User's Guide


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The package Buildings.Controls.OBC contains the Control Description Language (CDL) and models for building control that are implemented using CDL. Both have been developed in the OpenBuildingControl project, see

The package contains control sequences for

The control sequences are composed of the elementary blocks from the package Buildings.Controls.OBC.CDL.

The package also contains models for unit conversions, Buildings.Controls.OBC.UnitConversions, and utilities models, such as Buildings.Controls.OBC.Utilities.OptimalStart, which output the optimal start time for an HVAC system.

The Control Description Language (CDL) can be found in Buildings.Controls.OBC.CDL and its specification is at

Extends from Modelica.Icons.Information (Icon for general information packages).

Package Content

Name Description
Buildings.Controls.OBC.UsersGuide.Conventions Conventions Naming conventions in OBC package

Buildings.Controls.OBC.UsersGuide.Conventions Buildings.Controls.OBC.UsersGuide.Conventions

Naming conventions in OBC package


The Buildings.Controls.OBC package follows the naming conventions of the Buildings Library, see Buildings.UsersGuide.Conventions. The table below shows some examples of commonly used names. Note that the names are generally composed as follows:

Generally, we strive for short names, and therefore often prefix or postfix are omitted if the type of the variable is clear from the context. For example, a room temperature thermostat may simply use T as an input as it is clear that this will be the room temperature.

Instance names
TOut (hOut) Outdoor air temperature (enthalpy)
TZonHeaSet (TZonCooSet) Zone heating (cooling) set point temperature
VDis_flow Measured discharge airflow rate
dpBui Building static pressure difference, relative to ambient
uOpeMod Zone group operating mode
uResReq Number of reset requests
uSupFan Current supply fan enabling status, true: fan is enabled
uSupFanSpe Current supply fan speed
uDam Measured damper position
uHea (uCoo) Heating (cooling) loop signal
yPosMin (yPosMax) Minimum (maximum) position
yHeaCoi (yCooCoi) Heating (cooling) coil control signal
uChiIsoVal Chiller condenser water isolation valve status
dpChiWat_remote Chilled water differntial statis pressure from remote sensor
TChiWatRet Chilled water return temperature
VChiWat_flow Measured chilled water volume flow rate
uHeaPreCon Chiller head pressure control loop signal from chiller controller
yChiPumSpe Chilled water pump speed setpoint
yChi Chiller status setpoint
yMinValPos Minimum valve position setpoint
Parameter names
Name Comments
use_TMix Set to true if mixed air temperature measurement is used
have_occSen (have_winSen) Set to true if the zone has occupancy (window) sensor
AFlo Area of the zone
VDisHeaSetMax_flow (VDisCooSetMax_flow) Zone maximum heating (cooling) airflow set point
VOutPerAre_flow (VOutPerPer_flow) Outdoor airflow rate per unit area (person)
V_flow_nominal Nominal volume flow rate
VOutMin_flow Calculated minimum outdoor airflow rate at design stage
pMinSet (pMaxSet) Minimum (maximum) pressure set point for fan speed control
TSupSetMin (TSupSetMax) Lowest (Highest) cooling supply air temperature
TOccHeaSet (TUnoHeaSet) Zone occupied (unoccupied) heating set point
TZonCooMax (TZonCooMin) Maximum (minimum) zone cooling set point when cooling is on
retDamPhyPosMax (outDamPhyPosMax) Physically fixed maximum position of the return (outdoor) air damper
samplePeriod Sample period
zonDisEffHea (zonDisEffCoo) Zone air distribution effectiveness during heating (cooling)
kCoo Gain for cooling control loop signal
TiCoo Time constant of integrator block for cooling control loop signal
TdCoo Time constant of derivative block for cooling control loop signal
nChi Total number of chillers
have_parChi True: the plant has parallel chillers
have_heaChiWatPum True: the plant has headed chilled water pumps
have_fixSpeConWatPum True: the plant has fixed speed condenser water pumps
need_reduceChillerDemand True: the plant needs to limit chiller demand when chiller staging
minChiLif Minimum allowable lift at minimum load for chiller
TChiWatSupMin Minimum chilled water supply temperature
dpChiWatPumMin Minimum chilled water pump differential static pressure
lift_min Chiller minimum lift

Extends from Modelica.Icons.Information (Icon for general information packages).

Modelica definition

class Conventions "Naming conventions in OBC package" extends Modelica.Icons.Information; end Conventions;