LX Series Unit Ventilator Controller User's Guide
53
Optimum Start
Optimum Start prepares the space for occupancy in advance of the occupied
period. If you start heating or cooling at the optimum time before the occupied
period begins, the UVC provides a comfortable space that is ready for occupancy
without wasting energy. Enable Optimum Start on the Options screen of the Unit
Ventilator Controller configuration wizard. Select the boxes labeled Enable
Optimum Start for heating and Enable Optimum Start for cooling.
The UVC maintains statistics that compare the outside temperature to the time
required for the space to reach the occupied setpoints. The UVC uses the statistics
to calculate the length of time required for Optimum Start.
Because the Optimum Start time is calculated every day for the current outside air
temperature, it is much more energy efficient than simply starting the occupancy
period before the actual arrival of occupants.
Enter a value in the Maximum start time box to limit the Optimum Start time
period. Optimum Start begins no sooner than the Maximum start time before the
occupancy change. For example, if the space enters the occupied mode at 8:00
A.M. and the Maximum start time is 30 minutes, then Optimum Start does not
begin until 7:30 A.M. at the earliest. Of course, Optimum Start can still begin at
any time that is less than 30 minutes before 8:00 A.M.; for example, 7:41 A.M.
When statistics are not available, you can choose from two options. The first
option starts heating or cooling when the space occupancy changes. The second
option allows Optimum Start to use the Maximum start time. To enable this
feature, select the box labeled
Use maximum time if no statistics
on the Options
configuration screen or set bit #58 of the network variable to UCPTobjectoptions.
Regardless of which setting you choose, the first samples are saved when the UVC
does not have any statistics; these samples include the outside air temperature and
the time required to reach the setpoint. Each day, Optimum Start uses the time
recorded from the previous day’s sample. For example, if the Unit Ventilator
Controller recorded that the space reached occupied setpoint in 25 minutes the first
day, then on the second day the UVC would begin Optimum Start 25 minutes
before occupancy. If a maximum start time has been entered, the UVC may use a
value derived from the samples that is less than the maximum start time. However,
the controller does not use a start time that is greater than the maximum start time
value.
On the third day, the UVC has two samples stored and uses the two samples to
calculate the Optimum Start time given the current outdoor temperature. From this
point on, all Optimum Starts are statistically calculated by the UVC using its saved
samples.
Requirements for Optimum Start
The next state and time to the mode must be defined in advance. There must be a
scheduler and the schedule must be properly bound to the Unit Ventilator
Controller using nviOccCmd.
