blockController
Single zone VAV AHU economizer control sequence
Information
Single zone VAV AHU economizer control sequence that calculates outdoor and return air damper positions based on ASHRAE Guidline 36, PART 5 sections: P.4.d, P.5, P.9, P.3.b, A.17.
The sequence consists of three subsequences.
-
First, the block
damLimcomputes the damper position limits to satisfy outdoor air requirements. See Buildings.Obsolete.Controls.OBC.ASHRAE.G36_PR1.AHUs.SingleZone.VAV.Economizers.Subsequences.Limits for a description. -
Second, the block
enaDisenables or disables the economizer based on outdoor temperature and optionally enthalpy, and based on the supply fan status, freeze protection stage and zone state. See Buildings.Obsolete.Controls.OBC.ASHRAE.G36_PR1.AHUs.SingleZone.VAV.Economizers.Subsequences.Enable for a description. -
Third, the block
modmodulates the outdoor and return damper position to track the supply air temperature setpoint for heating, subject to the limits of the damper positions that were computed in the above two blocks. See Buildings.Obsolete.Controls.OBC.ASHRAE.G36_PR1.AHUs.SingleZone.VAV.Economizers.Subsequences.Modulation for a description.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Boolean | use_enthalpy | false | Set to true if enthalpy measurement is used in addition to temperature measurement |
| Boolean | use_fixed_plus_differential_drybulb | false | Set to true to only evaluate fixed plus differential dry bulb temperature high limit cutoff; shall not be used with enthalpy |
| Boolean | use_TMix | true | Set to true if mixed air temperature measurement is enabled |
| Boolean | use_G36FrePro | false | Set to true if G36 freeze protection is implemented |
| Real | uMin | 0.1 | Lower limit of controller output at which the dampers are at their limits |
| Real | uMax | 0.9 | Upper limit of controller output at which the dampers are at their limits |
| Advanced › Hysteresis | |||
| Real | delTOutHis | 1 | Delta between the temperature hysteresis high and low limit |
| Real | delEntHis | 1000 | Delta between the enthalpy hysteresis high and low limits |
| Modulation | |||
| Buildings.Controls.OBC.CDL.Types.SimpleController | controllerTypeMod | Buildings.Controls.OBC.CDL.Types.SimpleController.PI | Type of controller |
| Real | kMod | 1 | Gain of modulation controller |
| Real | TiMod | 300 | Time constant of modulation controller integrator block |
| Real | TdMod | 0.1 | Time constant of derivative block for modulation controller |
| Freeze protection | |||
| Buildings.Controls.OBC.CDL.Types.SimpleController | controllerTypeFre | Buildings.Controls.OBC.CDL.Types.SimpleController.PI | Type of controller |
| Real | kFre | 0.1 | Gain for mixed air temperature tracking for freeze protection, used if use_TMix=true |
| Real | TiFre | 120 | Time constant of controller for mixed air temperature tracking for freeze protection. Require TiFre < TiMinOut |
| Real | TdFre | 0.1 | Time constant of derivative block for freeze protection |
| Real | TFreSet | 277.15 | Lower limit for mixed air temperature for freeze protection, used if use_TMix=true |
| Commissioning › Damper position limits | |||
| Real | yFanMin | 0.1 | Minimum supply fan operation speed |
| Real | yFanMax | 0.9 | Maximum supply fan operation speed |
| Real | VOutMin_flow | 1.0 | Calculated minimum outdoor airflow rate |
| Real | VOutDes_flow | 2.0 | Calculated design outdoor airflow rate |
| Real | yDam_VOutMin_minSpe | 0.4 | Outdoor air damper position to supply minimum outdoor airflow at minimum fan speed |
| Real | yDam_VOutMin_maxSpe | 0.3 | Outdoor air damper position to supply minimum outdoor airflow at maximum fan speed |
| Real | yDam_VOutDes_minSpe | 0.9 | Outdoor air damper position to supply design outdoor airflow at minimum fan speed |
| Real | yDam_VOutDes_maxSpe | 0.8 | Outdoor air damper position to supply design outdoor airflow at maximum fan speed |
| Commissioning › Physical damper position limits | |||
| Real | outDamPhyPosMax | 1 | Physically fixed maximum position of the outdoor air damper |
| Real | outDamPhyPosMin | 0 | Physically fixed minimum position of the outdoor air damper |
| Real | retDamPhyPosMax | 1 | Physically fixed maximum position of the return air damper |
| Real | retDamPhyPosMin | 0 | Physically fixed minimum position of the return air damper |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | THeaSupSet | Supply air temperature heating setpoint | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | TSup | Measured supply air temperature | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | TOut | Outdoor air temperature | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | TCut | Outdoor air temperature high limit cutoff. For differential dry bulb temeprature condition use return air temperature measurement | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | TRet | Used only for fixed plus differential dry bulb temperature high limit cutoff | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | hOut | Outdoor air enthalpy | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | hCut | Outdoor air enthalpy high limit cutoff. For differential enthalpy use return air enthalpy measurement | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | TMix | Measured mixed air temperature, used for freeze protection | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | VOutMinSet_flow | Minimum outdoor airflow setpoint | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | uSupFanSpe | Supply fan speed | |
| Buildings.Controls.OBC.CDL.Interfaces.IntegerInput | uZonSta | Zone state signal | |
| Buildings.Controls.OBC.CDL.Interfaces.IntegerInput | uFreProSta | Freeze protection status | |
| Buildings.Controls.OBC.CDL.Interfaces.IntegerInput | uOpeMod | AHU operation mode status signal | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanInput | uSupFan | Supply fan status | |
| Buildings.Controls.OBC.CDL.Interfaces.RealOutput | yRetDamPos | Return air damper position | |
| Buildings.Controls.OBC.CDL.Interfaces.RealOutput | yOutDamPos | Outdoor air damper position | |
| Buildings.Controls.OBC.CDL.Interfaces.RealOutput | yHeaCoi | Heating coil control signal |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Buildings.Obsolete.Controls.OBC.ASHRAE.G36_PR1.AHUs.SingleZone.VAV.Economizers.Subsequences.Enable | enaDis | Single zone VAV AHU economizer enable/disable sequence | |
| Buildings.Obsolete.Controls.OBC.ASHRAE.G36_PR1.AHUs.SingleZone.VAV.Economizers.Subsequences.Limits | damLim | Single zone VAV AHU economizer minimum outdoor air requirement damper limit sequence | |
| Buildings.Obsolete.Controls.OBC.ASHRAE.G36_PR1.AHUs.SingleZone.VAV.Economizers.Subsequences.Modulation | mod | Single zone VAV AHU economizer damper modulation sequence | |
| Buildings.Obsolete.Controls.OBC.ASHRAE.G36_PR1.Generic.FreezeProtectionMixedAir | freProTMix | Block that tracks TMix against a freeze protection setpoint |
Revisions
-
July 30, 2019, by Kun Zhang:
Added fixed plus differential dry bulb temperature high limit cut off. -
October 31, 2018, by David Blum:
Added heating coil output. -
June 28, 2017, by Milica Grahovac:
First implementation.