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Most commonly, VAV boxes are pressure independent, meaning the VAV box uses controls to deliver a constant flow rate regardless of variations in system pressures experienced at the VAV inlet. [2] This is accomplished by an airflow sensor that is placed at the VAV inlet which opens or closes the damper within the VAV box to adjust the airflow. [2]
Such a control sequence is supported by a pollutant sensor (e.g. carbon dioxide sensor), a variable frequency drive (VFD) on the fan supplying the zone, individual VAV boxes with reheat serving each space in the zone, and airflow measuring stations. [4] Research has been conducted on the application of DCV in constant-air-volume (CAV) systems.
In variable-flow hydronic systems, reducing pump speed or staging of pumps with boilers and chillers to suit part-load conditions is an energy efficient method of control. [5] VAV (variable air flow) systems meet the needs of large modern commercial-use buildings, with internal spaces divided into open-plan areas.
Air flow control (CAV or VAV air handlers) Zone control (single zone or multi zone air handlers) Fan location (draw-through or blow-through) Direction of outlet air flow (front, up, or down) Package model (horizontal or vertical) But, the first method is very usual in HVAC market. In fact, most of the company advertise their products by air ...
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. However, variations such as CAV with reheat, CAV multizone, and CAV primary-secondary systems can serve multiple zones and larger buildings.
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.
A damper is a valve or plate that stops or regulates the flow of air inside a duct, chimney, VAV box, air handler, or other air-handling equipment. A damper may be used to cut off central air conditioning (heating or cooling) to an unused room, or to regulate it for room-by-room temperature and climate control - for example, in the case of ...
The flow is proportional to the absolute inlet pressure, so the flow in scfm would equal the C v flow coefficient if the inlet pressure were reduced to 2 psia and the outlet were connected to a vacuum with less than 1 psi absolute pressure (1.0 scfm when C v = 1.0, 2 psia input).