Latent Moisture
Dehumidification Matrix
Audit air volume circulation rates against absolute humidity drops to calculate total pint-per-day condensate extraction mass.
Psychrometric Air Balancing & The Mechanics of Latent Vapor Removal Overview
Total air conditioning capacity is split into two distinct thermodynamic categories: sensible cooling (dropping the temperature you read on a standard thermometer) and latent cooling (extracting the physical weight of water vapor suspended in the air mass). Absolute humidity is calculated using grains of water per pound of dry air ($7,000 \text{ grains} = 1 \text{ pound of pure water}$). When warm, humid air hits an indoor evaporator coil running below the dew point temperature, the gaseous water vapor changes its state into liquid condensate. The volume of moisture extracted depends on the air volume velocity (CFM) and the weight drop in grains across the coil plane. In regions with persistent high humidity, systems must be calibrated to run a colder coil with prolonged contact periods to maximize latent moisture extraction before satisfying sensible thermostat setpoints.
Frequently Asked Questions
A: Increasing airflow velocity (CFM) raises the temperature of the evaporator coil surface and shortens the time the air spends in contact with the fins (“dwell time”). Because the air moves too quickly, its moisture content cannot cool past the dew point boundary layer. This converts the system’s focus into almost entirely sensible cooling, lowering the room temperature quickly while leaving the absolute humidity high, resulting in a cold but sticky and uncomfortable indoor climate.
A: Standard systems turn off once the targeted room temperature is met, allowing humidity to creep back up during long off-periods. Systems equipped with hot-gas reheat use an auxiliary coil located downstream of the evaporator. When humidity spikes, the system continues running to extract water vapor, then routes hot refrigerant discharge gas into the reheat coil to warm the chilled air back up to room temperature before it leaves the air handler, keeping spaces perfectly dry without over-cooling.