HVAC tab in model data - Compact HVAC
VAV (variable air volume) and CAV (constant volume) system types are both based on the EnergyPlus VAV system type and so have similar common data entry.
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.
Only one VAV system can be defined per building.
Note: the Compact HVAC type must be set to VAV at building level and in all zones which are part of the VAV system. Other zones can have HVAC type Unitary single zone or Fan coil units but not Unitary multizone or CAV.
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 .
Only one CAV system can be defined per building.
Note: the Compact HVAC type must be set to CAV at building level and in all zones which are part of the CAV system. Other zones can have HVAC type Unitary single zone or Fan coil units but not Unitary multizone or VAV.
When using Compact HVAC data, the HVAC Type is displayed beneath the Template. This cannot be edited directly - if you want to choose a different HVAC system type you should do this by selecting an appropriate template.
When using Compact HVAC data, the system availability schedule can be defined to control the overall operation of the HVAC system, including heating, cooling and ventilation. This schedule is used at the building level for VAV and CAV systems.
The rest of this section covers both VAV and CAV with differences pointed out where appropriate.
You can also open headers to enter HVAC details where they are different from those loaded from the template: