Question

You are checking for proper airflow in CFM on a three ton heat pump system. The system has one return grill measuring 24" x 24", which has a net free area of 3.4 square feet. You measure air velocity and calculate an average of 400 FPM. From this information you can conclude that _________.

1) The CFM of the system is 1360
2) The CFM of the system is 1700
3) The CFM of the system is 2040
4) The CFM of the system cannot be determined from the given information

Answer 1

The CFM of the system is calculated using the formula CFM = Area × Velocity. With an area of 3.4 square feet and an air velocity of 400 FPM, the CFM is found to be 1360. Therefore, option 1 is correct.

Step-by-step explanation:

To calculate the CFM of the system, we need to use the area of the return grill and the measured air velocity. The area in square feet is 24 inches by 24 inches, which equals 2 feet by 2 feet. This gives an area of 4 square feet. However, we are provided with a net free area, which is 3.4 square feet. The average air velocity is 400 FPM (feet per minute).

The formula to calculate CFM (Cubic Feet per Minute) is:

CFM = Area (in square feet) × Velocity (in FPM)

By inputting the values we have:

CFM = 3.4 sq ft × 400 FPM = 1360 CFM

Therefore, option 1 is the correct answer; the CFM of the system is 1360.