Why are we using VAV & CAV Boxes in HVAC system and where to use vav and where to use CAV Box?

VAV is used where the conditioning space  ( Office , Residential Rooms, etc ) load varies . It's control box is interfaced with the thermostat and works with respect to the set temperature.Once the temperature has been achieved it turns to allow the minimum air flow to the space and thus creating a difference in static pressure in the duct and send signal to the AHU's VFD to reduce the frequency and thus saves the energy consumption. It's applicable for both variable and constant flow chilled water system.

CAV is used where constant air flow is requires  ie; gathering  areas such as Lobbies, Entrance halls , Prayer halls .It's applicable for constant flow chilled water system.

The VAV & CAV are used where there is an AHU serving many different rooms, so it will help to easily control the temperature of each room separately through thermostat connected to it.

VAV's are used where you have rooms like offices , bed rooms, ....

CAV's are used where you have Lobbies, halls, ....

VAV's should be connected to AHU whch has a VFD motor (Varuable speed fan).

VAV:-  In VAV's the Flow will be Varied & Temperature remains constant.

CAV:-  In CAV's the Flow remains Content & Temperature will be Varied (in this case we have to use duct heater to vary the temperature).

CAV , VAV are applicable at any building according to designer viewpoints .

CAV usually used for small buildings, and may be combined with constant chilled water flow or variable chilled water, for energy conservation.

VAV usually used for large scale building which has high energy consumption, and it must combined with vaiable speed AHU.

The VAV option allows you to model Variable Air Volume (VAV) HVAC configuration with optional preheat, air handling unit heating and cooling coils and reheat and several different heating coil options. You can select series or parallel fan powered terminal units (also known as powered induction units or PIU). There are options to control the air distribution system in various ways including the ability to ensure minimum fresh air delivery to each zone, set VAV box minimum flow fraction and various outside air options including an economiser to provide free cooling when appropriate and heat recovery. You can also model heating and cooling coil temperature reset.

The CAV option allows you to model Constant Air Volume HVAC configuration with optional preheat, main AHU heating coils and zone terminal reheat and several different heating coil options. There are options to control the air distribution system in various ways including the ability to ensure minimum fresh air delivery to each zone, set various outside air options including an economiser to provide free cooling when appropriate and heating and cooling coil temperature reset .

I want to manufacture CAV and VAV boxes. Can somebody help me in designing of these boxes with drawing, design features etc?

Kemal

 In a CAV box, the supply air flow rate is constant. it is used  for small to mid range buildings.

In a VAVbox,the supply of air is varing at a constant temperature. It is used  for mid to large range buildings.

The VAV is used where AHU, FCU serving many different room like offices and residential . we connect separately thermostat for control the temperature and we install in duct

CAV were we required constant flow we use in duct

V.A.V is variable air volume and it is a constant temperature system..this system will satisfies  the cooling and heating load of a building by varying the supply of air volume to the condition space. vav consists of central having air fan which delivers the air to zone terminal devices. 

C.A.V is constant air volume. it is a variable temperature system..in this system the supply of air volume to

Variable Air Volume units are usually used in offices or in places  where cooling demand varies. Constant Air Volume units are usually used in technical and equipment rooms, or in places where the cooling demand is constant

Variable air volume(VAV) box are the equipment often used in the AC Ducts to regulate the volume of air flow by keeping the temperature constant. Air volume can be adjusted by adjusting the dampers.

Constant Air Volume (CAV) box are the equipment often used in the AC Ducts to keep the air flow rate at constant.