.Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.Controller .Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.ControllerBlock that is applied for multizone VAV AHU control. It outputs the supply fan status and the operation speed, outdoor and return air damper position, supply air temperature setpoint and the valve position of the cooling and heating coils. It is implemented according to the Section 5.16 of ASHRAE Guideline 36, May 2020.
The sequence consists of eight types of subsequences.
The fan speed control is implemented according to Section 5.16.1. It outputs
the boolean signal y1SupFan to turn on or off the supply fan.
In addition, based on the pressure reset request uZonPreResReq
from the VAV zones controller, the
sequence resets the duct pressure setpoint, and uses this setpoint
to modulate the fan speed ySupFanSpe using a PI controller.
See
Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.SetPoints.SupplyFan
for more detailed description.
According to current occupany, supply operation status ySupFan,
zone temperatures and the discharge air temperature, the sequence computes the
minimum outdoor airflow rate setpoint, which is used as input for the economizer control.
More detailed information can be found in
Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.SetPoints.OutdoorAirFlow.
The block outputs outdoor and return air damper position, yOutDamPos and
yRetDamPos. First, it computes the position limits to satisfy the minimum
outdoor airflow requirement. Second, it determines the availability of the economizer based
on the outdoor condition. The dampers are modulated to track the supply air temperature
loop signal, which is calculated from the sequence below, subject to the minimum outdoor airflow
requirement and economizer availability.
See
Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.Economizers.Controller
for more detailed description.
Based on the Section 5.16.2, the sequence first sets the maximum supply air temperature
based on reset requests collected from each zone uZonTemResReq. The
outdoor temperature TOut and operation mode uOpeMod are used
along with the maximum supply air temperature, for computing the supply air temperature
setpoint. See
Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.SetPoints.SupplyTemperature
for more detailed description.
The subsequence retrieves supply air temperature setpoint from previous sequence. Along with the measured supply air temperature and the supply fan status, it generates coil valve positions. See Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.SetPoints.SupplySignals for more detailed description.
Based on the Section 5.16.12, the sequence enables freeze protection if the measured supply air temperature belows certain thresholds. There are three protection stages. See Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.SetPoints.FreezeProtection for more detailed description.
By selecting different building pressure control designs, which includes using actuated relief damper without fan, using actuated relief dampers with relief fan, using return fan with direct building pressure control, or using return fan with airflow tracking control, the sequences controls relief fans, relief dampers and return fans. See belows sequences for more detailed description:
According to the Section 5.16.16, the sequence send out heating or cooling plant requests if the supply air temperature is below or above threshold value, or the heating or cooling valves have been widely open for certain times. See Buildings.Controls.OBC.ASHRAE.G36.AHUs.MultiZone.VAV.SetPoints.PlantRequests for more detailed description.
uCooCoi_actual and uHeaCoi_actual,
added 2-position relief damper position output y1RelDam,
added coil type enumeration so to avoid using flag parameters.0 to 0.0 and 1 to 1.0.uRelFan and uSupFanSpe_actual.