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VAVs
Overview
The vav
tag is used to model variable air volume terminal units. VAVs are supplied conditioned air from an AHU and use a damper to modulate the air flow to the zone. Typically VAVs are supplied cool air at a temperature of around 55°F (13°C). Some VAVs support reheat that allow them to heat this cool air to a warmer temperature.
A VAV without reheat must be defined with the coolingOnly
tag. Otherwise, it must define one of the heating process tags. Some reheat VAVs contain a fan, in which case they should also define the fanPowered
tag.
VAVs should define the airRef
tag to reference their supply AHU. When there are multiple supply AHUs, then the airRef
tag should be a list of all the upstream AHUs.
Choices
AHUs define a suite of choices that should be made on a per instance basis.
Heating Process
If the VAV provides reheat, then it should add one of the following heatingProcess
choices:
Or if the VAV does not support reheat, then add the coolingOnly
tag.
When applicable the heating choice marker should also be paired with the appropriate flow ref tag. For example, if a VAV uses hot water for reheat, then it should also define the hotWaterRef
tag to refer to its hot water plant.
Modulation
One of the following vavModulation
markers should be defined:
vavAirCircuitType
If the VAV is fan powered, then one of the following vavAirCircuit
markers should be defined:
Ductwork
One of the following ductConfig
markers should be defined:
Sections
We associate points with sections of a VAV using these tags:
inlet
: air entering the unit from the AHUdischarge
: air exiting the unit to be supplied to the zoneszone
: conditioned space associated with the unit
Since most points are not clearly associated with the inlet or discharge ducts, we typically omit a section tag for most points. However, any points that would conflict with the zone points must be qualified with either inlet
or discharge
.
Examples
The following are examples of fully tagged VAVs:
// Cooling only VAV id: @vav dis: "VAV-Example" vav equip coolingOnly pressureDependent singleDuct airRef: @ahu siteRef: @site // Fan powered VAV with hot water reheat id: @vav vav equip fanPowered hotWaterHeating pressureDependent singleDuct hotWaterRef: @hot-water-plant airRef: @ahu siteRef: @site