blockController
Cooling tower speed control to maintain condenser water return temperature at setpoint
Information
Block that outputs cooling tower fan speed ySpeSet for maintaining
condenser water return temperature at setpoint. This is implemented
according to ASHRAE Guideline 36-2021, section 5.20.12.2,
item a. It includes four subsequences:
- Reset the tower maximum speed that resets based on the plant partial load ratio linearly from 100% at 50% operative part load ratio down to 70% at 0% load ratio.
- Sequence of enabling and disabling tower fans, see Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Towers.FanSpeed.ReturnWaterTemperature.Subsequences.Enable for a description.
- Sequence of specifying condenser water return temperature setpoint, see Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Towers.FanSpeed.ReturnWaterTemperature.Subsequences.Setpoint for a description.
- Sequence of controlling tower fan for the close coupled plants, see Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Towers.FanSpeed.ReturnWaterTemperature.Subsequences.Coupled for a description.
- Sequence of controlling tower fan for less coupled plants, see Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Towers.FanSpeed.ReturnWaterTemperature.Subsequences.LessCoupled for a description.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Boolean | need_heaPreCon | true | True: the plant requires chiller head pressure being controlled |
| Integer | nChi | 2 | Total number of chillers |
| Integer | nTowCel | 4 | Total number of cooling tower cells |
| Integer | nConWatPum | 2 | Total number of condenser water pumps |
| Boolean | have_WSE | true | Flag to indicate if the plant has waterside economizer |
| Boolean | closeCoupledPlant | true | Flag to indicate if the plant is close coupled |
| Real | desCap | 1e6 | Plant design capacity |
| Real | fanSpeMin | 0.1 | Minimum tower fan speed |
| Setpoint | |||
| Real[nChi] | minChiLif | {12, 12} | Minimum LIFT of each chiller |
| Real[nChi] | TConWatSup_nominal | {293.15, 293.15} | Design condenser water supply temperature (condenser entering) of each chiller |
| Real[nChi] | TConWatRet_nominal | {303.15, 303.15} | Design condenser water return temperature (condenser leaving) of each chiller |
| Real[nChi] | TChiWatSupMin | {278.15, 278.15} | Lowest chilled water supply temperature of each chiller |
| Coupled plant › Controller | |||
| Buildings.Controls.OBC.CDL.Types.SimpleController | couPlaCon | Buildings.Controls.OBC.CDL.Types.SimpleController.PI | Type of controller |
| Real | kCouPla | 1 | Gain of controller |
| Real | TiCouPla | 0.5 | Time constant of integrator block |
| Real | TdCouPla | 0.1 | Time constant of derivative block |
| Real | yCouPlaMax | 1 | Upper limit of output |
| Real | yCouPlaMin | 0 | Lower limit of output |
| Less coupled plant › Return water temperature controller | |||
| Real | samplePeriod | 30 | Period of sampling condenser water supply and return temperature difference |
| Less coupled plant › Supply water temperature controller | |||
| Buildings.Controls.OBC.CDL.Types.SimpleController | supWatCon | Buildings.Controls.OBC.CDL.Types.SimpleController.PI | Type of controller |
| Real | kSupCon | 1 | Gain of controller |
| Real | TiSupCon | 0.5 | Time constant of integrator block |
| Real | TdSupCon | 0.1 | Time constant of derivative block |
| Real | ySupConMax | 1 | Upper limit of output |
| Real | ySupConMin | 0 | Lower limit of output |
| Advanced | |||
| Real | speChe | 0.01 | Lower threshold value to check fan or pump speed |
| Advanced › Enable tower | |||
| Real | cheMinFanSpe | 300 | Threshold time for checking duration when tower fan equals to the minimum tower fan speed |
| Real | cheMaxTowSpe | 300 | Threshold time for checking duration when any enabled chiller maximum cooling speed equals to the minimum tower fan speed |
| Real | cheTowOff | 60 | Threshold time for checking duration when there is no enabled tower fan |
| Advanced › Setpoint: Plant startup | |||
| Real | iniPlaTim | 600 | Time to hold return temperature to initial setpoint after plant being enabled |
| Real | ramTim | 180 | Time to ramp return water temperature from initial value to setpoint |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | uSpeWSE | Cooling tower speed when the waterside economizer is enabled | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanInput[nChi] | uChi | Chiller enabling status: true=ON | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanInput | uWse | Waterside economizer status: true=ON | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | reqPlaCap | Current required plant capacity | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput[nChi] | uMaxSpeSet | Maximum cooling tower speed setpoint from each chiller head pressure control loop | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanInput[nTowCel] | uTow | Cooling tower operating status: true=running tower cell | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | TChiWatSupSet | Chilled water supply setpoint temperature | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanInput | uPla | Plant enabling status | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | TConWatRet | Condenser water return temperature (condenser leaving) | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanInput[nConWatPum] | uConWatPum | Current condenser water pump status | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | TConWatSup | Condenser water supply temperature (condenser entering) | |
| Buildings.Controls.OBC.CDL.Interfaces.RealOutput | ySpeSet | Fan speed setpoint of each cooling tower cell | |
| Buildings.Controls.OBC.CDL.Interfaces.RealOutput | yLifMax | Maximum LIFT among enabled chillers | |
| Buildings.Controls.OBC.CDL.Interfaces.RealOutput | yLifMin | Minimum LIFT among enabled chillers | |
| Buildings.Controls.OBC.CDL.Interfaces.RealOutput | TConWatRetSet | Condenser water return temperature setpoint | |
| Buildings.Controls.OBC.CDL.Interfaces.RealOutput | TConWatSupSet | Condenser water supply temperature setpoint |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Towers.FanSpeed.ReturnWaterTemperature.Subsequences.Setpoint | conWatRetSet | Return temperature setpoint | |
| Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Towers.FanSpeed.ReturnWaterTemperature.Subsequences.Enable | enaTow | Enable and disable cooling tower fans | |
| Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Towers.FanSpeed.ReturnWaterTemperature.Subsequences.Coupled | couTowSpe | Tower fan speed control when the plant is close coupled | |
| Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Towers.FanSpeed.ReturnWaterTemperature.Subsequences.LessCoupled | lesCouTowSpe | Tower fan speed control when the plant is not close coupled |
Revisions
-
August 9, 2019, by Jianjun Hu:
First implementation.