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Control of the system's fan capacity is critical in VAV systems. Without proper and rapid flow rate control, the system's ductwork, or its sealing, can easily be damaged by overpressurization. In the cooling mode of operation, as the temperature in the space is satisfied, a VAV box closes to limit the flow of cool air into the space.
Constant air volume (CAV) is a type of heating, ventilating, and air-conditioning system. In a simple CAV system, the supply air flow rate is constant, but the supply air temperature is varied to meet the thermal loads of a space. [1] Most CAV systems are small, and serve a single thermal zone.
DCV is primarily used in variable-air-volume (VAV) systems. In DCV VAV systems, airflow to a zone is modulated to control the temperature and outdoor airflow to the space. Using the pollutant levels measured in a zone, the system’s controller sets the zone’s minimum airflow requirement to dilute the pollutant concentration. [4]
A zone damper (also known as a Volume Control Damper or VCD) is a specific type of damper used to control the flow of air in an HVAC heating or cooling system. In order to improve efficiency and occupant comfort, HVAC systems are commonly divided up into multiple zones.
The total outdoor air intake of the ventilation system (in multiple-zone variable air volume (VAV) systems) might therefore be similar to the airflow required by the 1989 standard. From 1999 to 2010, there was considerable development of the application protocol for ventilation rates.
Diagramatic operation of a thermal wheel Ljungström Air Preheater by Swedish engineer Fredrik Ljungström (1875–1964). A thermal wheel, also known as a rotary heat exchanger, or rotary air-to-air enthalpy wheel, energy recovery wheel, or heat recovery wheel, is a type of energy recovery heat exchanger positioned within the supply and exhaust air streams of air-handling units or rooftop ...
Most new commercial buildings have VAV systems. VAVs may be bypass type or pressure dependent. Pressure dependent type VAVs save energy while both types help in maintaining temperature of the zone that it feeds. Abbreviated VAV. zoning system A zoning system sections a building or a space into zones which are controlled independently of each other.
4 – Heating and/or cooling coil 5 – Filter compartment 6 – Mixed (recirculated + outside) air duct A rooftop packaged unit or RTU. An air handler, or air handling unit (often abbreviated to AHU), is a device used to regulate and circulate air as part of a heating, ventilating, and air-conditioning system. [1]