kitControl-OptimizedStartStop

The OptimizedStartStop 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 OptimizedStartStop component is available in the kitControl 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:

OptimizedStartStop operation

The OptimizedStartStop 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 Command Time”. The Calculated Command Time applies to both the Start Time and the Stop Time, as appropriate. Therefore, it defines an early start command to achieve a specified temperature range by occupancy time or an early stop command without sacrificing the temperature range by unoccupancy time. After a CalculatedCommand Time 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.
  If the calculated leadtime is so large that an optimum start time prior to midnight is the result, the optimum start occurs at midnight. 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.

OptimizedStartStop properties

The OptimizedStartStop component includes the following properties:

Heat Cool Mode

This boolean property allows you to enable either the heatMode or the coolMode. The selected option applies only to optimized stop calculations which means that optimized stop calculations are performed only for the selected mode. Optimized start calculations are performed for both heat and cool modes, regardless of this property value.
Parameter Reset Time

This property displays the time when any of the four runtime or driftime properties change to the User Defined values. The OSS component copies the user defined drifttime and runtime property values to the corresponding actual drifttime and runtime property 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.
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 Start Time

This property allows you to specify a time, before which, no optimized start command may be issued. If this value is set earlier than the Calculated Command Time, the Calculated Command Time is adjusted to equal this time.
Prior to AX-3.5, this property was unavailable, with its default 12:00:10 AM value (around midnight) effectively hardcoded. Now using this property, you can enter a later earliest start time.
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 Command Time, the Calculated Command Time is adjusted to equal this time.
Drifttime Per degree Cooling User Defined

This property allows you to set a default value for calculating the rate of drift in cooling mode. When you save a value to this field, the value is copied to the Drifttime Per Degree Cooling field.
Drifttime Per degree Heating User Defined

This property allows you to set a default value for calculating the rate of drift in heating mode. When you save a value to this field, the value is copied to the Drifttime Per Degree Heating field.
Runtime Per degree Cooling User Defined

This property allows you to set a default value for calculating the runtime value in cooling mode. When you save a value to this field, the value is copied to the Runtime Per Degree Cooling field.
Runtime Per degree Heating User Defined

This property allows you to set a default value for calculating the runtime value in heating mode. When you save a value to this field, the value is copied to the Runtime Per Degree Heating field.
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 Command Time

This field shows the calculated time for the next command. This could be a start or a stop command.
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.

Example 12. Using the OSS component for optimum start

Figure 37 shows an example wiresheet view of a simple use of an OSS component.

Figure 37. Using the OSS component: example - part 1

Note the following about this example:

A weekly schedule specifies occupancy times and is linked to the OSS component for calculations. The schedule is also linked directly (bypassing the OSS component) to the in16 property (lowest priority in this case) of the occupancy control point (AhuOccCmd).
The OSS component Start Enable and Stop Enable properties are both true, so that both Optimized starts and Optimized stops are enabled.
The Start Time and Stop Time commands are linked to priority inputs in12 and in13, respectively of the occupancy control point (AhuOccCmd). The Start Time and Stop Time commands are true when an optimal start or stop condition is required, otherwise the outputs are set to null which relinquishes control to the next higher priority level.

Figure 38 shows additional logic added to the example.

Figure 38. Using the OSS component: example - part 2

Additional logic is linked into the occupancy command component (AhuOccCmd) to control which logic has priority on specifying the “AhuOccCmm” boolean point status, as follows:
- in9 temperature control overrides a demand limiting link from an EDL component to in10. This prevents a load shed if the configurable comfort range is exceeded.
- in10 (demand limiting link from EDL component) overrides an OSS Stop link into in12
- in12 (OSS component Stop link) overrides a Start link into in13 (as described above)
- in13 (optimal start) overrides the schedule link to in16 (lowest priority) (as described above)

For related information, refer to ElectricalDemandLimit.