Question 224General Subjects - 1st Asst/Chief

The correct answer is B) 27%. To arrive at this answer, we need to understand how the psychrometric chart works. When air passes over a heating coil, its dry-bulb temperature increases, but its moisture content (and therefore its relative humidity) decreases. By tracing the 60°F, 52% RH point on the psychrometric chart to the 80°F point, we can see that the relative humidity at the off-coil temperature is 27%. The other options are incorrect because: A) 19% is too low for the given conditions. C) 55% is too high, as the relative humidity decreases when the air is heated. D) 70% is also too high for the given conditions.