blockController
Tower fan speed control
Information
Block that outputs cooling tower fan speed ySpeSet. This is implemented
according to ASHRAE Guideline 36-2021, section 5.20.12.2, item a and c.
These sections specify sequences to control tower fan speed in the mode
when waterside economizer (if the plant does have it) is enabled or disabled, for
maintaining condenser water return temperature at its setpoint. This control is
used for plants with dynamic load profiles, i.e., those for which PLR may change
by more than approximately 25% in any hour.
It includes two subsequences:
- Sequence of controlling tower fan speed when waterside economizer is enabled, see Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Towers.FanSpeed.EnabledWSE.Controller for a description.
- Sequence of controlling the tower fan speed to maintain the condenser water return temperature at its setpoint. This control would be disabled if the waterside economizer is enabled. See Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Towers.FanSpeed.ReturnWaterTemperature.Controller 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 |
| Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Types.TowerSpeedControl | fanSpeCon | Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Types.TowerSpeedControl.CondenserWaterReturnTemperaure | Tower fan speed control type |
| Boolean | have_conWatRetCon | fanSpeCon == Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Types.TowerSpeedControl.CondenserWaterReturnTemperaure | True: the fan speed is controlled to maintain the condenser water return temperature setpoint |
| Boolean | closeCoupledPlant | true | Flag to indicate if the plant is close coupled |
| Boolean | have_WSE | true | Flag to indicate if the plant has waterside economizer |
| Real | desCap | 1e6 | Plant design capacity |
| Real | fanSpeMin | 0.1 | Minimum tower fan speed |
| WSE Enabled › Integrated | |||
| Real[nChi] | chiMinCap | {1e4, 1e4} | Minimum cyclining load below which chiller will begin cycling |
| Buildings.Controls.OBC.CDL.Types.SimpleController | intOpeCon | Buildings.Controls.OBC.CDL.Types.SimpleController.PI | Type of controller |
| Real | kIntOpe | 1 | Gain of controller |
| Real | TiIntOpe | 0.5 | Time constant of integrator block |
| Real | TdIntOpe | 0.1 | Time constant of derivative block |
| WSE Enabled › WSE-only | |||
| Buildings.Controls.OBC.CDL.Types.SimpleController | chiWatCon | Buildings.Controls.OBC.CDL.Types.SimpleController.PI | Type of controller |
| Real | kWSE | 1 | Gain of controller |
| Real | TiWSE | 0.5 | Time constant of integrator block |
| Real | TdWSE | 0.1 | Time constant of derivative block |
| Return temperature control › 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 |
| Return temperature control › Coupled plant | |||
| 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 |
| Return temperature control › Less coupled plant | |||
| Real | samplePeriod | 30 | Period of sampling condenser water supply and return temperature difference |
| 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 | 0.005 | Lower threshold value to check fan or pump speed |
| Advanced › Return temperature control: 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 › Return temperature control: Setpoint | |||
| 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 | uChiLoa | Current cooling load | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanInput[nChi] | uChi | Chiller enabling status: true=ON | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanInput | uWse | Waterside economizer enabling status: true=ON | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | TChiWatSup | Chilled water supply temperature | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | TChiWatSupSet | Chilled water supply temperature setpoint | |
| 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 cell operating status: true=running tower cell | |
| 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.Controller | fanSpeRetTem | Fan speed control based on condenser water return temperature control | |
| Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Towers.FanSpeed.EnabledWSE.Controller | fanSpeWse | Tower fan speed when waterside economizer is enabled | |
| Buildings.Controls.OBC.CDL.Logical.Sources.Constant | con1 | Check if the speed control is for returning water temperature | |
| Buildings.Controls.OBC.CDL.Utilities.Assert | assMes | Tower speed control warning |
Revisions
-
September 14, 2019, by Jianjun Hu:
First implementation.