What is a dual duct terminal unit?
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 an HVAC terminal unit?
A terminal unit is a device that is used to regulate the volume of conditioned primary air from the central air handler to the occupied space.
How does a dual duct system work?
A dual duct system has two separate supply ducts from the HVAC unit to the outlets in the spaces. One duct supplies cold air, and the other supplies heated air. In this system both the heating and cooling coils operate at the same time, just as with the multizone system.
What is a single duct VAV?
The simplest and most common system—single-duct VAV—comprises a central VAV air handler and several local VAV boxes, one for each space or thermal control zone. See Figure 1. The air handler delivers primary air (a mixture of first-pass outdoor and recirculated return air) to the VAV boxes through a single duct.
What is the advantage of a dual duct system?
The advantages include: Good temperature and humidity control. Accommodates a variety of zone loads. Ease of adding or subdividing zones in the future. Adaptable to either constant volume or VAV systems.
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 difference between VAV & 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.
What is the difference between CAV and VAV?
While a CAV system uses variable air temperature and constant airflow, a VAV system keeps constant temperature and variable airflow.
Why are dual duct systems no longer used?
They are no longer popular due to their high energy consumption, although they are sometimes used in hospitals where VAV is inappropriate.
What is the difference between VAV and VRV?
VAV is the method/device used to control the air quantity so as to attain the desired temperature in different rooms. VRV and VRF are both same and are tpy of cooling system and having the beauty of cooling and heating the different spaces of a building with the same system.
What does CAV mean in HVAC?
constant air volume
Twenty to thirty years ago it was common practice to install a CAV (constant air volume) system in commercial buildings for ventilation and air-conditioning. These types of HVAC systems require high airflow rates and higher amounts of energy for heating and cooling.
Is a VAV an AHU?
VAV systems supply air at a variable temperature and airflow rate from an air handling unit (AHU). Because VAV systems can meet varying heating and cooling needs of different building zones, these systems are found in many commercial buildings.
Is AHU and FCU the same?
In simple terms, an air handling unit (AHU) is a component of an HVAC system that cools and distributes air into the space through a duct. A fan coil unit (FCU) is a standalone system that circulates the existing air in a small space, but it can also be a part of an HVAC system.