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Heating, Venilation & Air Conditioning

Variable Air Volume

Variable Air Volume (VAV) systems are so varied and some are so complex that one set of balancing specifications cannot be written to cover all situations. We consider all situations and have experienced most of them at some point over our 20 year history.

There are three types of VAV boxes: traditional, fan-powered and VAV with reheat. The traditional VAV box consists of VAV box with an integral damper and is controlled by thermostat. This is the most basic type of VAV box. The fan-powered VAV is built the same as the traditional, but it also contains a fan which is triggered when the area reaches optimal temperature or the damper is 50% closed. It provides additional air circulation when there is less demand for conditioned air. A VAV with reheat also is built the same as the traditional VAV, but it contains an electric coil designed to reheat the air when the damper reaches a predetermined position. This feature allows heating in the specific zone instead of having to heat the whole building. A Variable Air Volume (VAV) box, is a part of an air conditioning system. It is located inside the duct work. It is designed to control the air flow to a specific area, called a zone. The VAV regulates the volume of the air to the zone by opening or closing the damper, thus controlling the amount of conditioned air directed to the zone. Each zone in a building has a thermostat which controls the VAV, telling it when to open or shut the damper based upon the needs of the zone.

Variable Air Volume (VAV) systems enable retailers to improve the indoor air quality and customer comfort of their environment, while potentially lowering energy costs. To accomplish this, each Single-Duct VAV Controller communicates with the VAV RTU Controller, enabling the HVAC unit to produce the right temperature and volume of air required at any given time. Since the HVAC unit is rarely operating at full speed, as it would always be doing in a traditional constant volume system, energy is saved. Each Single-Duct VAV Controller can regulate the amount of air, as well as reheat air if required, ensuring each zone is at a comfortable temperature.

In VAV systems, the supply-air quantity varies with load, but the minimum required outside-air quantity does not change. Exhausts, such as toilet exhausts, might be constant regardless of load. Design occupancy and the resulting outside-air quantity required for ventilation also might be constant. If the minimum required outside-air quantity remains constant, but the supply-air quantity decreases, the minimum required outside-air quantity increases as a percentage of the supply-air quantity. When a system operates with minimum outside air (and an economizer is not active), a fixed minimum-outside-air damper position will result in smaller amounts of outside air as the VAV supply-air quantity decreases. While there are many different HVAC system designs and operational approaches to achieving proper system functionality, and every building is unique in its design and operation, HVAC systems generally share a few basic design elements: (1) Outside air intake, (2) Air handling unit a system of fans, heating and cooling coils, air-flow control dampers, air filters, etc., (3) Air distribution system, and (4) an Air exhaust system.