.Buildings.Obsolete.Controls.OBC.ASHRAE.G36_PR1.AHUs.MultiZone.VAV.SetPoints.SupplyTemperature .Buildings.Obsolete.Controls.OBC.ASHRAE.G36_PR1.AHUs.MultiZone.VAV.SetPoints.SupplyTemperatureBlock that outputs the supply air temperature setpoint and the coil valve control inputs for VAV system with multiple zones, implemented according to the ASHRAE Guideline G36, PART 5.N.2 (Supply air temperature control).
The control loop is enabled when the supply air fan uSupFan is proven on,
and disabled and the output set to Deadband otherwise.
The supply air temperature setpoint is computed as follows.
TSupSetMin, TSupSetMax,
TSupSetDes, TOutMin, TOutMax
The default range of outdoor air temperature (TOutMin=16°C,
TOutMax=21°C) used to reset the occupied mode TSupSet
was chosen to maximize economizer hours. It may be preferable to use a lower
range of outdoor air temperature (e.g. TOutMin=13°C,
TOutMax=18°C) to minimize fan energy.
The TSupSetMin variable is used during warm weather when little reheat
is expected to minimize fan energy. It should not be set too low or it may cause
excessive chilled water temperature reset requests which will reduce chiller
plant efficiency. It should be set no lower than the design coil leaving air
temperature.
The TSupSetMax variable is typically 18 °C in mild and dry climate,
16 °C or lower in humid climates. It should not typically be greater than
18 °C since this may lead to excessive fan energy that can offset the mechanical
cooling savings from economizer operation.
uOpeMod=1)
The TSupSet shall be reset from TSupSetMin when the outdoor
air temperature is TOutMax and above, proportionally up to
maximum supply temperature when the outdoor air temperature is TOutMin and
below. The maximum supply temperature shall be reset using trim and respond logic between
TSupSetDes and TSupSetMax. Parameters suggested for the
trim and respond logic are shown in the table below. They require adjustment
during the commissioning and tuning phase.
| Variable | Value | Definition |
|---|---|---|
| Device | AHU Supply Fan | Associated device |
| SP0 | iniSet | Initial setpoint |
| SPmin | TSupSetDes | Minimum setpoint |
| SPmax | TSupSetMax | Maximum setpoint |
| Td | delTim | Delay timer |
| T | samplePeriod | Time step |
| I | numIgnReq | Number of ignored requests |
| R | uZonTemResReq | Number of requests |
| SPtrim | triAmo | Trim amount |
| SPres | resAmo | Respond amount |
| SPres_max | maxRes | Maximum response per time interval |
uOpeMod=2, uOpeMod=3)
Supply air temperature setpoint TSupSet shall be TSupSetMin.
uOpeMod=4, uOpeMod=5)
Supply air temperature setpoint TSupSet shall be TSupWarUpSetBac.
Supply air temperature shall be controlled to setpoint using a control loop whose output is mapped to sequence the hot water valve or modulating electric heating coil (if applicable) or chilled water valves.