Which statement correctly describes wet-coil versus dry-coil control?

Which statement correctly describes wet-coil versus dry-coil control?

• A. Wet-coil control accounts for latent heat only; dry-coil control accounts for sensible heat only.
• B. Wet-coil control uses water; dry-coil control uses refrigerant.
• C. Wet-coil control accounts for sensible heat only; dry-coil control accounts for latent heat only.
• D. Wet-coil control accounts for both sensible and latent heat, while dry-coil control accounts for only sensible heat.

Answer: (C)

The concept here is how the coil’s moisture condition affects what the control primarily targets: sensible heat (air temperature) versus latent heat (moisture content). A wet coil is arranged so that the cooling effect mainly lowers the air temperature by transferring heat more effectively, but it is not relied on to remove moisture from the air. In that setup, the control focuses on reducing sensible cooling load—changing the temperature—while humidity changes are not the primary target of this coil. A dry coil, on the other hand, operates in a way that highlights moisture removal. When air is cooled to below its dew point on a dry coil, moisture condenses on the coil surface, which changes the air’s moisture content and thus removes latent heat. The control emphasis shifts to managing that latent change (humidity) rather than just lowering temperature. So, the statement that wet-coil control addresses sensible heat only and dry-coil control addresses latent heat only fits the intended distinction: one coil type is used to drive temperature (sensible) changes, while the other is used to drive moisture (latent) changes. The other options mix up which form of heat each coil type primarily affects.

The concept here is how the coil’s moisture condition affects what the control primarily targets: sensible heat (air temperature) versus latent heat (moisture content). A wet coil is arranged so that the cooling effect mainly lowers the air temperature by transferring heat more effectively, but it is not relied on to remove moisture from the air. In that setup, the control focuses on reducing sensible cooling load—changing the temperature—while humidity changes are not the primary target of this coil.

A dry coil, on the other hand, operates in a way that highlights moisture removal. When air is cooled to below its dew point on a dry coil, moisture condenses on the coil surface, which changes the air’s moisture content and thus removes latent heat. The control emphasis shifts to managing that latent change (humidity) rather than just lowering temperature.

So, the statement that wet-coil control addresses sensible heat only and dry-coil control addresses latent heat only fits the intended distinction: one coil type is used to drive temperature (sensible) changes, while the other is used to drive moisture (latent) changes. The other options mix up which form of heat each coil type primarily affects.