What is difference between VAV and CAV?

Variable air volume (VAV) is a type of heating, ventilating, and/or air-conditioning (HVAC) system. Unlike constant air volume (CAV) systems, which supply a constant airflow at a variable temperature, VAV systems vary the airflow at a constant temperature.

Where are dual ducts used?

In Double Duct system, two separate ducts are run from the central unit to each of the air terminals, as shown in figure below. In winter two warm air streams, of different temperatures, are carried to the air terminals, for individual mixing.

What is the purpose of dual duct system in air conditioning?

Single Fan, Dual Duct – A single-fan, dual-duct system uses a single fan to supply air through two primary air ducts, supplying cool air and warm air. Air from each of these ducts is then mixed in a terminal unit (VAV mixing box or CV mixing box) and supplied to the zone as a single air stream.

What is dual duct VAV?

Dual-duct terminal units are used in a special type of air distribution system where the main system has both warm air and cold air separately ducted to each terminal unit. The flow of both warm air and cool air is modulated, delivering air to the VAV zone at variable air volumes as well as variable temperatures.

What is a dual duct system?

In the dual-duct system, warm air and cool air travel through separate ducts and are mixed to reach a desired temperature. A simpler way to control temperature is to regulate the amount of cold air supplied, cutting it off once a desired temperature is reached.

What is a CAV box in HVAC?

Constant air volume (CAV) is a type of heating, ventilating, and air-conditioning (HVAC) 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. Most CAV systems are small, and serve a single thermal zone.

What is dual duct system?

Dual Fan, Dual Duct – A dual-fan, dual-duct system uses two fans to supply air through two primary air ducts, supplying cool air and warm air. One fan serves the warm air duct, and the other serves the cool air duct.

What is a CAV box?

A CAV unit operates the fan and compressor at full capacity until the temperature drops to a specified setting, then the compressor turns off. The on/off cycling is not efficient at keeping the space at a constant temperature. CAV systems are small and serve a single thermal zone.

How does a CAV work?

What is the difference between a single duct and a dual-duct system?

Dual-duct systems have either one or two supply fans and two duct systems. One duct system carries heated air and the other duct system carries cooled air. Heated air and cooled air are modulated and/or mixed at each zone in the proper proportions to control zone temperature.

What is variable air volume system & dual duct system?

Dual duct variable air volume (DDVAV)) systems are used to obtain zone temperature control by mixing the cold and warm air in various volume combinations. The fan is sized for the anticipated maximum coincident hot or cold volume, not the sum of the instantaneous peaks.

Are VRF systems constant volume?

This template generates a central DOAS air handling unit that provides a constant volume of conditioned outside air to all zones.

What is a constant volume box?

Constant air volume systems are consistently used on medium to large projects to supply regulated fresh-air requirements to each zone/floor as well as extracting ‘used’ air from the building.

Where is CAV system used?

There are two types of CAV systems that are commonly in use to modify the supply air temperature: the terminal reheat system and the mixed air system. The terminal reheat system cools the air in the air handling unit down to the lowest possible needed temperature within its zone of spaces.