HVAC VAV System Fundamentals

Measures heat content of return and outside air to determine economizing.

Using outside air for cooling when its heat content is lower than indoor air.

Process of supplying fresh air to occupied spaces for breathing.

Increases CO₂ leading to cognitive decline and health issues.

Balanced systems that recover sensible heat using two blowers.

Recover both sensible and latent heat using a desiccant heat wheel.

Minimum position for economizing units is typically 10%.

Thermometers, psychrometers, and multimeters are used for calibrating system sensors.

The ideal location for a pressure sensor is as far from the blower as possible to accurately measure duct pressure.

Zoning is used to manage temperature differences in various home areas by controlling airflow with dampers and thermostats.

Significant temperature differences can exist between floors; for example, a 10°F difference is common between levels.

A zone damper regulates airflow in a branch line based on conditions sensed by a thermostat in the zone.

A terminal reheat system provides cooled air and fine-tunes zone temperatures using reheat coils at terminal units.

The central air handler supplies cool, dehumidified air to all the zones in a terminal reheat system.

An induction reheat system mixes primary air with room air and reheats it before supplying it to the space.

Heating coils in terminal units warm the air when a specific zone requires additional heating.

A device that reduces humidity in air before it enters a building.

An air-conditioning system that circulates a fixed amount of air regardless of demand.

Ventilation that adjusts based on occupancy and CO₂ levels.

These systems adjust air volume based on specific space needs.

Devices in VAV systems that control airflow and temperature in each zone.

A component that warms air before it is circulated back into a space.

A device in a VAV box that regulates airflow based on pressure changes.

Ensures there is adequate air pressure in a duct system.

An air handling unit that supplies high-velocity primary air through ductwork for HVAC systems.

Devices that draw in room air and mix it with primary air using the Venturi effect.

Valves that regulate water flow in heating systems based on thermostat signals.

Valves that control individual heating zones, but can increase supply header pressure if multiple are closed.

Valves that maintain constant water flow, redirecting to the boiler when zones don’t require heat.

Determining moisture load based on building size, climate, occupancy, and ventilation rates.

Measured in pints per day, it's used to determine the moisture removal needed for spaces.

A refrigeration process for comfort cooling, operating as a high-temperature system with temperatures above freezing.

Includes compressor, condenser, metering device, and evaporator.

Uses 100% outdoor air to cool by absorbing moisture as air passes through wet media.

A cooler where a pump lifts water to a pad that the air passes through, absorbing moisture and cooling the air.

A cooler that sprays water onto a pad where air passes through, evaporating moisture to cool the air.

A motor rotates an evaporative pad through a water sump, cooling the air as the pad is wet.

Uses outdoor temperature to determine when to economize cooling based on a fixed setpoint.

Compares return air temperature with outdoor temperature to decide on economizing.

Humidifiers output is rated in gallons per day (GPD) for control.

Recommended humidity level for comfort is 30-50%.

Includes portable, whole-house, and commercial types for varied uses.

Includes portable for rooms and whole-house integrated with HVAC.

Device used to measure humidity levels in the air.

Amount of refrigerant required for proper system operation.

Difference in refrigerant temperature above surrounding air.