blockSupplyReturnTemperatureReset

Block to compute the supply and return set point
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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.

Typical usage

The figure below shows a typical usage for a hot water temperature reset for a heating system. The parameters of the block heaCur are for a heating system with 60°C supply water temperature and 40°C return water temperature at an outside temperature of -10°C and a room temperature of 20°C. The offset for the temperature reset is 8 Kelvin, i.e., above 12°C outside temperature, there is no heating load. The figure shows the computed supply and return water temperatures.

Supply and return water temperatures.

Parameters

TypeNameDefaultDescription
Realm1.3Exponent for heat transfer
RealdTOutHeaBal8Offset for heating curve
Nominal conditions
RealTSup_nominalSupply temperature
RealTRet_nominalReturn temperature
RealTZon_nominal293.15Zone temperature
RealTOut_nominalOutside temperature

Connectors

TypeNameDefaultDescription
CDL.Interfaces.RealInputTSetZonZone setpoint temperature
CDL.Interfaces.RealInputTOutOutside temperature
CDL.Interfaces.RealOutputTSupSetpoint for supply temperature
CDL.Interfaces.RealOutputTRetSetpoint for return temperature

Revisions

  • October 21, 2021, by Michael Wetter:
    Corrected icon.
  • February 8, 2021, by Michael Wetter:
    Renamed to Buildings.Controls.OBC.Utilities.SetPoints.SupplyReturnTemperatureReset and reimplemented using elementary CDL blocks.
    This is for Buildings, issue 2355.
  • November 12, 2020, by Michael Wetter:
    Reformulated to remove dependency to Modelica.Units.SI.
    This is for Buildings, issue 2243.
  • January 3, 2020, by Jianjun Hu:
    Changed name from HotWaterTemperatureReset to SupplyReturnTemperatureReset. This is for Buildings, issue 860.
  • January 10, 2017, by Milica Grahovac:
    First CDL implementation.
  • May 29, 2014, by Michael Wetter:
    Removed undesirable annotation Evaluate=true.
  • February 13, 2013, by Michael Wetter:
    Corrected error that led to wrong results if the zone air temperature is different from its nominal value TZon_nominal. See ticket Buildings, issue 74.
  • November 21, 2011, by Michael Wetter:
    Improved documentation.
  • February 5, 2009 by Michael Wetter:
    First implementation.