If a pitot tube connected to an inclined manometer reads 0.2" water column, what is the calculated air velocity?

To determine the air velocity based on the reading from a pitot tube, you can use the formula that relates the differential pressure measured by the pitot tube to the velocity of the air. The formula is derived from Bernoulli's principle and is given by:

[ V = 4005 \sqrt{h} ]

where ( V ) is the velocity in feet per minute (FPM) and ( h ) is the pressure difference in inches of water column.

In this case, the pitot tube reads 0.2 inches of water column. Plugging that value into the formula, we get:

[ V = 4005 \sqrt{0.2} ]

First, calculate the square root of 0.2, which is approximately 0.447. Then multiply this by 4005:

[ V = 4005 \times 0.447 ] [ V ≈ 1788.9 ]

This rounds to approximately 1791 FPM, which corresponds to the correct answer. Understanding this calculation and the relationship between pressure and air velocity is crucial in HVAC applications, as it allows technicians to assess system performance effectively.