What is the impact of dry bulb reset on supply air?

• A. It reduces humidity to acceptable levels.
• B. It affects the dewpoint of supply air and may increase relative humidity too much.
• C. It has no effect on humidity.
• D. It always lowers supply air temperature without affecting humidity.

Answer: (B)

Dry-bulb reset changes the temperature of the air you supply in response to outdoor conditions. When you lower the supply-air temperature, the air can’t carry as much moisture unless more moisture is removed, so the relative humidity in the space can rise if latent loads aren’t matched. The dew point of the supply air is tied to its moisture content, so resetting the dry-bulb alters the supply air’s dew point in a way that can push space humidity up, especially on humid days. This is why the effect is described as affecting the dew point of the supply air and potentially increasing relative humidity too much.