The OptStartStop component allows you to use Start Time Optimization and Stop Time Optimization to save energy. This component uses a space temperature input and area characteristics to calculate an optimal amount of lead-time before a scheduled event. It can analyze area temperature changes and adjust the optimization parameters based on the actual temperature change rates after an optimized start or stop.
The OptStartStop component is available in the vykonPro energy folder.
The two basic optimization types are described, as follows:
Start time optimization
This type of optimization reduces energy consumption by turning on equipment at the latest possible time that still allows for providing a comfortable temperature by occupancy time.
Stop time optimization
This type of optimization turns equipment off at the earliest possible time that allows the building to drift and stay within a temperature comfort range until the end of occupancy time.
See the following sections for additional details:
The OptStartStop calculation is performed at 15 seconds after the beginning of every minute, when the appropriate Start Enable or Stop Enable properties are set to true, a valid schedule event is linked to the component, and the next scheduled event value is not already set
For example, if a value is scheduled to be set to "true" in 1 hour but is already set to "true", no calculation is performed, even if the Start Enable or Stop Enable properties are set to "true".
The product of this calculation is the "Calculated Start Time" and the "Calculated Stop Time". The "Calculated Start Time" defines an early start command to achieve a specified temperature range by occupancy time. The "Calculated Stop Time" defines an early stop command without sacrificing the temperature range by unoccupancy time. After an optimized event is invoked, the actual area response (temperature change rate) is analyzed and weighted adjustments are made to the calculation parameters based on the detected values so that subsequent calculations might be more accurate.
Start time and stop time operations are described below:
Calculated Start Time
Only one optimized start sequence is performed per day. The following factors affect the Calculated Start Time calculation.
Temperature differential
If the space temperature is outside the range defined by the lower and upper comfort limits, the difference between the space temperature and the closer limit represents the number of degrees the mechanical equipment must make up during the prestart optimized period.
Run-time minutes
The run-time heating or cooling factors (depending on the direction the space temperature must move) are multiplied by the temperature differential to determine the number of run-time minutes required to achieve the comfort limit at occupancy time, as defined by the schedule's start time.
Optimum start time
When the system's time is later than the schedule's time offset by the calculated leadtime, the optimum start outputs are enabled.
The calculated leadtime is limited by either the "Earliest Start Time" or the "Max Earliest Start Hours" depending on the current setting of the "Start Limit Mode" property. If the "Calculated Start Time" is prior to the configured limit, the optimum start occurs at configured limit. An optimum start is performed only for the first scheduled start for the day.
Calculated Stop Time
You can perform multiple stop operations but no optimized stop can occur before the time specified by the Earliest Stop Time property.
Temperature differential
If the space temperature is inside the range defined by the lower and upper comfort limits and the schedule's status is active, the difference between the space temperature and one of the limits (depending on the mode) represents the number of degrees the temperature can drift between the time the mechanical equipment is stopped and the schedule's inactive event time.
Drift time
The drift (lead-time) calculation is similar to the one for Start Time but using the drift-time heating and cooling factors.
Optimum stop time
Optimum stop time is invoked for each of the schedule’s inactive events and is based on the drift time and Next Event Time value.
The OptStartStop component includes the following properties:
Status
BStatus slot which reflects the current status of the component.
Fault Cause
String property which stores the fault cause if the component's status is in fault.
Stop Calc Mode
This boolean property allows you to select either "Heat and Cool", "Cool Only" or the "Heat Only". The selected option applies only to optimized stop calculations which means that optimized stop calculations are performed only for the selected mode.
Parameter Reset Time
This property displays the time when any of the four runtime or driftime properties change to the User Defined values.
Start Enable
This property allows you to manually or automatically enable or disable the optimized start function.
Stop Enable
This property allows you to manually or automatically enable or disable the optimized stop function.
Schedule Status
This boolean property monitors and displays the status of the schedule that is linked to it.
Next Event Time
This property is linked to a schedule for the time of the next scheduled event.
Next Event Value
This property is linked to a schedule and reflects the value of the action for next scheduled event.
Outside Temp
This property is linked to outside temperature and displays the value for information only.
Space Temp
This property is linked to a space temperature output and displays the temperature of the area affected by equipment associated with the OSS component.
Start Time Command
This boolean property is an output that you link to a control for invoking an equipment start command. For example, it can be linked to a prioritized input of a boolean writable - or directly to the equipment Start control.
Stop Time Command
This boolean property is an output that you link to a control for invoking an equipment stop command. For example, it can be linked to a prioritized input of a boolean writable - or directly to the equipment Stop control.
Message
This field provides information that indicates the results of the latest start or stop command, the status of an optimized start analysis, or other possible messages. For example, the following message is displayed to indicate that an optimized stop has occurred: “Optimized stop for 14-Jun-07 5:18 PM EDT schedule time. Space temp is 75.0.”
Upper Comfort Limit
This property value is the Cooling mode target temperature.
Lower Comfort Limit
This property value is the Heating mode target temperature.
Comfort Deadband
This property value is a deadband applied to the upper and lower comfort limits when evaluating the effectiveness of the optimized start event.
Dynamic Parameter Adjust
This controls whether or not calculation parameters are programmatically adjusted after an execution. After the OSS component completes a start or stop control, if this property value is set to true
, the component evaluates the actual recovery rate (degrees/hour) and automatically adjusts the Runtime and Drifttime properties values so that they are influenced by actual drift time and run time.
Old Parameter Multiplier
This property is used to weight the dynamic parameter adjustment calculation. The value that you specify in this field affects how much weighting you assign to the previous runtime property value when it is used in the dynamic parameter adjustment calculation. A larger value increases the amount of weighting given to the previous runtime and a smaller value decreases the weighting.
Earliest Stop Time
This property allows you to specify a time, before which, no stop command may be issued. If this value is set earlier than the Calculated Stop Time, the Calculated Stop Time is adjusted to equal this time.
Start Limit Mode
This property defines whether the "Earliest Start Time" property or the "Max Earliest Start Hours" is used in the optimal start time calculation.
Earliest Start Time
The property allows you to specify a time, before which, no start command may be issued. If the Calculated Start Time is prior to this time, the Calculated Start Time is adjusted to equal this time. This prevents an optimal start event from occurring prior to this configured time.
Max Earliest Start Hours
The property allows you to specify the maximum number of hours prior to the scheduled occupancy which a start command may be issued. If the difference between the actual Next Event Time and the Calculated Start Time exceeds the Max Earliest Start Hours, then the Calculated Start Time is adjusted to match. If the Calculated Start Time results in a time prior to midnight, then the Calculated Start Time is set to midnight.
Drifttime Per degree Cooling
This property displays the actual value that is used for calculating an optimized stop time when the equipment is in cooling mode. This value is adjusted automatically if the Dynamic Parameter Adjust value is set to true
.
Drifttime Per degree Heating
This property displays the actual value that is used for calculating an optimized stop time when the equipment is in heating mode. This value is adjusted automatically if the Dynamic Parameter Adjust value is set to true
.
Runtime Per degree Cooling
This property displays the actual value that is used for calculating an optimized start time when the equipment is in cooling mode. This value is adjusted automatically if the Dynamic Parameter Adjust value is set to true
.
Runtime Per degree Heating
This property displays the actual value that is used for calculating an optimized start time when the equipment is in heating mode. This value is adjusted automatically if the Dynamic Parameter Adjust value is set to true
.
Last Start Time
This is a record of the last Start Time that was used for calculating an optimized start time. Since only one optimized start per day is allowed, this value does not display Start Times (restarts) that are subsequent to the initial Start Time for a day.
Last Stop Time
This is a record of the last Stop Time that was used for calculating an optimized stop time. Since multiple Optimized Stops are allowed in a day, this value changes to reflect the latest Optimized Stop time.
Outside Temp At Beginning
This is a record of what the outside air temperature was at the time of the last start or stop command. This is the temperature that was used in calculations for dynamic parameter adjustment.
Space Temp At Beginning
This is a record of what the space temperature was at the time of the last start or stop command. This is the temperature that was used in calculations for dynamic parameter adjustment.
Calculated Start Time
This field shows the calculated time for the next start command.
Calculated Stop Time
This field shows the calculated time for the next stop command.
Comfort Alarm
StatusBoolean property which indicates the effectiveness of the last optimized start event. If the space temperature at the scheduled time of occupancy was outside of the comfort band, the value is set to "alarm". The comfort band is defined as lowerComfortLimit - comfortDeadband and upperComfortLimit + deadband.
Program Mode
As part of the logic that the OSS component uses, there are five “program mode” states. These states serve primarily in logic control, however, they may be informative to the system engineer, as well. The Program Mode value displays the current heating or cooling state for optimized start or stop. The following list describes the possible display values and meanings.
0 (“No” Calculation)
This value indicates that no calculation is being made
1 (“Start” Calculation)
This valued indicates that the optimized start calculation process is ongoing but that an optimized start or stop is not yet in progress.
2 (“Start” in Process)
This value indicates that an optimized start has been initiated.
3 (“Stop” Calculation)
This value indicates that an optimized stop calculation process is ongoing but that an optimized start or stop is not yet in progress.
4 (“Stop” in Process)
This value indicates that an optimized stop has been initiated.
Mode
String slot that is equivalent of the Program Mode slot.