This component is available in the kitControl palette Energy folder. It uses the two sets of temperature and humidity inputs to find the air supply with the least amount of heat when
the purgeEnabled input is true. The freeCooling output will be set to false if outside >= inside or set to true if outside = nightSetpoint.
For inside and outside comparisons, you can select either temperature or enthalpy comparisons. There is also a low temperature check to protect against freezing.
The NightPurge component includes the following properties:
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Temperature Facets
Specifies the units and number precision of the Outside Temp, Inside Temp, and Low Temperature Limit properties.
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Humidity Facets
Specifies the units and number precision of the Outside Humidity and Inside Humidity properties.
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Purge Enabled
StatusBoolean, must be true to enable night purge operation. Whenever false, the Free Cooling output is set to the opposite of the Free Cooling Command (or null, if Use Null Output is set to true), and the Current Mode slot value is “Disabled.”
Often, Purge Enabled is linked to a “Not” object sourced from a BooleanSchedule output.
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Outside Temp
Input for the current outside air temperature. This input must be valid for this object to function.
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Outside Humidity
Input for the current outside air humidity. This input must be valid for this object to function.
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Inside Temp
Input for the current inside air temperature. This input must be valid for this object to function.
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Inside Humidity
Input for the current inside air humidity. This input must be valid for this object to function.
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Low temperature Limit
This property is used to provide freeze protection.
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Night Setpoint
Inside night temperature setpoint, at or below which free cooling is not applied. Instead, the Current Mode is set to “Satisfied.”
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Outside Enthalpy
This is the calculated outside air enthalpy.
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Inside Enthalpy
This is the calculated inside air enthalpy.
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Free Cooling
A StatusBoolean output set to value of the Free Cooling Command when it is determined that free cooling should be used. Otherwise, the value is set to the opposite state, or null (if Use Null Output is set to true).
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Current Mode
This enumeration indicates which of the following modes this object is currently in:
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Disabled (Purge Enabled is false)
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Free Cooling
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No Free Cooling (free cooling not available)
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Low temperature (Outside Temp below Low Temperature Limit, free cooling disabled)
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Input error (A temperature or humidity is invalid (down, fault, etc.), free cooling disabled)
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Satisfied (Inside temperature below Night Setpoint, free cooling disabled)
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Setpoint Deadband
Temperature setpoint deadband applied when inside temperature falls below Night Setpoint, before free cooling can be enabled. Default value is 1.0.
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Threshold Span
The difference between the inside enthalpy and the outside enthalpy must be greater than this value before free cooling will be enabled. Default value is 1.0.
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Use Enthalpy
Setting this property to true will enable the use of enthalpy for determining if free cooling is available. Otherwise, it will just use outside and inside temperature to decide.
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Free Cooling Command
If it is determined that free cooling is available, this is the boolean value that will be set in the Free Cooling output.
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Use Null Output
If this property is true, then the null flag will also be set on the Free Cooling output when free cooling is not available.
The following illustrations show some example property sheet and wiresheet views of the NightPurge component usage.
