Q2: How much heat do occupants generate?
A: Approximately 250-400 BTU/h per person depending on activity level (more for exercise, less for sedentary activities).

Q3: What about other heat sources?
A: This simplified calculator doesn't account for appliances, lighting, or ventilation. A complete load calculation would include these factors.

Q4: How does solar gain vary?
A: Solar gain depends on window size, orientation, shading, and time of day. South-facing windows in summer can add 100-250 BTU/h per square foot.

Q5: What's the next step after calculating BTU/h?
A: HVAC professionals typically divide the total BTU/h by 12,000 to determine required tons of cooling capacity (1 ton = 12,000 BTU/h).