Curve:Linear
Curve:Quadratic
Curve:Cubic
Curve:Quartic
Curve:Exponent
Curve:Bicubic
Curve:Biquadratic
Curve:RectangularHyperbola2
Curve:DoubleExponentialDecay
Used in many HVAC components as well as electrical storage devices
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Curve:Linear Curve:Quadratic Curve:Cubic Curve:Quartic Curve:Exponent Curve:Bicubic Curve:Biquadratic Curve:RectangularHyperbola2 Curve:DoubleExponentialDecay |
Used in many HVAC components as well as electrical storage devices |
This group of objects primarily consists of polynomial curves that are used to characterize the performance of HVAC equipment. Several other non-polynomial curves are also included to characterize the performance of pumps and fans. The curves are usually derived from fits or regressions to data covering a limited range. Results for independent variable values outside this range are likely to be invalid, so curve input always contains a range of validity (maximum and minimum permitted values) for each independent variable and can optionally have limits on the curve output. No error or warning message is issued if an independent variable is outside the range. Instead, EnergyPlus uses the minimum value if an independent variable is less than the minimum, and the maximum if a variable exceeds the maximum. Similarly, no error or warning message is issued if the curve output is outside the range of the optional minimum and maximum curve output limits. Instead, EnergyPlus uses the minimum and maximum curve limits to cap the output of the performance curve.
Tip: The EnergyPlus Curve Fit Tool can be used to generate HVAC performance curves in the format required by EnergyPlus.
The curve data follow a similar pattern and all have the same first 4 data items:
A user assigned unique name for a curve. When a curve is used, it is referenced by this name.
Specific information about the curve.
Where the curve was derived from (usually either EnergyPlus, meaning it comes from the EnergyPlus curves database, which is largely derived from the DOE-2 database, or DesignBuilder meaning that the curve is provided by DesignBuilder Software)
The category can be one of:
The rest of the data depends on the category as described below.
Input for the linear curve consists of a curve name, the two coefficients, and the maximum and minimum valid independent variable values. Optional inputs for curve minimum and maximum may be used to limit the output of the performance curve (e.g. limit extrapolation). The equation represented by the linear curve is:
y = C1 + C2 * x
The constant coefficient (C1) in the equation.
The linear coefficient (C2) in the equation.
The minimum allowable value of x. Values of x less than the minimum will be replaced by the minimum.
The maximum allowable value of x. Values of x greater than the maximum will be replaced by the maximum.
The minimum allowable value of the evaluated curve. Values less than the minimum will be replaced by the minimum.
The maximum allowable value of the evaluated curve. Values greater than the maximum will be replaced by the maximum.
This field is used to indicate the kind of units that may be associated with the x values. It is used by editor to display the appropriate SI and IP units for the Minimum Value of X and Maximum Value of x. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
This field is used to indicate the kind of units that may be associated with the output values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Curve Output and Maximum Curve Output. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
Input for a quadratic curve consists of the curve name, the three coefficients, and the maximum and minimum valid independent variable values. Optional inputs for curve minimum and maximum may be used to limit the output of the performance curve (e.g. limit extrapolation). The equation represented by the quadratic curve is:
y = C1 + C2 * x + C3 * x2
The constant coefficient (C1) in the equation.
The linear coefficient (C2) in the equation.
The quadratic coefficient (C3) in the equation.
The minimum allowable value of x. Values of x less than the minimum will be replaced by the minimum.
The maximum allowable value of x. Values of x greater than the maximum will be replaced by the maximum.
The minimum allowable value of the evaluated curve. Values less than the minimum will be replaced by the minimum.
The maximum allowable value of the evaluated curve. Values greater than the maximum will be replaced by the maximum.
This field is used to indicate the kind of units that may be associated with the x values. It is used by editor to display the appropriate SI and IP units for the Minimum Value of x and Maximum Value of x. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
This field is used to indicate the kind of units that may be associated with the output values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Curve Output and Maximum Curve Output. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
Input for a cubic curve consists of the curve name, the 4 coefficients, and the maximum and minimum valid independent variable values. Optional inputs for curve minimum and maximum may be used to limit the output of the performance curve (e.g. limit extrapolation). The equation represented by the cubic curve is:
y = C1 + C2 * x + C3 * x2 + C4 * x3
The constant coefficient (C1) in the equation.
The linear coefficient (C2) in the equation.
The quadratic coefficient (C3) in the equation.
The quadratic coefficient (C4) in the equation.
The minimum allowable value of x. Values of x less than the minimum will be replaced by the minimum.
The maximum allowable value of x. Values of x greater than the maximum will be replaced by the maximum.
The minimum allowable value of the evaluated curve. Values less than the minimum will be replaced by the minimum.
The maximum allowable value of the evaluated curve. Values greater than the maximum will be replaced by the maximum.
This field is used to indicate the kind of units that may be associated with the x values. It is used by editor to display the appropriate SI and IP units for the Minimum Value of x and Maximum Value of x. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
This field is used to indicate the kind of units that may be associated with the output values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Curve Output and Maximum Curve Output. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
Input for a exponent curve consists of the curve name, the 3 coefficients, and the maximum and minimum valid independent variable values. Optional inputs for curve minimum and maximum may be used to limit the output of the performance curve (e.g. limit extrapolation). The equation represented by the exponent curve is:
y = C1 + C2 * xC3
The constant coefficient (C1) in the equation.
The linear coefficient (C2) in the equation.
The exponent coefficient (C3) in the equation.
The minimum allowable value of x. Values of x less than the minimum will be replaced by the minimum.
The maximum allowable value of x. Values of x greater than the maximum will be replaced by the maximum.
The minimum allowable value of the evaluated curve. Values less than the minimum will be replaced by the minimum.
The maximum allowable value of the evaluated curve. Values greater than the maximum will be replaced by the maximum.
This field is used to indicate the kind of units that may be associated with the x values. It is used by editor to display the appropriate SI and IP units for the Minimum Value of x and Maximum Value of x. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
This field is used to indicate the kind of units that may be associated with the output values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Curve Output and Maximum Curve Output. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
This curve is a function of two independent variables. Input consists of the curve name, the six coefficients, and min and max values for each of the independent variables. Optional inputs for curve minimum and maximum may be used to limit the output of the performance curve (e.g. limit extrapolation). The equation represented by the biquadratic curve is:
z = C1 + C2 * x + C3 * x2 + C4* y + C5 * y2 + C6*xy
The constant coefficient (C1) in the equation.
The linear coefficient (C2) in the equation.
The quadratic coefficient (C3) in the equation.
The coefficient C4 in the equation.
The coefficient C5 in the equation.
The coefficient C6 in the equation.
The minimum allowable value of x. Values of x less than the minimum will be replaced by the minimum.
The maximum allowable value of x. Values of x greater than the maximum will be replaced by the maximum.
The minimum allowable value of y. Values of y less than the minimum will be replaced by the minimum.
The maximum allowable value of y. Values of y greater than the maximum will be replaced by the maximum.
The minimum allowable value of the evaluated curve. Values less than the minimum will be replaced by the minimum.
The maximum allowable value of the evaluated curve. Values greater than the maximum will be replaced by the maximum.
This field is used to indicate the kind of units that may be associated with the x values. It is used by editor to display the appropriate SI and IP units for the Minimum Value of x and Maximum Value of x. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
This field is used to indicate the kind of units that may be associated with the y values. It is used by editor to display the appropriate SI and IP units for the Minimum Value of y and Maximum Value of y. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
This field is used to indicate the kind of units that may be associated with the output values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Curve Output and Maximum Curve Output. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
This curve type is a function of two independent variables. Input consists of the curve name, the ten coefficients, and the minimum and maximum values for each of the independent variables. Optional inputs for curve minimum and maximum may be used to limit the output of the performance curve (e.g. limit extrapolation). The equation represented by the bicubic curve is:
z = C1 + C2 * x + C3* x2 + C4* y + C5 * y2 + C6*xy + C7* x3 + C8* y3 + C9 * x2y + C10 * xy2
The constant coefficient (C1) in the equation.
The linear coefficient (C2) in the equation.
The quadratic coefficient (C3) in the equation.
The coefficient C4 in the equation.
The coefficient C5 in the equation.
The coefficient C6 in the equation.
The coefficient C7 in the equation.
The coefficient C8 in the equation.
The coefficient C9 in the equation.
The coefficient C10 in the equation.
The minimum allowable value of x. Values of x less than the minimum will be replaced by the minimum.
The maximum allowable value of x. Values of x greater than the maximum will be replaced by the maximum.
The minimum allowable value of y. Values of y less than the minimum will be replaced by the minimum.
The maximum allowable value of y. Values of y greater than the maximum will be replaced by the maximum.
The minimum allowable value of the evaluated curve. Values less than the minimum will be replaced by the minimum.
The maximum allowable value of the evaluated curve. Values greater than the maximum will be replaced by the maximum.
This field is used to indicate the kind of units that may be associated with the x values. It is used by editor to display the appropriate SI and IP units for the Minimum Value of X and Maximum Value of x. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
This field is used to indicate the kind of units that may be associated with the y values. It is used by editor to display the appropriate SI and IP units for the Minimum Value of y and Maximum Value of y. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
This field is used to indicate the kind of units that may be associated with the output values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Curve Output and Maximum Curve Output. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
Input for a Quartic (fourth order polynomial) curve consists of the curve name, the five coefficients, and the maximum and minimum valid independent variable values. Optional inputs for curve minimum and maximum may be used to limit the output of the performance curve (e.g., limit extrapolation). The equation represented by the quartic curve is:
y = C1 + C2 * x + C3 * x2 + C4 * x3 + C5 * x4
The constant coefficient (C1) in the equation.
The linear coefficient (C2) in the equation.
The quadratic coefficient (C3) in the equation.
The cubic coefficient (C4) in the equation.
The fourth-order coefficient (C5) in the equation.
The minimum allowable value of x. Values of x less than the minimum will be replaced by the minimum.
The maximum allowable value of x. Values of x greater than the maximum will be replaced by the maximum.
The minimum allowable value of the evaluated curve. Values less than the minimum will be replaced by the minimum.
The maximum allowable value of the evaluated curve. Values greater than the maximum will be replaced by the maximum.
This field is used to indicate the kind of units that may be associated with the x values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Value of X and Maximum Value of x. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
This field is used to indicate the kind of units that may be associated with the output values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Curve Output and Maximum Curve Output. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
Input for the single rectangular hyperbola type 2 curve consists of the curve name, the three coefficients, and the maximum and minimum valid independent variable values. Optional inputs for the curve minimum and maximum may be used to limit the output of the performance curve (e.g., limit extrapolation). The equation is:
y = (C1* x) / (C2 + x) + C3* x
The required numeric constant coefficient C1 in the equation.
The required numeric constant coefficient C2 in the equation.
The required numeric constant coefficient C3 in the equation.
The required numeric minimum allowable value of x. Values of x less than the minimum will b e replaced by the minimum.
The required numeric maximum allowable value of x. Values of x greater than the maximum will be replaced by the maximum.
The optional numeric minimum allowable value of the evaluated curve. Values less than the minimum will be replaced by the minimum.
The optional numeric maximum allowable value of the evaluated curve. Values greater than the maximum will be replaced by the maximum.
This optional field is provided for future purposes so that DesignBuilder could display the appropriate SI or IP units for the Minimum Value of x and Maximum Value of x (currently dimensionless). At this time, only the Dimensionless option is provided so that no unit conversion is used for this curve.
This optional field is provided for future purposes so that DesignBuilder could display the appropriate SI or IP units for the Minimum Curve Output and Maximum Curve Output (currently dimensionless). At this time, only the Dimensionless option is provided so that no unit conversion is used for this curve.
Input for the double exponential decay curve consists of the curve name, the five coefficients, and the maximum and minimum valid independent variable values. Optional inputs for the curve include the minimum and maximum output of the performance curve. The equation is:
y = C1 + C2 exp( C3 x) + C4 exp(C5 x)
The required numeric constant coefficient C1 in the equation.
The required numeric constant coefficient C2 in the equation.
The required numeric constant coefficient C3 in the equation.
The required numeric constant coefficient C4 in the equation.
The required numeric constant coefficient C5 in the equation.
The required numeric minimum allowable value of x. Values of x less than the minimum will be replaced by the minimum
The required numeric maximum allowable value of x. Values of x greater than the maximum will be replaced by the maximum
The optional numeric minimum allowable value of the evaluated curve. Values less than the minimum will be replaced by the minimum
The optional numeric maximum allowable value of the evaluated curve. Values greater than the maximum will be replaced by the maximum.
The optional field is provided for future purposes so that DesignBuilder could display the appropriate SI or IP units for the Minimum and Maximum Value of x. Currently, only Dimensionless option is provided so that no unit conversion is used for this curve
The optional field is provided for future purposes so that DesignBuilder could display the appropriate SI or IP units for the Minimum and Maximum Curve Ouput. Currently, only Dimensionless option is provided so that no unit conversion is used for this curve.