Buildings.Controls.OBC.CDL.SetPoints

Package with blocks for setpoint resets

Information

This package contains components models to compute set points for control systems.

Package Content

Name	Description
SupplyReturnTemperatureReset	Block to compute the supply and return set point
Validation	Collection of models that validate the SetPoints blocks of the CDL

Buildings.Controls.OBC.CDL.SetPoints.SupplyReturnTemperatureReset

Block to compute the supply and return set point

Buildings.Controls.OBC.CDL.SetPoints.SupplyReturnTemperatureReset

Information

This block computes the set point temperatures for the supply and return water temperature. The set point for the zone air temperature can be an input to the model. It allows to use this model with systems that have night set back.

If used to reset the temperature in a heating system, the parameter dTOutHeaBal can be used to shift the heating curve to take into account that heat gains from solar, equipment and people make up for some of the transmission losses. For example, in energy efficient houses, the heating may not be switched on if the outside air temperature is greater than 12°C, even if a zone temperature of 20°C is required. In such a situation, set dTOutHeaBal=20-12=8 Kelvin to shift the heating curve.

Parameters

Type	Name	Default	Description
Real	m	1.3	Exponent for heat transfer
TemperatureDifference	dTOutHeaBal	8	Offset for heating curve [K]
Nominal conditions
Temperature	TSup_nominal		Supply temperature [K]
Temperature	TRet_nominal		Return temperature [K]
Temperature	TZon_nominal	293.15	Zone temperature [K]
Temperature	TOut_nominal		Outside temperature [K]

Connectors

Type	Name	Description
input RealInput	TSetZon	Zone setpoint temperature [K]
input RealInput	TOut	Outside temperature [K]
output RealOutput	TSup	Setpoint for supply temperature [K]
output RealOutput	TRet	Setpoint for return temperature [K]

Modelica definition

block SupplyReturnTemperatureReset "Block to compute the supply and return set point" parameter Real m = 1.3 "Exponent for heat transfer"; parameter Modelica.SIunits.Temperature TSup_nominal "Supply temperature"; parameter Modelica.SIunits.Temperature TRet_nominal "Return temperature"; parameter Modelica.SIunits.Temperature TZon_nominal = 293.15 "Zone temperature"; parameter Modelica.SIunits.Temperature TOut_nominal "Outside temperature"; parameter Modelica.SIunits.TemperatureDifference dTOutHeaBal(displayUnit="K") = 8 "Offset for heating curve"; Interfaces.RealInput TSetZon( final quantity="ThermodynamicTemperature", final unit = "K", displayUnit = "degC", min=200) "Zone setpoint temperature"; Interfaces.RealInput TOut( final quantity="ThermodynamicTemperature", final unit = "K", displayUnit = "degC", min=200) "Outside temperature"; Interfaces.RealOutput TSup( final quantity="ThermodynamicTemperature", final unit = "K", displayUnit = "degC", min=200) "Setpoint for supply temperature"; Interfaces.RealOutput TRet( final quantity="ThermodynamicTemperature", final unit = "K", displayUnit = "degC", min=200) "Setpoint for return temperature"; protected parameter Modelica.SIunits.Temperature TOutOffSet_nominal = TOut_nominal + dTOutHeaBal "Effective outside temperature for heat transfer at nominal conditions (takes into account zone heat gains)"; Real qRel "Relative heating load = Q_flow/Q_flow_nominal"; Modelica.SIunits.Temperature TOutOffSet "Effective outside temperature for heat transfer (takes into account zone heat gains)"; equation TOutOffSet = TOut + dTOutHeaBal; // Relative heating load, compared to nominal conditions qRel = max(0, (TSetZon-TOutOffSet)/(TZon_nominal-TOutOffSet_nominal)); TSup = TSetZon + ((TSup_nominal+TRet_nominal)/2-TZon_nominal) * qRel^(1/m) + (TSup_nominal-TRet_nominal)/2 * qRel; TRet = TSup - qRel * (TSup_nominal-TRet_nominal); end SupplyReturnTemperatureReset;