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Infiltration is the unintended flow of air from the outdoor environment directly into a thermal zone. Infiltration is generally caused by the opening and closing of exterior doors, cracks around windows, and even in very small amounts through building elements. The basic equation used to calculate infiltration with this object is:
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Infiltration is the unintended flow of air from the outdoor environment directly into a thermal zone. Infiltration is generally caused by the opening and closing of exterior doors, cracks around windows and exterior doors, and even in very small amounts through building elements. The basic equation used to calculate infiltration with this object is:
More advanced infiltration calculations are possible using the EnergyPlus AirflowNetwork model for natural infiltration driven by wind and/or by forced air. Infiltration described by the equation shown above is entered into EnergyPlus using the following syntax. Exfiltration (the leakage of zone air to the outside) is generally handled better as zone exhaust air in the zone equipment description. The equation must always yield a non-negative results; negative values are set to 0.0.
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The question of typical values for these coefficients is subject to debate. Ideally, one should do a detailed analysis of the infiltration situation and then determine a custom set of coefficients using methods such as those laid out in Chapter 26 of the ASHRAE Handbook of Fundamentals. The EnergyPlus defaults are 1,0,0,0 which give a constant volume flow of infiltration under all conditions.
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The question of typical values for these coefficients is subject to debate. Ideally, one should do a detailed analysis of the infiltration situation and then determine a custom set of coefficients using methods such as those laid out in Chapter 26 of the ASHRAE Handbook of Fundamentals. The EnergyPlus defaults are 1,0,0,0 which give a constant volumetric flow of infiltration under all conditions.
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BLAST (one of the EnergyPlus predecessors) used the following values as defaults: 0.606, 0.03636, 0.1177, 0. These coefficients produce a value of 1.0 at 0$^\circ$C deltaT and 3.35 m/s (7.5 mph) windspeed, which corresponds to a typical summer condition. At a winter condition of 40$^\circ$C deltaT and 6 m/s (13.4 mph) windspeed, these coefficients would increase the infiltration rate by a factor of 2.75.
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BLAST (one of the EnergyPlus predecessors) used the following values as defaults: 0.606, 0.03636, 0.1177, 0. These coefficients produce a value of 1.0 at 0$^\circ$C temperature difference between the inside and outside air temperatures and 3.35 m/s (7.5 mph) windspeed, which corresponds to a typical summer condition. At a winter condition of 40$^\circ$C temperature difference between the inside and outside air temperatures and 6 m/s (13.4 mph) windspeed, these coefficients would increase the infiltration rate by a factor of 2.75.
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In DOE-2 (the other EnergyPlus predecessor), the air change method defaults are (adjusted to SI units) 0, 0, 0.224 (windspeed), 0. With these coefficients, the summer conditions above would give a factor of 0.75, and the winter conditions would give 1.34. A windspeed of 4.47 m/s (10 mph) gives a factor of 1.0.
The local outdoor dry-bulb temperature used in the above basic equation (T\(_{odb}\)) is typically a function of the height of the zone centroid above ground. The corresponding zone name is given in the second field. The local outdoor dry-bulb temperature calculation procedure is given in the section of ``Local Outdoor Air Temperature Calculation'' in the Engineering Reference.
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The local outdoor wind speed used in the above basic equation (WindSpeed) is also a function of the height of the zone centroid above ground. The corresponding zone name is given in the second filed. The local outdoor wind speed calculation procedure is given in the section of ``Local Wind Speed Calculation'' in the Engineering Reference.
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The local outdoor wind speed used in the above basic equation (WindSpeed) is also a function of the height of the zone centroid above ground. The corresponding zone name is given in the second field. The local outdoor wind speed calculation procedure is given in the section of ``Local Wind Speed Calculation'' in the Engineering Reference.
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\begin{callout}
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Note: When the value of the Wind Speed Profile Exponent field in the \hyperref[siteheightvariation]{Site:HeightVariation} is equal to 0.0. The local wind speed is always equal to the wind speed given in the weather data and will not be dependent on zone centroid height. Similarly, if the value of the Air Temperature Gradient Coefficient is set equal to 0 the local air dry-bulb temperature is also always equal to the air dry-bulb temperature given in the weather data and will not be dependent on zone centroid height.
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Note: When the value of the Wind Speed Profile Exponent field in the \hyperref[siteheightvariation]{Site:HeightVariation} is equal to 0.0, the local wind speed is always equal to the wind speed given in the weather data and will not be dependent on zone centroid height. Similarly, if the value of the Air Temperature Gradient Coefficient is set equal to 0, the local air dry-bulb temperature is also always equal to the air dry-bulb temperature given in the weather data and will not be dependent on zone centroid height.
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\end{callout}
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One or more infiltration objects can be defined for each zone, and the resulting infiltration rate for the zone will simply be the summation of the flow rates specified by the infiltration objects.
This numeric field defines the crankcase heater capacity in Watts. When the outdoor air dry-bulb temperature is below the value specified in the input field Maximum Outdoor Dry-bulb Temperature for Crankcase Heater Operation (described below), the crankcase heater is enabled during the time that the compressor is not running. If this cooling coil is used as part of an air-to-air heat pump (Ref. AirLoopHVAC:UnitaryHeatPump:AirToAir or PackageTerminal: HeatPump:AirToAir), the crankcase heater defined for this DX cooling coil is ignored and the crankcase heater power defined for the DX heating coil (Ref. Coil:Heating:DX:SingleSpeed) is enabled during the time that the compressor is not running for either heating or cooling. The value for this input field must be greater than or equal to 0, and the default value is 0. To simulate a DX cooling coil without a crankcase heater, enter a value of 0.
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\paragraph{Field: Crankcase Heater Capacity Function of Temperature Curve Name}
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The name of a normalized Curve:* or Table:Lookup object encoding the relationship between the crankcase heater capacity and the outdoor air temperature. This curve can be any uni-variate curve or table. The output of this curve is multiplied by the value in the field ``Crankcase Heater Capacity'. If this field is missing or empty, constant crankcase heater capacity will be
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assumed.
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\paragraph{Field: Minimum Outdoor Dry-Bulb Temperature for Compressor Operation}
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This numeric field defines the minimum outdoor air dry-bulb temperature where the cooling coil compressor turns off. If this input field is left blank, the default value is -25 °C (-13 °F).
If there are 3 operating modes, it represents a subcool-reheat mode coil. The Operating Mode 1 represents a base operating mode coil. The Operating Mode 2 represents a subcool mode coil with lower SHR than the Operating Mode 1. The Operating Mode 3 represents a reheat mode coil with lower SHR than the Operating Mode 2. All 3 operation modes work together to represent a subcool reheat coil model. The operation procedure is described in \ref{coilcoolingdx}
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\paragraph{Field: Crankcase Heater Capacity Function of Temperature Curve Name}\label{outdoor-temperature-dependent-crankcase-heater-capacity-curve-name-0}
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The name of a normalized Curve:* or Table:Lookup object encoding the
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relationship between the crankcase heater capacity and the outdoor air
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temperature. This curve can be any uni-variate curve or table. The output of
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this curve is multiplied by the value in the field ``Crankcase Heater Capacity'.
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If this field is missing or empty, constant crankcase heater capacity will be
This object defines DX cooling coil performance for a single operating mode at rated conditions. Each operating mode may have one or more speeds, which are defined using the Coil:Cooling:DX:CurveFit:Speed object. Each operation mode can reference a maximum of 10 Coil:Cooling:DX:CurveFit:Speed objects.
When the DElight Daylighting Method is used, there may be up to a maximum of 100 reference points for each zone. Each Reference Point that is input does NOT need to be included in the control of the electric lighting system within the zone. This is determined by the fraction of the zone controlled by each Reference Point, which can be input as 0. Note when the DElight Daylighting Method is used, that the sum of all Reference Point control fractions must equal 1 to obtain correct overall results.
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It should also be noted that daylighting factors cannot be accurately calculated for reference points that are very close to a wall or window (less than 0.15 m or 6 inches). While an error is reported for a reference point that is too close to a window, no error message is generated when the user defines a point that is too close to a wall.
The Output:IlluminanceMap object expands on the reporting capabilities of the daylighting simulation. For any space or zone simulated with \hyperref[daylightingcontrols-000]{Daylighting:Controls}, the illuminance map can generate up to 2,500 points of additional daylighting illuminance values. The resulting map is output as a comma delimited text file that can be imported into a spreadsheet program for rapid visualization of the daylighting illuminance patterns in a space or zone. The values are produced on an hourly basis. The Z height of the map is constant (parallel to a flat floor). More than one illuminance map can be created for a space or zone. IlluminanceMap output is available only when SplitFlux daylighting method is selected in \hyperref[daylightingcontrols-000]{Daylighting:Controls} object.
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When using the Output:IlluminanceMap object, the user should note the following:
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\begin{itemize}
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\item Daylighting factors cannot be accurately calculated for reference points that are very close to a wall or window (less than 0.15 m or 6 inches). An error is reported for a reference point that is too close to a window, but no error is reported for a point that is too close to a wall.
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\item Since not all zones are rectangular, it is possible to have map points that are outside the zone. Any illuminance registered at these points is inaccurate and, additionally, a ``*'' marks these values for easy observance.
The number of daylighting reference points in the Y direction from the minimum to the maximum boundaries. The maximum number of points that can be generated is 2500 (Number of X Grid Points X Number of Y Grid Points).
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Note:~ Daylighting factors cannot be accurately calculated for reference points that are very close to a wall or window (less than 0.15 m or 6 inches). An error is reported for a reference point that is too close to a window, but no error is reported for a point that is too close to a wall.
Since not all zones are rectangular, it is possible to have map points that are outside the zone. Any illuminance registered at these points is inaccurate and, additionally, a ``*'' marks these values for easy observance.
This object specifies the ``style'' for the illuminance map output (described in the Output Details and Examples document). As described early in the document (see: EnergyPlus Output Processing), the user may select the ``style'' for the daylighting illuminance map output file (eplusmap.\textless{}ext\textgreater{}).
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